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PerspectiveAugust 15, 2022

Site-Selective Functionalization of C(sp³) Vicinal Boronic Esters
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Alma Viso
Alma Viso
Instituto de Química Orgánica General, IQOG-CSIC, Juan de la Cierva 3, 28006 Madrid, Spain
More by Alma Viso
https://orcid.org/0000-0003-2622-4777
Roberto Fernández de la Pradilla
Roberto Fernández de la Pradilla
Instituto de Química Orgánica General, IQOG-CSIC, Juan de la Cierva 3, 28006 Madrid, Spain
More by Roberto Fernández de la Pradilla
Mariola Tortosa*
Mariola Tortosa
Departamento de Química Orgánica and Institute for Advanced Research in Chemical Sciences (IAdChem), Universidad Autónoma de Madrid, Madrid 28049, Spain
*Email for M.T.: [email protected]
More by Mariola Tortosa
https://orcid.org/0000-0002-5107-0549

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ACS Catalysis

Cite this: ACS Catal. 2022, 12, 17, 10603–10620

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https://doi.org/10.1021/acscatal.2c02857

Published August 15, 2022

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Abstract

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Selective functionalization of the C–B bond in 1,2-bis(boronate) esters has emerged as a powerful tool to prepare 1,2-difunctionalized compounds with stereocontrol. Selective Suzuki cross-coupling, oxidation, amination, and homologation reactions serve as platforms to prepare a wide variety of compounds from a common intermediate. The exquisite selectivity offered and their easy preparation from feedstock material using a myriad of catalytic transformations make them attractive building blocks for the preparation of complex molecules. In this Perspective, we summarize the examples of selective C–B bond functionalization of vicinal bis(boronates), attending to the nature of the C–B bond functionalization.

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1. Introduction and Overview of Diboration Methods

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1,2-Bis(boronate) esters have attracted increasing interest as versatile building blocks in organic synthesis. The most interesting feature of this class of compounds is the possibility to selectively functionalize one of the two boryl moieties using a sequence of two reactions. The selective functionalization of one of the boronic esters, combined with the myriad of stereospecific transformations that can be envisioned with the second boryl unit, offers a powerful tool to build a wide variety of chiral compounds from a common intermediate. (1) The synthetic potential of these building blocks has stimulated the development of different catalytic strategies to prepare stereodefined 1,2-bis(boronate) esters (Scheme 1). Diboration of alkenes (paths a and c, Scheme 1) and alkynes (path b), carboboration of vinyl boronates (path d), and homologation reactions using lithiated carbamates and 1,1-diboryl methanes (path e) are the most common strategies to prepare these reagents.

Scheme 1. Synthetic Potential and Approaches to Prepare 1,2-Bis(boronate) Esters

Although the synthesis of 1,2-bis(boronic) esters has been included in different articles, (2−6) we realized that a review highlighting the synthetic opportunities that they enclosed was still missing. In this Perspective we want to offer an overview of the kinds of molecules that can be prepared through selective functionalization of 1,2-bis(boronates), including their use as synthetic intermediates in total synthesis. For this reason, this Perspective is organized according to the nature of the selective C–B bond functionalization and not according to the strategy used to prepare them. The different catalytic methods used to prepare the 1,2-bis(boronates) will be discussed before describing a particular functionalization.

2. Site-Selective Functionalization of 1,2-Bis(boronates)

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In this section, we will examine site-selective reactions gathered from the recent literature. In many cases, the selectivity in these transformations arises not only from differences in steric hindrance but also from boron activation promoted by the presence of a vicinal boronate that increases the Lewis acidity of the reacting boron atom. The different examples have been classified according to the nature of the selective C–B bond functionalization.

2.1. Suzuki–Miyaura Cross-Coupling

Among the different selective functionalizations of 1,2-diboron compounds reported, the selective Suzuki–Miyaura cross-coupling is undoubtedly the most studied transformation. In most cases, the vicinal bis(boronates) are generated by diboration of terminal alkenes to provide compounds in which one boryl unit is attached to a secondary carbon and the other boryl moiety is on a primary carbon. In this scenario, the less hindered primary boronate reacts preferentially with a Pd(II) complex in the transmetalation step of the Suzuki–Miyaura cross-coupling. Starting with enantioenriched 1,2-diboron compounds, enantioenriched cross-coupling products can be prepared. Therefore, the progress in selective cross-coupling reactions has been connected to the development of catalytic enantioselective diboration methodologies.

The first selective Suzuki–Miyaura cross coupling of 1,2-diboron compounds was reported by Morken in 2004. In this study, the authors reported a single-pot tandem diboration/Suzuki-cross-coupling reaction of terminal alkenes (Scheme 2). (7) The enantioenriched 1,2-diboronates were prepared through enantioselective rhodium catalyzed diboration using B₂cat₂ and (S)-Quinap as a chiral ligand. The catechol boronic esters were too labile to be isolated and were subjected to in situ cross-coupling using (dppf)PdCl₂ as the catalyst with different aryl bromides. The authors proposed that the more accessible C–B bond would react more quickly, leaving the secondary bond available for further transformations. After oxidation of the secondary C–B moiety, they observed that the enantiopurity was unaltered during the process. The limitation of this approach is that good enantioselectivity in the diboration step was only obtained for bulky aliphatic alkenes.

Scheme 2. Single-Pot Asymmetric Diboration/Suzuki Coupling

A few years later, the Fernández group reported the one-pot diboration/Suzuki cross-coupling of terminal alkenes using a Pd catalyst and B₂cat₂ as the boron source (Scheme 3). (8) They observed that, after completion of the diboration, the addition of aryl halides and aryl triflates provided complete monoarylation of the primary alkylboronic ester. Finally, an oxidative workup led to the formation of the corresponding carbohydroxylated products. Remarkably, only 5 mol % of the palladium catalyst was required to undergo both sequences: the borylation and the cross-coupling reaction. In this case, the enantioselective Pd-catalyzed diboration was not studied.

Scheme 3. Pd-Catalyzed One-Pot Diboration/Cross-Coupling of Alkenes

In 2009, Hoveyda and co-workers reported the first selective cross-coupling of a 1,2-bis(pinacol) boronate obtained from copper-catalyzed enantioselective diboration of an alkyne (Scheme 4). (9) The reaction is site-selective for the less-hindered C–B bond, and after oxidation they proved that the product was obtained without loss of enantiomeric purity. The use of pinacol derivatives instead of catechol esters in the selective cross-coupling is a significant step forward, as it allows for the isolation of the 1,2-diboron compounds and the monoborylated cross-coupling product. Although in this publication the authors only did an in situ oxidation of the internal boryl moiety, the use of pinacol esters opens the door to design further functionalizations of the second boryl unit.

Scheme 4. Selective Cross-Coupling of Bis(boronates) Obtained from Alkynes

In an elegant approach, the Morken group reported in 2014 the asymmetric synthesis of a wide array of molecules from terminal alkenes by cascades of platinum-catalyzed enantioselective diboration and cross-coupling of the primary pinacol boronate moiety (Scheme 5). (10) This methodology provides a powerful strategy for formal enantioselective carbohydroxylation, carboamination, and bisalkylation of terminal alkenes. Several olefins were successfully engaged in the tandem transformation, affording the products in good yield and with high enantioselectivity. Importantly, substrates containing stereocenters provided the products with excellent diastereomeric ratio. Additionally, the cascade reaction occurred efficiently with vinyl chlorides to afford homoallylic alcohols with stereodefined cis- and trans-alkenes after oxidative workup (Scheme 5a). The selective cross-coupling has been successfully combined with an amination or Matteson homologation reaction on the secondary boronate for the enantioselective syntheses of (S)-N-Boc-amphetamine, the morpholine-derived fungicide (S)-fenpropimorph and anticonvulsant (S)-pregabalin (Lyrica) among other products (Scheme 5b).

Scheme 5. Tandem Pt-Catalyzed Diboration/Selective Cross-Coupling/Oxidation

The authors proposed that the function of the secondary boron atom might be to act as a Lewis acid, coordinating to the pinacolate oxygen of the neighboring boron center, thereby enhancing the boron Lewis acidity and therefore its reactivity (Scheme 5c). In order to collect evidence to support this explanation, the Pd-catalyzed cross-couplings of aliphatic mono- and 1,2-, 1,3-, and 1,4-bis(boronates) were compared and, after an oxidation step, only the 1,2-bis(boronate) gave a good conversion (91%). Additionally, the cross-coupling of an isotopically labeled 1,2-diboronate and chloroisobutylene took place with retention of the configuration at the deuterium-containing stereocenter, which suggested an inner-sphere transmetalation in the catalytic cycle (Scheme 5d).

One year later, the same research group reported a complementary approach to selectively functionalize the secondary boronic ester of vicinal diboron compounds incorporating a hydroxyl moiety as the directing group. (11) Complexation of the homoallylic alcohol with Pd guides the transmetalation step to the secondary boronate. This protocol, along with the reported hydroxyl-directed diboration, constitutes a powerful methodology for regio- and stereoselective functionalization of homoallylic alcohols. (12) Sequential directed metal-free diboration/cross-coupling, followed by protection of the directing hydroxy group, furnishes δ-oxygenated boronates from a wide range of substrates. Importantly, the reaction works well with terminal alkenes, internal olefins, and trisubstituted alkenes. While terminal and internal olefins furnish 1,3-syn relative stereochemistry, trisubstituted alkenes furnish modest 1,3-anti induction (Scheme 6a). These results are in line with the observations for the directed diboration reactions. Finally, they demonstrate the utility of the directed cross-coupling with the synthesis of different biologically active compounds, such as debromohamigeran E (Scheme 6b).

Scheme 6. Tandem Base-Induced Diboration/Hydroxyl-Directed Cross-Coupling/Oxidation

This research group has also accomplished the enantioselective diboration of alkenes catalyzed by carbohydrate-derived glycols, available from inexpensive precursors by efficient procedures, that can be applied to a broad scope of alkenes and in scales of up to 10 g (Scheme 7). (13) This diboration method uses bis(neopentylglycolato)diboron (B₂neo₂) as the boron source, which enables the exchange by the chiral glycols. The diboration can also be coupled with the tandem Pd-catalyzed cross-coupling and oxidation to render enantiopure secondary alcohols from simple terminal olefins.

Scheme 7. Tandem Carbohydrate-Catalyzed Diboration/Hydroxyl-Directed Cross-Coupling/Oxidation

Finally, by combining these strategies, a broad variety of different compounds can be prepared from a common intermediate and this constitutes a powerful tool for the synthesis of complex molecules. An interesting example is the enantioselective synthesis of the cytotoxic macrolide arenolide, (14) that allowed the stereochemical assignment of the natural product (Scheme 8). The tandem enantioselective diboration/Pd cross-coupling protocol is used multiple times throughout the synthetic sequence, showing the versatility of vicinal boronates.

In 2017, Meek reported an elegant approach to prepare enantioenriched hydroxy bis(boronates) in good yields and excellent anti:syn ratios. (15) This transformation starts with the copper-catalyzed enantioselective borylcupration of vinyl boronates in the presence of a chiral diphosphine to form a transient α-boryl-Cu nucleophile that adds to an aldehyde (Scheme 9). An intramolecular version of this method, in substrates that contain both the vinyl boronate and the aldehyde or ketone, is useful for the stereo- and enantioselective synthesis of functionalized tetrahydronaphthalenes, cyclopentanes, and piperidines with vicinal bis(boronates). The two boryl moieties could be selectively functionalized through a Pd-catalyzed cross-coupling followed by deborylative thienylation or amination, increasing the synthetic value of this method.

Scheme 9. Cu-Catalyzed Tandem Borylation/C═O Addition and Site-Selective Functionalization

Recently, the Marder group has developed conditions for the direct diboration of alkyl bromides, iodides, and tosylates, presumably precursors of transient alkenes that undergo the transition-metal-free addition of bis(catecholato)diboron, B₂cat₂ (Scheme 10). (16) Interestingly, other common bis(boronic) esters such as B₂pin₂ and B₂neo₂ did not produce the expected racemic 1,2-bis(boronates). Also, the use of KI and DMA plays an important role in the elimination to the (E)-alkene intermediate that then undergoes syn-diboration. The scope of the reaction is quite general with good results from benzyl, alkyl, secondary and tertiary halides and tosylates. Similarly, the diboration protocol can be applied to tertiary alcohols and it has also been carried out onto a number of skeletons related to natural products. Besides, high chemoselectivity was exhibited in a competition experiment with secondary over primary alkyl bromide carbon positions. Additionally, some applications of site-selective transformations have been examined for these 1,2-bis(boronic) esters such as a sequential alkyl bromide diboration/Suzuki–Miyaura cross-coupling/oxidation that can be directly carried out onto the 1,2-bis(boronic) catecholate, skipping the pinacol esterification step.

Scheme 10. Transition-Metal-Free Diboration of Alkyl Halides and Tosylates with Bis(catecholato)diboron and Site-Selective Transformations of Vicinal Boronates

In 2021 Martin reported a different approach to prepare 1,2-bis(boronates) using a nickel catalyst, a diboron compound, and α-haloboronates (Scheme 11). (17) The reaction takes place through insertion of the olefin into the in situ generated LnNi-Bpin complex followed by 1,2-[Ni] migration to the terminal position and final cross-coupling with the haloboronate. Remarkably, the method can be applied to simple ethylene. Subsequently, the bis(boronates) were submitted to site-selective Suzuki–Miyaura cross-coupling at the less substituted C–B bond with ArBr and vinyl chlorides using Pd(OAc)₂ and RuPhos.

Scheme 11. Sequential Ni-Catalyzed Synthesis of 1,2-Bis(boronates)/Suzuki–Miyaura Cross-Coupling

Remarkably, the selective Suzuki–Miyaura cross-coupling can also be applied to small cycles where the vicinal bis(boronates) are both secondary. In this context, Marder, Wu, and co-workers reported (18) the synthesis of cyclopropyl 1,2-bis(boronates) through the copper-catalyzed carbonylative cyclopropanation of terminal alkenes (Scheme 12a). They also reported some examples of selective Suzuki–Miyaura cross-coupling of cyclopropyl 1,2-bis(boronates) where both boronic esters are secondary. The products were obtained in good yield and with exquisite selectivity, leaving the other boryl moiety intact. An alternative and recent approach to racemic cyclopropyl-1,2-bis(boronates) has been reported by the Ghosh and Berrée group, (19) using a Simmons–Smith cyclopropanation of alkenyl-1,2-bis(boronates). The resulting cyclopropanes (Scheme 12b), which contain both secondary and tertiary boronic esters, render regioselective Suzuki–Miyaura cross-coupling at the secondary position. Interestingly, the authors also include one example of regioselective Suzuki–Miyaura for cyclopropyl 1,2-bis(boronates) having two tertiary boronic esters.

Scheme 12. Site-Selective Cross-Coupling of Cyclopropyl Bis(boronates)

In 2021, the Tortosa group reported the base-promoted diboration of spirocyclobutenes. (20) The products are spirocycles with two boryl moieties that can serve as orthogonal exit vectors through selective C–B bond functionalization (Scheme 13a). Interestingly, the regioselective Suzuki–Miyaura cross-coupling can discriminate between two different secondary boronic esters with no directing groups in the spirocyclobutane system. The transmetalation occurred selectively on the external boryl unit with retention of the configuration in the newly formed stereocenter. The optimal conditions for the cross-coupling require the use of a 1:2.5 ratio of Pd to ligand to avoid an undesired β-boryl elimination side reaction. This is a highly general process useful for the assembly of libraries of functionalized spirocyclobutanes. The authors developed as well a Pt-catalyzed enantioselective diboration using a phosphonite as a chiral ligand. This approach afforded a number of novel enantioenriched spirocyclobutane bis(boronates) (Scheme 13b).

Scheme 13. Diboration-Selective Cross-Coupling of Spirocyclobutenes

In 2016, Crudden described the orthogonal cross-coupling of benzylic and nonbenzylic 1,2-diboronates (Scheme 14). (21) The vicinal diboronates were prepared through enantioselective rhodium-catalyzed diboration using a chiral bis(oxazoline) ligand. The primary C–B bond in the products could be selectively functionalized with different aryl bromides, including electron-rich, electron-poor, and π-extended substrates. For the next step of the sequence, the benzylic C–B bond was coupled using the previously described silver oxide promoted conditions reported by the same research group. (22) The 1,1′,2-triarylated products were obtained with up to 92% enantiospecificity. This methodology was efficiently applied to the synthesis of the phosphodiesterase inhibitor CDP 840.

Scheme 14. Chemoselective Cross-Coupling Reaction of Chiral 1,2-Bis(boronic) esters: Application to the Synthesis of CDP 840

An intramolecular version of the above protocol was recently reported. Morandi and co-workers developed a cascade Suzuki–Miyaura cross-coupling of 1,2-bis(boronic) pinacol esters with 2,2′-dihalo-1,1′-biaryls to afford 9,10-dihydrophenanthrenes (Scheme 15). (23) Using biaryls with an unsymmetrical substitution pattern full site selectivity was observed. Furthermore, this cross-coupling of an alkyl 1,2-bis(boronic) pinacol ester proceeds through the challenging coupling of a secondary boronate with complete stereoretention.

Scheme 15. Double Suzuki–Miyaura Cross-Coupling of Vicinal Bis(boronic) Esters

2.2. Reactions Based on 1,2-Shift of Boronates

Besides transition-metal-catalyzed cross-coupling reactions, the most common reactions of boronic esters entail the coordination of the boron atom to a Lewis base, followed by a stereospecific 1,2-migration of the boronate. There are a few examples in the literature that follow this strategy and allow for the selective functionalizations of 1,2-bis(boronic) esters to transform the C–B bond into C–O, C–N, C–H, or C–C bonds in the new molecules.

In a recent report Morken and co-workers described the first site-selective oxidation of 1,2-bis(boronic) propanediolates. (24) They proposed that after coordination of the oxidant, if the 1,2-boronate rearrangement is the rate-limiting step and coordination of the oxidant to boron is reversible, then the more substituted electron-rich carbon may migrate preferentially, providing selective oxidation at the secondary boryl moiety (Scheme 16). A wide number of alkenes were examined in the tandem carbohydrate-catalyzed enantioselective diboration/mono-oxidation sequence, providing 1,2-hydroxy boronates in good yields and high enantiomeric ratios.

Scheme 16. Selective Oxidation of 1,2-Bis(boronic) Esters

The selective oxidation of a boronic pinacolate moiety was also reported in 2019 by Ooi. (25) In this work the starting material was a doubly borylated cyclopropane with two differentially protected boryl groups Bpin and BMIDA (MIDA: N-methylimidodiacetate) that was synthesized by a photocatalyzed borylcyclopropanation of α-MIDA-boryl styrenes with diiodoborylmethane under visible-light irradiation using 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN) as the catalyst (Scheme 17). Then upon treatment with MMPP in DMF, the Bpin group was selectively oxidized in good yield and without loss of diastereomeric ratio, leaving the BMIDA moiety intact.

Scheme 17. Selective Oxidation of Pinacol-Boronate Moiety

Another example of selective oxidation of a pinacol boronate moiety in the presence of a boronamide was reported by Yun. (26) Starting from a vinylboronamide (1,8-diaminonaphthylboronamide, Bdan), a Cu/Pd-catalyzed enantioselective arylboration provided anti 1,2-diboryl compounds with the two boryl moieties being differentiated (Scheme 18). Then, selective functionalizations of the vicinal bis(boron) compounds were examined, taking advantage of the lower Lewis acidity of Boron in Bdan compared with Bpin. Chemoselective transformation of Bpin to a potassium trifluoroborate and to a hydroxyl group by oxidation took place with moderate yields. However, other procedures such as a Zweifel olefination or amination were not selective on these substrates.

Scheme 18. Enantioselective Addition of LCu-Bpin to Alkenyl Boron: Pd-Catalyzed Cross-Coupling and Selective Transformations of Bpin in the Presence of Bdan

An interesting example of functionalization of bis(boronic) esters was reported by the Tortosa group, allowing for the regioselective oxidation and amination of spirocyclobutanes containing two secondary bis(boronates) (Scheme 19). (20) Site-selective oxidation takes place at 0 °C, using 1 equiv of H₂O₂, through coordination of the Lewis base with the less hindered boron atom in an equatorial arrangement (I), thus avoiding 1,3-axial interactions and selectively installing an OH group at the external carbon. Conversely, selective amination takes place under harsher conditions, at 60 °C with methoxyamine/KO-t-Bu. The authors proposed a reversible coordination of the Lewis base with the boron atoms, followed by faster 1,2-migration of the internal borate complex (II) that releases more steric strain, yielding the spirocyclobutane with the NH₂ group at the internal position.

Scheme 19. Selective Oxidation and Amination of 1,2-Bis(boronic) Esters

Within this context, a Lewis base induced 1,2-shift of boronates has also been applied successfully to the construction of nitrogenated heterocycles. In 2021, the Morken group described (27) a chemoselective intramolecular amination of vicinal bis(boronic) esters with a methoxyamino group at a suitable distance in the carbon chain (Scheme 20). In fact, this distance is critical in the size of the resulting aza-cycle. Azetidines, pyrrolidines, and piperidines are available through this 1,2-metalate shift of an aminoboron “ate” complex having another boronic ester as an additional handle for further transformations of the molecule.

Scheme 20. Chemoselective Intramolecular Amination of Vicinal Bis(boronic) Esters

In 2016, the Aggarwal group reported the selective homologation of optically active 1,2-bis(boronic) esters by using enantioenriched primary or secondary lithiated carbamates or benzoates (DG) to afford 1,3-bis(boronic) esters, which can be oxidized to the corresponding 1,3-diols with full stereocontrol (Scheme 21). (28) They propose that the less hindered primary boronic ester reacts in preference to the secondary boronic ester. Moreover, they found that the selectivity is highly dependent on the nature of the nucleophile. This methodology was applied to the total synthesis of the 14-membered macrolactone Sch725674. Also a related approach has been used by this group to accomplish the total synthesis of the antimalarial bastimolide B, a complex macrolide isolated from marine cyanobacteria. (29)

Scheme 21. Selective Homologation of 1,2-Bis(boronic) Esters

In 2019 Nogi and Yorimitsu described the diborative reduction of internal alkynes using B₂pin₂, Na, and LiI that after protic workup gave rise to secondary vicinal bis(boronates). (30) The anti:syn stereoselectivity depends on the nature of the substituents and also on the protonation agent (Scheme 22). In this publication the authors demonstrated that one of these syn-bis(boronates) can be selectively transformed through a stereoretentive arylation with 1 equiv of 2-thienyllithium/NBS of one of the boronates and subsequent oxidation of the remaining boron atom.

Scheme 22. Diborative Reduction of Alkynes and Selective Boronate Transformations

2.3. Selective Homolytic Cleavage of a C–B Bond

The selective transformation of a 1,2-diboronate through homolytic cleavage of the C–B bond has remained an unexplored challenge until recently. In 2019, the Aggarwal group reported the selective functionalization of the secondary boryl moiety of 1,2-bis(boronic) esters through a photocatalyzed C–B bond functionalization. (31) The reaction requires the selective preformation of a borate complex between an aryllithium and the primary boronic ester of a 1,2-diboronate. Single-electron oxidation of the borate complex promoted by a photocatalyst leads to the formation of a primary β-boryl radical that undergoes a fast 1,2-boron shift to the thermodynamically favored secondary radical. Then, functionalization of the carbon-centered radical with different radical acceptors takes place with yields up to 98% (Scheme 23). This groundbreaking approach will undoubtedly inspire future selective functionalizations.

Scheme 23. Selective Functionalization of 1,2-Bis(boronates) Using Photoredox Catalysis

Following a similar strategy, the same group reported the arylation of 1,2-diboronates. In this study, (32) the primary radical is formed through a photoinduced electron transfer (PET) between the electron-rich aromatic ring of the boronate intermediate (formed from 4-(dimethylamino)phenyllithium) and an electron-deficient (hetero)aryl nitrile (Scheme 24a). After a 1,2-shift boron migration, similar to that described above, the arylation of secondary boronates takes place, which is complementary to the Suzuki–Miyaura cross-coupling that, in contrast, produces arylation at the primary boronate. In some cases, the use of heteroaryl nitriles requires a catalyst (4CzIPN, 5 mol %) for better yield. Interestingly, the procedure has been applied to cyclopentane and cyclohexane cis-1,2-bis(boronates), yielding trans-arylation products for both substrates, unlike the Suzuki–Miyaura cross-coupling that renders the cis-arylated diastereoisomers (Scheme 24b). In a later development of this group, (33) the generation of the secondary radical from 1,2-bis(boronates) can be merged with a dual nickel/photoredox-catalyzed cross-coupling, expanding the scope from (hetero)aryl nitriles to (hetero)aryl bromides (Scheme 24c). Remarkably, starting from vicinal bis(boronates), this methodology allows for arylation of the more substituted boronic ester (secondary or tertiary) and it is complementary to arylation of the less hindered primary boronic ester by means of a Suzuki–Miyaura cross-coupling.

Scheme 24. Photocatalyzed Radical-Mediated Monodeboronative Arylation of Secondary Boronates

2.4. Selective Elimination (Boro-Wittig Reaction)

In 2016 Uchiyama and Hirano reported a method (34) for the preparation of allylic boronates in moderate to good yields that comprised one-pot diboration of tertiary allylic alcohols mediated by base followed by an in situ boro-Wittig elimination to give allylic boronates (Scheme 25). DFT calculations suggested the formation of a bis(boronate) intermediate that was also observed by ESI-MS when the reaction was performed at lower temperature (70 °C) instead of the direct formation of an allylic boronate that evolves through a Zimmerman–Traxler type six-membered cyclic transition state.

Scheme 25. Synthesis of Allylic Boronates from Tertiary Allylic Alcohols via Base-Mediated Diboration/Boro-Wittig Elimination

A related example of boro-Wittig elimination was described by Meek in 2019. (35) The work of this group describes the first examples of boron-hydroxyl elimination promoted by Martin’s sulfurane on [5,5]-bicyclic hydroxy 1,2-diboronates prepared by enantio- and diastereoselective desymmetrization of 2,2-disubstituted 1,3-diketones. The sequence starts with a Cu-catalyzed alkyne protoboration followed by borylative cyclization (Scheme 26). The stereochemical outcome of the desymmetrization/cyclization process is highly dependent on the nature of the substituents (R = Me or larger). Upon treatment with Martin′s sulfurane, [6,5]-bicyclic hydroxy 1,2-bis(boronates) suffer dehydration to render alkenyl boron bicycles while allylic boronates are generated in moderate to good yields from [5,5]-bicyclic hydroxy 1,2-bis(boronates) by a boro-Wittig elimination. The allylic boronate formed from the [5,5]-derivative can react with formaldehyde to give a bicycle with two contiguous quaternary stereocenters. The nature of the bicycle is a crucial element for the outcome of the elimination. The different reactivity arises from the better alignment between the C–B σ-bond and the carbocation p-orbital in the [5,5]-bicycle than in the [6,5]-analogue.

Scheme 26. Copper-Catalyzed Borylative Desymmetrization/Cyclization for the Synthesis of Bicyclic Hydroxy Bis(boronates) and Elimination Reactions

2.5. Boronate Allylation of Carbonyl Compounds

1,2-Bis(boronates) having a double bond at C-3 can be selectively functionalized through an allylic addition of the secondary allylic boronic ester to carbonyl compounds followed by a second transformation of the remaining primary boronic ester using any known protocol for oxidation, homologation, etc.

In 2012, Morken reported that Pt(dba)₃ catalyzes 1,2-diboration of cis-1,3-dienes using a chiral phosphonite as a ligand to deliver enantiomerically enriched 1,2-bis(boronates). (36) These substrates contain an α-chiral allylboronate and a cis-alkene, two structural motifs that in principle would produce a highly stereoselective allylation of carbonyl compounds (Scheme 27). Accordingly, several examples in this work illustrate the asymmetric allylboration of aldehydes that can be coupled with reactions on the newly formed terminal allylic boronate such as an oxidative workup to furnish an allylic alcohol, a Matteson homologation to give the homoallylic alcohol, or a protodeboronation to render the terminal alkene.

Scheme 27. Stereoselective Allylation of Aldehydes with 3-Ene-1,2-bis(boronates)

A year later, the same group described an extension of this methodology (37) that comprises a tandem enantioselective 1,3-diene diboration followed by double allylation of dicarbonylic compounds such as 1,4-dialdehydes. The methodology was applied to the synthesis of pumilaside B aglycon (Scheme 28).

Scheme 28. Enantioselective Synthesis of Pumilaside Aglycon

Within this context, in 2021 the Chen group published their work on the allylboration of aldehydes using α-borylmethyl crotylboronates (Scheme 29). Initial Pt(II)-catalyzed enantioselective diboration of 1,4-pentadiene followed by Ru-catalyzed alkene transposition led to almost enantiopure α-borylmethyl (E)-crotylboronates. (38) These bis(boronates) are submitted to a stereoselective Lewis acid catalyzed allylation of aldehydes that proceeds through a Zimmerman–Traxler transition state and after oxidative workup leads to (E)-γ-hydroxymethyl-anti-homoallylic alcohols. A parallel protocol, using a Ni(II) complex to isomerize the double bond, rendered enantioenriched α-borylmethyl (Z)-crotylboronates. (39) The reaction of these (Z)-crotylboronates proceeds with high stereoselectivity in the absence of a Lewis acid with simple aromatic and aliphatic aldehydes, rendering (E)-γ-hydroxymethyl-syn-homoallylic alcohols. The reactivity with chiral enantioenriched aldehydes was also examined, and the behavior found was consistent with a double-diastereoselection scenario.

Scheme 29. Synthesis and Reactivity with Aldehydes of α-Borylmethyl-(*E/Z*)-crotylboronates

The same group has described another asymmetric approach to these reactions. (40) Thus, using each of the enantiomers of a chiral phosphoric acid based on binol as acidic catalysts, (S)-A and (R)-A, the addition of (S)-α-borylmethyl-(E)-crotylboronate to aldehydes was stereodivergent, yielding after oxidation (4S,5S,Z)- and (4R,5R,E)-diols, respectively (Scheme 30). A formal synthesis of ACRL Toxin IIIB has been accomplished using this methodology from (R)-α-borylmethyl-(E)-crotylboronate and an α,β-unsaturated aldehyde.

Scheme 30. Enantiodivergent Allylation of Aldehydes Using α-Borylmethyl-(E)-crotylboronates

Finally, the kinetic resolution of racemic allylic 1,2-diboronates was examined as a method to accomplish the synthesis of 1,5-diols (Scheme 31). (41) An excess of racemic α-borylmethyl-(E)-crotylboronate was submitted to the allylation of a number of aldehydes, in the presence of the chiral phosphoric acid (S)-A to produce good yields of (Z)-γ-hydroxymethyl-anti-homoallylic alcohols with a good E:Z ratio (from 6:1 to 20:1) and high enantioselectivity. Aromatic, aliphatic, and α,β-unsaturated aldehydes were tested with good results in this kinetic resolution that represents an advantage of the methodology, since it eliminates the need for an initial enantioselective diboration reaction.

Scheme 31. Kinetic Resolution of α-Borylmethyl (E)-crotylboronate

In 2021 the Brown group described the enantioselective synthesis of 1,2-diboron derivatives with different substitution (Bpin and Bdan) at the boron atoms, as well as their application as double-allylation reagents for the diastereoselective synthesis of polysubstituted 1,4-diols (Scheme 32). (42)syn- and anti-bis(boron) compounds were available through Cu/Pd-catalyzed alkenylboration of (E)- and (Z)-vinylboronamides (Bdan). The authors found that the alkenylboration reaction is stereospecific when IPrCuCl/Xphos-PdG3 are used, likely via an initial B–Cu syn addition to the vinylboronamide followed by a stereoinvertive cross-coupling transmetalation of the alkyl copper intermediate with the palladium catalyst. Some examples of the enantioselective version of this reaction, from (Z)-styrylboronamide and using a chiral NHC-Cu complex and JackiePhos-NMe₂ or P(i-Bu)₃ as a ligand, are also included. The double-allylation protocol was then addressed through initial allylation of the less reactive allylboronamides in the presence of BF₃·Et₂O that presumably increases the Lewis acidity of boron by coordination to the nitrogen atoms. Under these conditions the allylation of aromatic and aliphatic aldehydes proceeds in good yields and stereoselectivities, generating a second allylboronate within the molecule. Notably these are the first examples of allylations with allylboronamides. After protection of the secondary OH group the subsequent stereoselective allylation of benzaldehyde takes place in the absence of a Lewis acid. The stereochemical outcome of these allylations can be rationalized through Zimmerman–Traxler transition states.

Scheme 32. Synthesis and Application of Double-Allylation Reagents for the Synthesis of 1,4-Diols

2.6. Miscellaneous Selective Transformations of 1,2-Diboronates

In this section we highlight those examples of selective functionalization of 1,2-diboronates that did not fit in any of the categories described above. One useful transformation that has not been discussed before is protodeboronation. In 2017, Aggarwal reported the enantioselective synthesis of primary–tertiary vicinal bis(boronic) esters by homologation of diborylmethane with an enantiopure (S)-1-arylethanol-derived lithiated carbamate (Scheme 33). (43) Afterward, they examined one example of the selective protodeboronation at the tertiary benzylic boronic ester that left unaltered the primary boronate but produced a significant loss of enantiomeric ratio (88:12 er). Also in a single step, the selective benzylic protodeboronation can be coupled to the Suzuki–Miyaura cross-coupling of the primary boronic ester. For this example, the degree of chirality transfer was not reported.

Scheme 33. Homologation of 1,2-Bis(boronic) Esters with Secondary Benzylic Carbamates and Regioselective Protodeboronation

In the context of selective functionalization of cyclopropyl 1,2-bis(boronates) Marder, Wu, and co-workers reported a selective silver-catalyzed protodeboronation and bromination. (18) In both cases, the products were formed in good yields with excellent diastereocontrol (Scheme 34).

Scheme 34. Selective Protodeboronation and Bromination of Cyclopropyl Bis(boronates)

In 2021, Qing and co-workers implemented an alternative protocol for the diboration of 2-vinyl naphthalenes by an electrochemical synthesis using an excess of HBpin, under a constant current of 20 mA, with 20% nBu₄NBF₄ as the supporting electrolyte and CH₃CN as the solvent within an undivided cell equipped with two Pt electrodes. (44) This diboration reaction takes place exclusively for 2-vinyl naphthalenes, since most of the styrene derivatives produced substantial amounts of hydroboration products (Scheme 35). To demonstrate the synthetic utility of this method, the electrochemical diboration was performed on a 10 mmol scale in 85% yield. Then, regioselective protodeboronation of naphthyl bis(boronate) induced by NaO-t-Bu took place at the benzyl site, leading smoothly to the primary boronic ester. Also, alkylative deborylation using NaO-t-Bu and allyl bromide allowed for the selective introduction of an allylic chain at the benzylic position, building a quaternary carbon in a moderate 45% yield.

Scheme 35. Electrochemical Diboration of Vinyl Naphthalene and Reactivity of Secondary Benzylic Boronate

Finally, the Morken group has recently reported an example of a regioselective copper-catalyzed protodeboronation of a 1,2-bis(boronate) available through a carbohydrate-catalyzed diboration. (45) The protodeboronation reaction takes place exclusively at the primary boronate, leaving intact the secondary boron atom for a second copper-catalyzed acylation to render a compound that was easily transformed into an anti-HIV analogue of galbulin (Scheme 36).

Scheme 36. Regioselective Copper-Catalyzed Protodeboronation

3. Site-Selective Functionalization of Vicinal C(sp³) Poly(boronic) Esters

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In 2012, Fernández and co-workers reported an interesting example of the straightforward cross-coupling reaction of 1,2,3-vicinal triborated species with aryl iodides (Scheme 37). The synthesis of the 1,2,3-tris(boronates) was accomplished by base-induced boration of dienes. Then, they observed that the internal C–B bond reacted selectively to form a new C–C bond by Pd-catalyzed Suzuki–Miyaura cross-coupling with moderate yields. (46) The authors proposed that the origin of the unexpected regioselectivity could be due to a double assistance of the two vicinal boryl moieties increasing the Lewis acidity of the internal boronic ester. 1,3-Diols can be obtained by combining the site-selective cross-coupling with a further oxidation.

Scheme 37. Site-Selective Suzuki–Miyaura Cross-Coupling in 1,2,3-Tris(boronates)

Morken reported in 2014 the Pt-catalyzed enantioselective diboration of vinyl boronates to obtain optically active 1,1,2-tris(boronates). (47) In the presence of a Lewis base, these chiral tris(boronates) act as highly reactive nucleophiles due to a double stabilization of the α-boryl carbanion by the vicinal boronic esters (Scheme 38). Consequently, regioselective deborylative alkylation using NaO-t-Bu in toluene provides access to a wide array of 1,2-diols, after oxidative workup, in a diastereoselective fashion, with the syn isomer being the predominant product in all cases. The method works efficiently with different primary and secondary electrophiles, giving the products in high yields and diastereomeric ratios. This methodology can be coupled to stereoretentive oxidation or Matteson homologation reactions, furnishing stereoselectively enantioenriched c-hexane derivatives. An efficient approach to a vicinal diol that was previously used as an intermediate in the synthesis of exo-brevicomin has also been accomplished by this method.

Scheme 38. Synthesis of 1,1,2-Tris(boronates) and Regioselective Deborylative Alkylation

Alternatively, racemic 1,1,2-trisboronates have been prepared directly from alkynes by transition-metal-free polyboronation by the Song group. (48,49) The nature of both the solvent and base are crucial for the outcome of the borylation. While Cs₂CO₃/CH₃CN leads to 1,2-bis(boronates), the use of K₂CO₃/Et₂O renders 1,1,2-tris(boronates) that presumably are the intermediates in the formation of 1,2-bis(boronates) via a domino-borylation-protodeboronation process (Scheme 39). Additionally, these 1,1,2-tris(boronates) can suffer site-selective base-induced protodeboronation, rendering bis- or mono(boronates) based on the base/solvent pair used. The regioselectivity found in these two examples is probably due to the stabilization of α-boryl and benzylic carbanions. (50)

Scheme 39. Base-Induced Borylation and Protodeboronation

In 2019 Nagashima and Uchiyama reported the photoinduced synthesis of tetraboronates from terminal alkynes, n-BuLi, and bis boron(pinacolate) under mild conditions with good yields (Scheme 40). The borylation reaction can be merged with base-promoted selective functionalizations at the benzylic position such as deuteration, allylation, and alkylation. (51)

Scheme 40. Photoinduced Synthesis of Tetraboronates and Base-Promoted Site-Selective Functionalization

Finally, the Shi group described that geminal difluoro terminal alkenes are also suitable precursors for the synthesis of racemic polyboronates by means of copper-catalyzed multiboration (Scheme 41). (52) The number of boronates attached to the final product depends on the reaction conditions. Through this method, 1,2-bis(boronates), 1,1,2-tris(boronates), and 1,1,1,2-tetrakis(boronates) are available just by changing the stoichiometry, the copper salt (from Cu(MeCN)PF₆ to CuBrMe₂S), the base (from LiO-t-Bu to LiOMe), and the proton source (from MeOH to HCO₂H). Yields and selectivities range from good to moderate depending on the nature of the starting gem-difluoroalkene. Sequential site-selective functionalizations were also described by this group. In particular, 1,1,1,2-tetraboronates are suitable for building a cyclopentane ring by sequential alkoxide-mediated deborylative alkylation using 1,4-dibromobutane. Suzuki–Miyaura cross coupling is also site selective for 1,1,1,2-tetraboronates and takes place with an in situ deuteration when D₂O is used as a cosolvent.

Scheme 41. Copper-Catalyzed Multiboration of *gem*-Difluoroalkenes and Site-Selective Transformation of 1,1,1,2-Tetrakis(boronates)

4. Conclusions

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Over the last 20 years, 1,2-bis(boronates) have been established as versatile synthetic intermediates for the quick assembly of chiral compounds from a common intermediate. Progress in the catalytic methods available to prepare these vicinal boronates has allowed their use in more complex settings.

Despite the increasing interest in the field, several challenges remain. Most of the examples in the literature describe the selective functionalization of a primary boronic ester versus a secondary one in a Suzuki cross-coupling setting. In this context, palladium catalysis dominates this arena and the use of first-row transition-metal complexes to catalyze these cross-couplings still remains elusive.

Selective mono-oxidations, aminations, halogenations, and homologations are still limited to a few particular examples. In these transformations, the propensity for difunctionalization is still a major challenge to address that would probably require the design of new reagents.

Moreover, selective functionalizations of 1,2-bis(boronates) in which both boryl moieties are attached to a secondary carbon are still rare. In this context, the enantioselective Suzuki cross-coupling of prochiral 1,2-bis(boronates) is still an unmet but highly attractive challenge.

Recently, the visible-light-mediated homolytic cleavage of C–B bonds in 1,2-bis(boronates) has allowed the selective functionalization of a secondary boryl moiety versus a primary one, providing regio- and stereoselectivities which are complementary to those observed through Suzuki cross-coupling. This strategy involves the formation of a carbon-centered radical and opens the door to design future transformations, including the use of combined photoredox/metal catalysis. One of the challenges that this approach will face is the design of enantioselective transformations, since all the stereochemical information is lost after the radical formation. In this context, the use of visible light to promote the selective cleavage of C–B bonds in vicinal C(sp³) poly(boronates) will surely provide new outcomes for the selective functionalization of these molecules.

Overall, the selective functionalization of 1,2-bis(boronates) has provided a powerful tool to prepare highly functionalized compounds with stereocontrol. Their straightfoward preparation from alkenes and alkynes makes them attractive intermediates to quickly build complexity from feedstock materials. The use of 1,2-bis(boronates) in the synthesis of complex molecules shows the high degree of functional group compatibility of the different C–B bond functionalizations. We hope this Perspective will provide inspiration to the creative imagination of synthetic chemists to develop more efficient and general catalytic methods to prepare vicinal bis(boronates) and to find novel applications of these attractive intermediates.

Author Information

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Corresponding Author
- Mariola Tortosa - Departamento de Química Orgánica and Institute for Advanced Research in Chemical Sciences (IAdChem), Universidad Autónoma de Madrid, Madrid 28049, Spain; https://orcid.org/0000-0002-5107-0549; Email: [email protected]
Authors
- Alma Viso - Instituto de Química Orgánica General, IQOG-CSIC, Juan de la Cierva 3, 28006 Madrid, Spain; https://orcid.org/0000-0003-2622-4777
- Roberto Fernández de la Pradilla - Instituto de Química Orgánica General, IQOG-CSIC, Juan de la Cierva 3, 28006 Madrid, Spain
Notes
The authors declare no competing financial interest.

Acknowledgments

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This work was supported by the MICINN (PID2019-107380GB-I00).

References

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Hydroxyl-Directed Cross-Coupling: A Scalable Synthesis of Debromohamigeran E and Other Targets of Interest
Blaisdell, Thomas P.; Morken, James P.
Journal of the American Chemical Society (2015), 137 (27), 8712-8715CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
A hydroxyl functional group positioned β to a pinacol boronate can serve to direct palladium-catalyzed cross-coupling reactions. This feature can be used to control the reaction site in multiply borylated substrates and can activate boronates for reaction that would otherwise be unreactive.
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Blaisdell, T. P.; Caya, T. C.; Zhang, L.; Sanz-Marco, A.; Morken, J. P. Hydroxyl-Directed Stereoselective Diboration of Alkenes. J. Am. Chem. Soc. 2014, 136, 9264– 9267, DOI: 10.1021/ja504228p
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Hydroxyl-Directed Stereoselective Diboration of Alkenes
Blaisdell, Thomas P.; Caya, Thomas C.; Zhang, Liang; Sanz-Marco, Amparo; Morken, James P.
Journal of the American Chemical Society (2014), 136 (26), 9264-9267CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
Acyclic and cyclic homoallylic alcs. such as PhCH2CH(OH)CH2CH:CH2 and I and the bishomoallylic alc. 1-nonen-5-ol underwent diastereoselective diboration with bis(pinacolato)diboron mediated by cesium carbonate in the presence of methanol to give either bis(pinacolboronates) or diols derived from oxidative deborylation such as II and III (BPin = 4,4,5,5-tetramethyl-1,3-dioxa-2-borolane-2-yl) in 51-94% yields and in 2:1->20:1 diastereoselectivities. The method constitutes a formal directed stereoselective dihydroxylation of homoallylic alcs. Diboration of a homoallylic Me ether followed by oxidn. yielded a diol with no diastereoselectivity; competition expts. between a homoallylic alc. and either tetradecene or bishomoallylic alcs. provided the homoallylic alc.-derived diboronates in significantly higher conversions. The base-mediated diborylation was applied to the stereoselective prepn. of a nonracemic C6-C13 fragment of the spongistatins.
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Fang, L.; Yan, L.; Haeffner, F.; Morken, J. P. Carbohydrate-Catalyzed Enantioselective Alkene Diboration: Enhanced Reactivity of 1,2-Bonded Diboron Complexes. J. Am. Chem. Soc. 2016, 138, 2508– 2511, DOI: 10.1021/jacs.5b13174
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Carbohydrate-Catalyzed Enantioselective Alkene Diboration: Enhanced Reactivity of 1,2-Bonded Diboron Complexes
Fang, Lichao; Yan, Lu; Haeffner, Fredrik; Morken, James P.
Journal of the American Chemical Society (2016), 138 (8), 2508-2511CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
Catalytic enantioselective diboration of alkenes is accomplished with readily available carbohydrate-derived catalysts. Mechanistic expts. suggest the intermediacy of 1,2-bonded diboronates.
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Liu, X.; Sun, C.; Mlynarski, S.; Morken, J. P. Synthesis and Stereochemical Assignment of Arenolide. Org. Lett. 2018, 20, 1898– 1901, DOI: 10.1021/acs.orglett.8b00439
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Synthesis and Stereochemical Assignment of Arenolide
Liu, Xun; Sun, Chunrui; Mlynarski, Scott; Morken, James P.
Organic Letters (2018), 20 (7), 1898-1901CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)
The convergent synthesis of candidate stereoisomers of the natural product arenolide was accomplished using recently developed catalytic boron-based reactions. Comparison of the spectral data for candidate structures with that reported for the authentic natural product revealed the likely stereostructure of the natural compd.
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Green, J. C.; Joannou, M. V.; Murray, S. A.; Zanghi, J. M.; Meek, S. J. Enantio- and Diastereoselective Synthesis of Hydroxy Bis(boronates) via Cu-Catalyzed Tandem Borylation/1,2-Addition. ACS Catal. 2017, 7, 4441– 4445, DOI: 10.1021/acscatal.7b01123
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Enantio- and Diastereoselective Synthesis of Hydroxy Bis(boronates) via Cu-Catalyzed Tandem Borylation/1,2-Addition
Green, Jacob C.; Joannou, Matthew V.; Murray, Stephanie A.; Zanghi, Joseph M.; Meek, Simon J.
ACS Catalysis (2017), 7 (7), 4441-4445CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
Catalytic enantioselective synthesis of 1-hydroxy-2,3-bisboronate esters through multicomponent borylation/1,2-addn. is reported. Catalyst and substrates are readily available, form both a C-B and C-C bond, and generate up to three contiguous stereocenters. The reaction is tolerant of aryl, vinyl, and alkyl aldehydes and ketones in up to 95% yield, >20:1 dr, and 99:1 er. Intramol. addns. to aldehydes and ketones result in stereodivergent processes. The hydroxy bis(boronate) ester products are amenable to site-selective chem. elaboration.
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Huang, M.; Hu, J.; Shi, S.; Friedrich, A.; Krebs, J.; Westcott, S. A.; Radius, U.; Marder, T. B. Selective, Transition Metal-free 1,2-Diboration of Alkyl Halides, Tosylates, and Alcohols. Chem. - Eur. J. 2022, 28, e202200480, DOI: 10.1002/chem.202200480
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Selective, Transition Metal-free 1,2-Diboration of Alkyl Halides, Tosylates, and Alcohols
Huang, Mingming; Hu, Jiefeng; Shi, Shasha; Friedrich, Alexandra; Krebs, Johannes; Westcott, Stephen A.; Radius, Udo; Marder, Todd B.
Chemistry - A European Journal (2022), 28 (24), e202200480CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
Defunctionalization of readily available feedstocks to provide alkenes for the synthesis of multifunctional mols. represents an extremely useful process in org. synthesis. Herein, authors describe a transition metal-free, simple and efficient strategy to access alkyl 1,2-bis(boronate esters) via regio- and diastereoselective diboration of secondary and tertiary alkyl halides (Br, Cl, I), tosylates, and alcs. Control expts. demonstrated that the key to this high reactivity and selectivity is the addn. of a combination of potassium iodide and N,N-dimethylacetamide (DMA). The practicality and industrial potential of this transformation are demonstrated by its operational simplicity, wide functional group tolerance, and the late-stage modification of complex mols. From a drug discovery perspective, this synthetic method offers control of the position of diversification and diastereoselectivity in complex ring scaffolds, which would be esp. useful in a lead optimization program.
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Sun, S.-Z.; Talavera, L.; Spieß, P.; Day, C. S.; Martin, R. sp³ Bis-Organometallic Reagents via Catalytic 1,1-Difunctionalization of Unactivated Olefins. Angew. Chem., Int. Ed. 2021, 60, 11740– 11744, DOI: 10.1002/anie.202100810
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sp3 Bis-Organometallic Reagents via Catalytic 1,1-Difunctionalization of Unactivated Olefins
Sun, Shang-Zheng; Talavera, Laura; Spiess, Philipp; Day, Craig S.; Martin, Ruben
Angewandte Chemie, International Edition (2021), 60 (21), 11740-11744CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
A catalytic 1,1-difunctionalization of unactivated olefins en route to sp3 bis-organometallic B,B(Si)-reagents is described. The protocol is characterized by exceptional reaction rates, mild conditions, wide scope, and exquisite selectivity pattern, constituting a new platform to access sp3 bis-organometallics.
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Wu, F.-P.; Luo, X.; Radius, U.; Marder, T. B.; Wu, X.-F. Copper-Catalyzed Synthesis of Stereodefined Cyclopropyl Bis(boronates) from Alkenes with CO as the C1 Source. J. Am. Chem. Soc. 2020, 142, 14074– 14079, DOI: 10.1021/jacs.0c06800
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Copper-Catalyzed Synthesis of Stereodefined Cyclopropyl Bis(boronates) from Alkenes with CO as the C1 Source
Wu, Fu-Peng; Luo, Xiaoling; Radius, Udo; Marder, Todd B.; Wu, Xiao-Feng
Journal of the American Chemical Society (2020), 142 (33), 14074-14079CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
A novel Cu-catalyzed stereodefined procedure for the selective synthesis of cyclopropyl bis(boronates) from terminal alkenes was developed. Various aliph. alkenes were transformed into the desired bis(boronate ester)-substituted cyclopropanes in moderate to good yields. Synthetic transformations of the resulting cyclopropyl bis(boronates) demonstrate their utility. A possible reaction mechanism is proposed.
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Mali, M.; Sharma, G. V. M.; Ghosh, S.; Roisnel, T.; Carboni, B.; Berrée, F. Simmons–Smith Cyclopropanation of Alkenyl 1,2-Bis(boronates): Stereoselective Access to Functionalized Cyclopropyl Derivatives. J. Org. Chem. 2022, 87, 7649– 7657, DOI: 10.1021/acs.joc.2c00152
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Simmons-Smith Cyclopropanation of Alkenyl 1,2-Bis(boronates): Stereoselective Access to Functionalized Cyclopropyl Derivatives
Mali, Maruti; Sharma, Gangavaram V. M.; Ghosh, Subhash; Roisnel, Thierry; Carboni, Bertrand; Berree, Fabienne
Journal of Organic Chemistry (2022), 87 (12), 7649-7657CODEN: JOCEAH; ISSN:0022-3263. (American Chemical Society)
A Simmons-Smith stereodefined procedure for the synthesis of cyclopropyl-1,2-bis(boronates) has been developed starting from the corresponding alkenes. The resulting compds. were then subjected to regioselective Suzuki-Miyaura couplings to produce diversely tri- or tetra-substituted arylcyclopropanes in good yields. Further functionalization with 2-lithiothiophene provided 1,2-bis(aryl)cyclopropanes.
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Novoa, L.; Trulli, L.; Parra, A.; Tortosa, M. Stereoselective Diboration of Spirocyclobutenes: A Platform for the Synthesis of Spirocycles with Orthogonal Exit Vectors. Angew. Chem., Int. Ed. 2021, 60, 11763– 11768, DOI: 10.1002/anie.202101445
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Stereoselective Diboration of Spirocyclobutenes: A Platform for the Synthesis of Spirocycles with Orthogonal Exit Vectors
Novoa, Luis; Trulli, Laura; Parra, Alejandro; Tortosa, Mariola
Angewandte Chemie, International Edition (2021), 60 (21), 11763-11768CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
The diastereo- and enantioselective diboration of spirocyclobutenes provides a platform for the rapid prepn. of a wide variety of chiral spirocyclic building blocks. The chemoselective functionalization of the carbon-boron bond in the products, including a stereospecific sp3-sp2 Suzuki-Miyaura cross-coupling reaction, provides a powerful tool to control the directionality and the nature of the exit vectors in the spirocyclic framework.
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Crudden, C. M.; Ziebenhaus, C.; Rygus, J. P. G.; Ghozati, K.; Unsworth, P. J.; Nambo, M.; Voth, S.; Hutchinson, M.; Laberge, V. S.; Maekawa, Y.; Imao, D. Iterative protecting group-free cross-coupling leading to chiral multiply arylated structures. Nat. Commun. 2016, 7, 11065, DOI: 10.1038/ncomms11065
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Iterative protecting group-free cross-coupling leading to chiral multiply arylated structures
Crudden, Cathleen M.; Ziebenhaus, Christopher; Rygus, Jason P. G.; Ghozati, Kazem; Unsworth, Phillip J.; Nambo, Masakazu; Voth, Samantha; Hutchinson, Marieke; Laberge, Veronique S.; Maekawa, Yuuki; Imao, Daisuke
Nature Communications (2016), 7 (), 11065pp.CODEN: NCAOBW; ISSN:2041-1723. (Nature Publishing Group)
A significant advance in the approach of using protecting group chem. to affect iterative coupling, in which multiple functionalized cross-coupling partners could be employed in iterative coupling without the use of protecting groups was presented. To accomplish this, the orthogonal reactivity of different boron substituents towards the boron-to-palladium transmetalation reaction was exploited. The approach was illustrated in the prepn. of chiral enantioenriched compds., which were known to be privileged structures in active pharmaceutical compds.
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Imao, D.; Glasspoole, B. W.; Laberge, V. S.; Crudden, C. M. Cross Coupling Reactions of Chiral Secondary Organoboronic Esters With Retention of Configuration. J. Am. Chem. Soc. 2009, 131, 5024– 5025, DOI: 10.1021/ja8094075
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Cross Coupling Reactions of Chiral Secondary Organoboronic Esters With Retention of Configuration
Imao, Daisuke; Glasspoole, Ben W.; Laberge, Veronique S.; Crudden, Cathleen M.
Journal of the American Chemical Society (2009), 131 (14), 5024-5025CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
The authors report the 1st example of a coupling reaction of chiral secondary boronic esters generated by the hydroboration of vinyl arenes. In order for the reaction to take place in high yields, the use of Ag oxide as a base and the presence of at least 8 equiv of tri-Ph phosphine per Pd are required. The reaction proceeds with >90% retention of configuration in all cases except one. Remarkably, the linear boronate ester does not react under these conditions.
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Willems, S.; Toupalas, G.; Reisenbauer, J. C.; Morandi, B. A site-selective and stereospecific cascade Suzuki–Miyaura annulation of alkyl 1,2-bisboronic esters and 2,2′-dihalo 1,1′-biaryls. Chem. Commun. 2021, 57, 3909– 3912, DOI: 10.1039/D1CC00648G
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A site-selective and stereospecific cascade Suzuki-Miyaura annulation of alkyl 1,2-bisboronic esters and 2,2'-dihalo 1,1'-biaryls
Willems, Suzanne; Toupalas, Georgios; Reisenbauer, Julia C.; Morandi, Bill
Chemical Communications (Cambridge, United Kingdom) (2021), 57 (32), 3909-3912CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
A cascade Suzuki-Miyaura cross-coupling gave rise to 9,10-dihydrophenanthrenes I [R1 = n-Pr, n-hexyl, (CH2)2Ph, etc.; R2 = H, 3-Me, 2-F, etc.; R3 = H, 6-Me, 7-F, etc.] was developed. Using biaryls with unsym. substitution-pattern full site-selectivity was obsd. Furthermore, this cross-coupling of an alkyl 1,2-bisboronic pinacol ester proceeded through the challenging coupling of a secondary boronate with complete stereoretention.
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Yan, L.; Morken, J. P. Site-Selective Mono-Oxidation of 1,2-Bis(boronates). Org. Lett. 2019, 21, 3760– 3763, DOI: 10.1021/acs.orglett.9b01204
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Site-Selective Mono-Oxidation of 1,2-Bis(boronates)
Yan, Lu; Morken, James P.
Organic Letters (2019), 21 (10), 3760-3763CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)
Site-selective oxidn. of vicinal bis(boronates) is accomplished through the use of trimethylamine N-oxide in 1-butanol solvent. The reaction occurs with good efficiency and selectivity across a range of substrates, providing 2-hydro-1-boronic esters which are versatile intermediates in the synthesis of chiral building blocks.
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Ohtani, T.; Tsuchiya, Y.; Uraguchi, D.; Ooi, T. Photocatalytic borylcyclopropanation of α-borylstyrenes. Org. Chem. Front. 2019, 6, 1734– 1737, DOI: 10.1039/C9QO00197B
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Photocatalytic borylcyclopropanation of α-boryl styrenes
Ohtani, Tsuyoshi; Tsuchiya, Yuto; Uraguchi, Daisuke; Ooi, Takashi
Organic Chemistry Frontiers (2019), 6 (11), 1734-1737CODEN: OCFRA8; ISSN:2052-4129. (Royal Society of Chemistry)
A diastereoselective borylcyclopropanation of α-MIDA-boryl styrenes with 1,1-diiodoborylmethane is developed using 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN) as a catalyst under visible-light irradn. The scope of this photocatalytic method is explored, and the utility of the resulting doubly borylated cyclopropanes is demonstrated by the selective transformation of one of the two boryl groups.
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Lee, H.; Lee, S.; Yun, J. Pd-Catalyzed Stereospecific Cross-Coupling of Chiral α-Borylalkylcopper Species with Aryl Bromides. ACS Catal. 2020, 10, 2069– 2073, DOI: 10.1021/acscatal.9b05213
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Pd-Catalyzed Stereospecific Cross-Coupling of Chiral α-Borylalkylcopper Species with Aryl Bromides
Lee, Hyesu; Lee, Soyeon; Yun, Jaesook
ACS Catalysis (2020), 10 (3), 2069-2073CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
Stereospecific cross-coupling of chiral α-borylalkylcopper species with aryl bromides was achieved using a Pd catalyst. The combination of a Cu catalyst and chiral NHC ligand was efficient for the generation of enantioenriched secondary α-borylorganocopper species via addn. of a Cu-Bpin (= pinacol boronic ester) species to alkenyl boramides. Subsequent stereospecific cross-coupling of such organocopper nucleophiles with aryl bromides successfully proceeded with a Pd-XPhos catalyst. Using 1,2-disubstituted borylalkenes contg. a 1,8-naphthalenediaminatoboryl (Bdan) group produced the corresponding anti-diborylalkanes as a single diastereomer with good enantioselectivity up to 96.5:3.5 er, and subsequent oxidn. generated the corresponding anti-1,2-dihydroxyl compds.
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Xu, P.; Zhang, M.; Ingoglia, B.; Allais, C.; Dechert-Schmitt, A.-M. R.; Singer, R. A.; Morken, J. P. Construction of Azacycles by Intramolecular Amination of Organoboronates and Organobis(boronates). Org. Lett. 2021, 23, 3379– 3383, DOI: 10.1021/acs.orglett.1c00856
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Construction of Azacycles by Intramolecular Amination of Organoboronates and Organobis(boronates)
Xu, Peilin; Zhang, Mingkai; Ingoglia, Bryan; Allais, Christophe; Dechert-Schmitt, Anne-Marie R.; Singer, Robert A.; Morken, James P.
Organic Letters (2021), 23 (9), 3379-3383CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)
Intramol. amination of organoboronates occurs with a 1,2-metalate shift of an aminoboron "ate" complex to form azetidines, pyrrolidines, and piperidines. Bis(boronates) undergo site-selective amination to form boronate-contg. azacycles. Enantiomerically enriched azacycles are formed with high stereospecificity.
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Fawcett, A.; Nitsch, D.; Ali, M.; Bateman, J. M.; Myers, E. L.; Aggarwal, V. K. Regio- and Stereoselective Homologation of 1,2-Bis(Boronic Esters): Stereocontrolled Synthesis of 1,3-Diols and Sch725674. Angew. Chem., Int. Ed. 2016, 55, 14663– 14667, DOI: 10.1002/anie.201608406
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Regio- and Stereoselective Homologation of 1,2-Bis(Boronic Esters): Stereocontrolled Synthesis of 1,3-Diols and Sch 725674
Fawcett, Alexander; Nitsch, Dominik; Ali, Muhammad; Bateman, Joseph M.; Myers, Eddie L.; Aggarwal, Varinder K.
Angewandte Chemie, International Edition (2016), 55 (47), 14663-14667CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
1,2-Bis(boronic esters), derived from the enantioselective diboration of terminal alkenes, can be selectively homologated at the primary boronic ester by using enantioenriched primary/secondary lithiated carbamates or benzoates to give 1,3-bis(boronic esters), which can be subsequently oxidized to the corresponding secondary-secondary and secondary-tertiary 1,3-diols with full stereocontrol. The transformation was applied to a concise total synthesis of the 14-membered macrolactone, Sch 725674. The nine-step synthetic route also features a novel desymmetrizing enantioselective diboration of a divinyl carbinol deriv. and high-yielding late-stage cross-metathesis and Yamaguchi macrolactonization reactions.
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Fiorito, D.; Keskin, S.; Bateman, J. M.; George, M.; Noble, A.; Aggarwal, V. K. Stereocontrolled Total Synthesis of Bastimolide B Using Iterative Homologation of Boronic Esters. J. Am. Chem. Soc. 2022, 144, 7995– 8001, DOI: 10.1021/jacs.2c03192
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Stereocontrolled Total Synthesis of Bastimolide B Using Iterative Homologation of Boronic Esters
Fiorito, Daniele; Keskin, Selbi; Bateman, Joseph M.; George, Malcolm; Noble, Adam; Aggarwal, Varinder K.
Journal of the American Chemical Society (2022), 144 (18), 7995-8001CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
Bastimolide B (I) is a polyhydroxy macrolide isolated from marine cyanobacteria displaying antimalarial activity. It features a dense array of hydroxylated stereogenic centers with 1,5-relationships along a hydrocarbon chain. These 1,5-polyols represent a particularly challenging motif for synthesis, as the remote position of the stereocenters hampers stereocontrol. Herein, we present a strategy for 1,5-polyol stereocontrolled synthesis based on iterative boronic ester homologation with enantiopure magnesium carbenoids. By merging boronic ester homologation and transition-metal-catalyzed alkene hydroboration and diboration, the acyclic backbone of bastimolide B was rapidly assembled from readily available building blocks with full control over the remote stereocenters, enabling the total synthesis to be completed in 16 steps (LLS).
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Takahashi, F.; Nogi, K.; Sasamori, T.; Yorimitsu, H. Diborative Reduction of Alkynes to 1,2-Diboryl-1,2-Dimetalloalkanes: Its Application for the Synthesis of Diverse 1,2-Bis(boronate)s. Org. Lett. 2019, 21, 4739– 4744, DOI: 10.1021/acs.orglett.9b01622
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Diborative Reduction of Alkynes to 1,2-Diboryl-1,2-Dimetalloalkanes: Its Application for the Synthesis of Diverse 1,2-Bis(boronate)s
Takahashi, Fumiya; Nogi, Keisuke; Sasamori, Takahiro; Yorimitsu, Hideki
Organic Letters (2019), 21 (12), 4739-4744CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)
Redn. of alkynes with alkali metals in the presence of B2pin2 results in diboration of alkynes. Distinct from conventional dissolving metal hydrogenations, two C-B bonds and also two C-alkali metal bonds can be constructed in one operation to form 1,2-diboryl-1,2-dimetalloalkanes. The 1,2-diboryl-1,2-dimetalloalkanes generated are readily convertible to a wide range of vicinal bis(boronate)s. In particular, oxidn. of the 1,2-dianionic species provides (E)-1,2-diborylalkenes, unique anti-selective diboration of alkynes being thus executed.
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Kaiser, D.; Noble, A.; Fasano, V.; Aggarwal, V. K. 1,2-Boron Shifts of β-Boryl Radicals Generated from Bis-boronic Esters Using Photoredox Catalysis. J. Am. Chem. Soc. 2019, 141, 14104– 14109, DOI: 10.1021/jacs.9b07564
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1,2-Boron Shifts of β-Boryl Radicals Generated from Bis-boronic Esters Using Photoredox Catalysis
Kaiser, Daniel; Noble, Adam; Fasano, Valerio; Aggarwal, Varinder K.
Journal of the American Chemical Society (2019), 141 (36), 14104-14109CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
1,2-Bis-boronic esters are versatile intermediates that enable the rapid elaboration of simple alkene precursors. Previous reports on their selective mono-functionalization have targeted the most accessible position, retaining the more hindered secondary boronic ester. In contrast, we have found that photoredox-catalyzed mono-deboronation generates primary β-boryl radicals that undergo rapid 1,2-boron shift to form thermodynamically favored secondary radicals, allowing for selective transformation of the more hindered boronic ester. The pivotal 1,2-boron shift, which has been demonstrated to be stereoretentive, enables access to a wide range of functionalized boronic esters and has been applied to highly diastereoselective fragmentation and transannular cyclization reactions. Furthermore, its generality has been shown in a radical cascade reaction with an allylboronic ester.
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Wang, H.; Wu, J.; Noble, A.; Aggarwal, V. K. Selective Coupling of 1,2-Bis-Boronic Esters at the more Substituted Site through Visible-Light Activation of Electron Donor–Acceptor Complexes. Angew. Chem., Int. Ed. 2022, 61, e202202061, DOI: 10.1002/anie.202202061
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Selective Coupling of 1,2-Bis-Boronic Esters at the more Substituted Site through Visible-Light Activation of Electron Donor-Acceptor Complexes
Wang, Hui; Wu, Jingjing; Noble, Adam; Aggarwal, Varinder K.
Angewandte Chemie, International Edition (2022), 61 (18), e202202061CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
1,2-Bis-boronic esters are useful synthetic intermediates particularly as the two boronic esters can be selectively functionalized. Usually, the less hindered primary boronic ester reacts, but herein, we report a coupling reaction that enables the reversal of this selectivity. This is achieved through the formation of a boronate complex with an electron-rich aryllithium which, in the presence of an electron-deficient aryl nitrile, leads to the formation of an electron donor-acceptor complex. Following visible-light photoinduced electron transfer, a primary radical is generated which isomerizes to the more stable secondary radical before radical-radical coupling with the arene radical-anion, giving β-aryl primary boronic ester products. The reactions proceed under catalyst-free conditions. This method also allows stereodivergent coupling of cyclic cis-1,2-bis-boronic esters to provide trans-substituted products, complementing the selectivity obsd. in the Suzuki-Miyaura reaction.
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Wang, H.; Han, W.; Noble, A.; Aggarwal, V. K. Dual Nickel/Photoredox-Catalyzed Site-Selective Cross-Coupling of 1,2-Bis-Boronic Esters Enabled by 1,2-Boron Shifts. Angew. Chem., Int. Ed. 2022, e202207988, DOI: 10.1002/anie.202207988
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Dual Nickel/Photoredox-Catalyzed Site-Selective Cross-Coupling of 1,2-Bis-Boronic Esters Enabled by 1,2-Boron Shifts
Wang, Hui; Han, Wangyujing; Noble, Adam; Aggarwal, Varinder K.
Angewandte Chemie, International Edition (2022), 61 (34), e202207988CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
Site-selective transition-metal-catalyzed mono-deboronative cross-couplings of 1,2-bis-boronic esters are valuable methods for the synthesis of functionalized organoboron compds. However, such cross-couplings are limited to reaction of the sterically less hindered primary boronic ester. Herein, we report a nickel/photoredox-catalyzed mono-deboronative arylation of 1,2-bis-boronic esters that is selective for coupling of the more sterically hindered secondary/tertiary position. This is achieved by taking advantage of a 1,2-boron shift of primary β-boryl radicals to the thermodynamically favored secondary/tertiary radicals, which are subsequently intercepted by the nickel catalyst to enable arylation. The mild conditions are amenable to a broad range of aryl halides to give β-aryl boronic ester products in good yields and with high regioselectivity. This method also allows stereodivergent coupling of cyclic cis-1,2-bis-boronic esters to give trans-substituted products.
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Harada, K.; Nogami, M.; Hirano, K.; Kurauchi, D.; Kato, H.; Miyamoto, K.; Saito, T.; Uchiyama, M. Allylic borylation of tertiary allylic alcohols: a divergent and straightforward access to allylic boronates. Org. Chem. Front. 2016, 3, 565– 569, DOI: 10.1039/C6QO00009F
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Allylic borylation of tertiary allylic alcohols: a divergent and straightforward access to allylic boronates
Harada, Kohei; Nogami, Marina; Hirano, Keiichi; Kurauchi, Daisuke; Kato, Hisano; Miyamoto, Kazunori; Saito, Tatsuo; Uchiyama, Masanobu
Organic Chemistry Frontiers (2016), 3 (5), 565-569CODEN: OCFRA8; ISSN:2052-4129. (Royal Society of Chemistry)
A facile and divergent synthetic process for converting tertiary allylic alcs. to multiply substituted allylic boronates is reported. This methodol. is esp. effective for tertiary alc. substrates, providing the corresponding allylic boronates in moderate to good yields.
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Zanghi, J. M.; Liu, S.; Meek, S. J. Enantio- and Diastereoselective Synthesis of Functionalized Carbocycles by Cu-Catalyzed Borylative Cyclization of Alkynes with Ketones. Org. Lett. 2019, 21, 5172– 5177, DOI: 10.1021/acs.orglett.9b01769
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Enantio- and Diastereoselective Synthesis of Functionalized Carbocycles by Cu-Catalyzed Borylative Cyclization of Alkynes with Ketones
Zanghi, Joseph M.; Liu, Shuang; Meek, Simon J.
Organic Letters (2019), 21 (13), 5172-5177CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)
A single-pot Cu-catalyzed enantio- and diastereoselective tandem hydroboration/borylative cyclization of alkynes with ketones for the synthesis of carbocycles is reported. The reaction proceeds via desymmetrization and generates four contiguous stereocenters, including an all-C quaternary center. The method provides rapid access to [6,5]- and [5,5]-bicycles and cyclopentane products. Catalyst-controlled diastereoselectivity by selection of bisphosphine ligand is noted. Utility of the products is demonstrated by site- and chemoselective transformations that afford valuable alkenyl and allyl organoborons.
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Kliman, L. T.; Mlynarski, S. N.; Ferris, G. E.; Morken, J. P. Catalytic Enantioselective 1,2-Diboration of 1,3-Dienes: Versatile Reagents for Stereoselective Allylation. Angew. Chem., Int. Ed. 2012, 51, 521– 524, DOI: 10.1002/anie.201105716
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Catalytic Enantioselective 1,2-Diboration of 1,3-Dienes: Versatile Reagents for Stereoselective Allylation
Kliman, Laura T.; Mlynarski, Scott N.; Ferris, Grace E.; Morken, James P.
Angewandte Chemie, International Edition (2012), 51 (2), 521-524, S521/1-S521/178CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
A catalytic enantioselective 1,2-diboration of 1,3-dienes has been described. The 1,2-bis(boronate) products can be employed in versatile stereoselective allylation reactions and deliver a range of functionalized chiral building blocks.
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Ferris, G. E.; Hong, K.; Roundtree, I. A.; Morken, J. P. A Catalytic Enantioselective Tandem Allylation Strategy for Rapid Terpene Construction: Application to the Synthesis of Pumilaside Aglycon. J. Am. Chem. Soc. 2013, 135, 2501– 2504, DOI: 10.1021/ja400506j
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A Catalytic Enantioselective Tandem Allylation Strategy for Rapid Terpene Construction: Application to the Synthesis of Pumilaside Aglycon
Ferris, Grace E.; Hong, Kai; Roundtree, Ian A.; Morken, James P.
Journal of the American Chemical Society (2013), 135 (7), 2501-2504CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
Catalytic enantioselective 1,2-diboration of 1,3-dienes followed by cascade allylborations with dicarbonyls provides rapid entry into carbocyclic reaction products. The stereochem. course of this reaction was studied along with its application in the synthesis of pumilaside B aglycon (I).
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Liu, J.; Gao, S.; Chen, M. Asymmetric Syntheses of (E)-δ-Hydroxymethyl-anti-homoallylic Alcohols via Highly Enantio- and Stereoselective Aldehyde Allylation with α-Borylmethyl-(E)-crotylboronate. Org. Lett. 2021, 23, 7808– 7813, DOI: 10.1021/acs.orglett.1c02831
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Asymmetric Syntheses of (E)-δ-Hydroxymethyl-anti-homoallylic Alcohols via Highly Enantio- and Stereoselective Aldehyde Allylation with α-Borylmethyl-(E)-crotylboronate
Liu, Jiaming; Gao, Shang; Chen, Ming
Organic Letters (2021), 23 (20), 7808-7813CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)
Highly stereo- and enantioselective synthesis of (E)-δ-hydroxymethyl-anti-homoallylic alcs. (4R,5S,E)-RCH(OH)CH(CH3)CH=CHCH2OH (R = pentyl, 4-bromophenyl, cyclohexyl, 1-benzofuran-2-yl, etc.) was reported. Under the developed conditions, reactions between aldehydes RCHO and chiral nonracemic α-borylmethyl-(E)-crotylboronate CH3CH=CHCH(Bpin)CH2Bpin upon oxidative workup gave δ-hydroxymethyl-anti-homoallylic alcs. with high E-selectivities and enantioselectivities.
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Liu, J.; Gao, S.; Chen, M. Development of α-Borylmethyl-(Z)-crotylboronate Reagent and Enantioselective Syntheses of (E)-δ-Hydroxymethyl-syn-homoallylic Alcohols via Highly Stereoselective Allylboration. Org. Lett. 2021, 23, 9451– 9456, DOI: 10.1021/acs.orglett.1c03628
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Development of α-Borylmethyl-(Z)-crotylboronate Reagent and Enantioselective Syntheses of (E)-δ-Hydroxymethyl-syn-homoallylic Alcohols via Highly Stereoselective Allylboration
Liu, Jiaming; Gao, Shang; Chen, Ming
Organic Letters (2021), 23 (24), 9451-9456CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)
Hereis, the development of α-borylmethyl-(Z)-crotylboronate reagent MeCH:CHCH(Bpin)CH2Bpin and its application in highly stereo- and enantioselective syntheses of (E)-δ-hydroxymethyl-syn-homoallylic alcs., e.g., (4R,5S,E)-RCH(OH)CHMeCH:CHCH2OH (R = i-Bu, 3-MeOC6H4, PhC≡C, benzofuran-2-yl, etc.), are reported. Starting from 1,4-pentadiene, α-borylmethyl-(Z)-crotylboronate was synthesized in two steps with high Z-selectivity and enantioselectivity. Subsequent aldehyde allylboration with this boron reagent gave highly enantioenriched (E)-δ-hydroxymethyl-syn-homoallylic alcs. upon oxidative workup.
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Gao, S.; Duan, M.; Liu, J.; Yu, P.; Houk, K. N.; Chen, M. Stereochemical Control via Chirality Pairing: Stereodivergent Syntheses of Enantioenriched Homoallylic Alcohols. Angew. Chem., Int. Ed. 2021, 60, 24096– 24106, DOI: 10.1002/anie.202107004
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Stereochemical Control via Chirality Pairing: Stereodivergent Syntheses of Enantioenriched Homoallylic Alcohols
Gao, Shang; Duan, Meng; Liu, Jiaming; Yu, Peiyuan; Houk, Kendall N.; Chen, Ming
Angewandte Chemie, International Edition (2021), 60 (45), 24096-24106CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
The development of stereodivergent syntheses of enantioenriched homoallylic alcs. using chiral nonracemic α-CH2Bpin-substituted crotylboronate CH3CH=CHCH(Bpin)CH2(Bpin) was reported. Chiral phosphoric acid (S)-A-catalyzed asym. allyl addn. with the reagent gave Z-anti-homoallylic alcs. (4R,5R,Z)-RCH(OH)CH(CH3)CH=CHCH2OH (I) (R = 3-bromophenyl, cyclohexyl, 1-benzofuran-2-yl, etc.) with excellent enantioselectivities and Z-selectivities. When the enantiomeric acid catalyst (R)-A was utilized, the stereoselectivity was completely reversed and E-anti-homoallylic alcs. (4R,5R,E)-I were obtained with high E-selectivities and excellent enantioselectivities. By pairing the chirality of the boron reagent with the catalyst, two complementary stereoisomers of chiral homoallylic alcs. can be obtained selectively from the same boron reagent. DFT computational studies were conducted to probe the origins of the obsd. stereoselectivity. These reactions generate highly enantioenriched homoallylic alc. products that are valuable for rapid construction of polyketide structural frameworks.
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Gao, S.; Liu, J.; Chen, M. Catalytic asymmetric transformations of racemic α-borylmethyl-(E)-crotylboronate via kinetic resolution or enantioconvergent reaction pathways. Chem. Sci. 2021, 12, 13398– 13403, DOI: 10.1039/D1SC04047B
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Catalytic asymmetric transformations of racemic α-borylmethyl-(E)-crotylboronate via kinetic resolution or enantioconvergent reaction pathways
Gao, Shang; Liu, Jiaming; Chen, Ming
Chemical Science (2021), 12 (40), 13398-13403CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)
Catalytic asym. transformations of racemic α-borylmethyl-(E)-crotylboronate were reported. The Bronsted acid-catalyzed kinetic resoln.-allylboration reaction sequence of the racemic reagent gave (Z)-δ-hydroxymethyl-anti-homoallylic alcs. RCH(OH)CH(Me)CH=CHCH2OH (R = cyclohexyl, iso-Bu, 3-bromophenyl, benzofuran-2-yl, etc.) with high Z-selectivities and enantioselectivities upon oxidative workup. In parallel, enantioconvergent pathways were utilized to synthesize chiral nonracemic 1,5-diols RCH(OH)CH(Me)(CH2)3OH (R = Ph, phenylethyl, 4-ethoxyphenyl, benzofuran-2-yl, etc.) and α,β-unsatd. aldehyde Ph(CH2)2CH(OTES)CH(Me)CH=CHCHO with excellent optical purity.
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Dorn, S. K.; Tharp, A. E.; Brown, M. K. Modular Synthesis of a Versatile Double-Allylation Reagent for Complex Diol Synthesis. Angew. Chem., Int. Ed. 2021, 60, 16027– 16034, DOI: 10.1002/anie.202103435
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Modular Synthesis of a Versatile Double-Allylation Reagent for Complex Diol Synthesis
Dorn, Stanna K.; Tharp, Annika E.; Brown, M. Kevin
Angewandte Chemie, International Edition (2021), 60 (29), 16027-16034CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
Unsym. bis-boronic reagents R1R2C:CH(Bdan)CH(Bpin)R3 were prepd. by stereoselective borylation of danBCH:CHR3 with R1R2C:CHBr/B2pin2 for stereoselective diol synthesis. Double-allylation reagents allow for the construction of highly complex mols. in an expedient fashion. We have developed an efficient, modular, and enantioselective approach towards accessing novel variants of these reagents through Cu/Pd-catalyzed alkenylboration of alkenylboron derivs. Importantly, we demonstrate novel use of an allylBdan reagent directly in a stereocontrolled allylation without initial deprotection to the boronic ester. These allylation products are employed in a second intermol. allylation to access complex diol motifs, which has yet to be shown with these types of double-allylation reagents. Overall, the modularity of this approach and the ease in which complex structural motifs can be accessed in a rapid manner signify the importance and utility of this method.
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Blair, D. J.; Tanini, D.; Bateman, J. M.; Scott, H. K.; Myers, E. L.; Aggarwal, V. K. Selective uni- and bidirectional homologation of diborylmethane. Chem. Sci. 2017, 8, 2898– 2903, DOI: 10.1039/C6SC05338F
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Selective uni- and bidirectional homologation of diborylmethane
Blair, Daniel J.; Tanini, Damiano; Bateman, Joseph M.; Scott, Helen K.; Myers, Eddie L.; Aggarwal, Varinder K.
Chemical Science (2017), 8 (4), 2898-2903CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)
Diborylmethane can be homologated uni- and bidirectionally by using enantiomerically pure lithium-stabilized carbenoids to give 1,2- and 1,3-bis(boronic esters), resp., in good yield and with excellent levels of enantio- and diastereoselectivity. The high sensitivity of the transformation to steric hindrance enables the exclusive operation of either manifold, effected through the judicious choice of the type of carbenoid, which can be a sparteine-ligated or a diamine-free lithiated benzoate/carbamate. The scope of the 1,2-bis(boronic esters) so generated is complementary to that encompassed by the asym. diboration of alkenes, in that primary-secondary and primary-tertiary 1,2-bis(boronic esters) can be prepd. with equally high levels of selectivity and that functional groups, such as terminal alkynes and alkenes, are tolerated. Methods for forming C2-sym. and non-sym. anti and syn 1,3-bis(boronic esters) are also described and represent a powerful route towards 1,3-functionalized synthetic intermediates.
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Zhang, Y.; Zhao, X.; Bi, C.; Lu, W.; Song, M.; Wang, D.; Qing, G. Selective electrocatalytic hydroboration of aryl alkenes. Green Chem. 2021, 23, 1691– 1699, DOI: 10.1039/D0GC03890C
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Selective electrocatalytic hydroboration of aryl alkenes
Zhang, Yahui; Zhao, Xiangyu; Bi, Ce; Lu, Wenqi; Song, Mengyuan; Wang, Dongdong; Qing, Guangyan
Green Chemistry (2021), 23 (4), 1691-1699CODEN: GRCHFJ; ISSN:1463-9262. (Royal Society of Chemistry)
Organoboron compds. are powerful precursors of value-added org. compds. in synthetic chem., and transition metal-catalyzed borylation has always been dominant. To avoid toxic reagents and costs assocd. with metal catalysts, simpler, more economical and effective approaches for delivering organoborons are highly desirable. Here, without the use of any metal catalysts, a CH3CN-involved electrochem. borylation reaction is reported with alkenes and HBpin as substrates. The site-selectivity is realized to achieve mono- or di-functional borylation of an unsatd. bond by regulating the proportion of HBpin. In addn., the success of gram-scale expts. and versatile conversions confirms the potential applications of this strategy in industrial synthesis. The vital auxiliary role of N,N-diisopropylethylamine (DIEA) in the process of acetonitrile electrolysis is disclosed in the mechanism study. The proposed new strategy provides a generic platform for the discovery of addnl. challenging electrochem. systems for hydrogenation reactions.
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Xu, N.; Liang, H.; Morken, J. P. Copper-Catalyzed Stereospecific Transformations of Alkylboronic Esters. J. Am. Chem. Soc. 2022, 144, 11546– 11552, DOI: 10.1021/jacs.2c04037
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Copper-Catalyzed Stereospecific Transformations of Alkylboronic Esters
Xu, Ningxin; Liang, Hao; Morken, James P.
Journal of the American Chemical Society (2022), 144 (26), 11546-11552CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
Cu-catalyzed stereospecific cross-couplings of boronic esters are reported. Boron "ate" complexes derived from pinacol boronic esters and tert-Bu Li undergo stereospecific transmetalation to Cu cyanide, followed by coupling with alkynyl bromides, allyl halides, propargylic halides, β-haloenones, hydroxylamine esters, and acyl chlorides. Through this simple transformation, com. available inexpensive compds. can be employed to convert primary and secondary alkylboronic esters to a wide array of synthetically useful compds.
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Davenport, E.; Fernández, E. Transition-metal-free synthesis of vicinal triborated compounds and selective functionalisation of the internal C–B bond. Chem. Commun. 2018, 54, 10104– 10107, DOI: 10.1039/C8CC06153J
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Transition-metal-free synthesis of vicinal triborated compounds and selective functionalization of the internal C-B bond
Davenport, Elliot; Fernandez, Elena
Chemical Communications (Cambridge, United Kingdom) (2018), 54 (72), 10104-10107CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
1,2,3-Triborated compds. can be prepd. by simple nucleophilic borylation of 1,3-dienes, without the assistance of metal catalysts. Selective functionalization of the internal C-B bond of the 1,2,3-triborated compds., through cross-coupling with aryl iodides, highlights the powerful methodol. toward polyfunctionalization.
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Coombs, J. R.; Zhang, L.; Morken, J. P. Enantiomerically Enriched Tris(boronates): Readily Accessible Conjunctive Reagents for Asymmetric Synthesis. J. Am. Chem. Soc. 2014, 136, 16140– 16143, DOI: 10.1021/ja510081r
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Enantiomerically Enriched Tris(boronates): Readily Accessible Conjunctive Reagents for Asymmetric Synthesis
Coombs, John R.; Zhang, Liang; Morken, James P.
Journal of the American Chemical Society (2014), 136 (46), 16140-16143CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
The catalytic enantioselective diboration of vinyl boronate esters furnishes chiral tris(boronates) in a selective fashion. Subsequent deborylative alkylation occurs in a diastereoselective fashion, both for intermol. and intramol. processes.
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Gao, G.; Yan, J.; Yang, K.; Chen, F.; Song, Q. Base-controlled highly selective synthesis of alkyl 1,2-bis(boronates) or 1,1,2-tris(boronates) from terminal alkynes. Green Chem. 2017, 19, 3997– 4001, DOI: 10.1039/C7GC01161J
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Abstract
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Scheme 1
Scheme 1. Synthetic Potential and Approaches to Prepare 1,2-Bis(boronate) Esters
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Scheme 2
Scheme 2. Single-Pot Asymmetric Diboration/Suzuki Coupling
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Scheme 3
Scheme 3. Pd-Catalyzed One-Pot Diboration/Cross-Coupling of Alkenes
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Scheme 4
Scheme 4. Selective Cross-Coupling of Bis(boronates) Obtained from Alkynes
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Scheme 5
Scheme 5. Tandem Pt-Catalyzed Diboration/Selective Cross-Coupling/Oxidation
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Scheme 6
Scheme 6. Tandem Base-Induced Diboration/Hydroxyl-Directed Cross-Coupling/Oxidation
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Scheme 7
Scheme 7. Tandem Carbohydrate-Catalyzed Diboration/Hydroxyl-Directed Cross-Coupling/Oxidation
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Scheme 8
Scheme 8. Total Synthesis of Arenolide
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Scheme 9
Scheme 9. Cu-Catalyzed Tandem Borylation/C═O Addition and Site-Selective Functionalization
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Scheme 10
Scheme 10. Transition-Metal-Free Diboration of Alkyl Halides and Tosylates with Bis(catecholato)diboron and Site-Selective Transformations of Vicinal Boronates
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Scheme 11
Scheme 11. Sequential Ni-Catalyzed Synthesis of 1,2-Bis(boronates)/Suzuki–Miyaura Cross-Coupling
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Scheme 12
Scheme 12. Site-Selective Cross-Coupling of Cyclopropyl Bis(boronates)
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Scheme 13
Scheme 13. Diboration-Selective Cross-Coupling of Spirocyclobutenes
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Scheme 14
Scheme 14. Chemoselective Cross-Coupling Reaction of Chiral 1,2-Bis(boronic) esters: Application to the Synthesis of CDP 840
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Scheme 15
Scheme 15. Double Suzuki–Miyaura Cross-Coupling of Vicinal Bis(boronic) Esters
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Scheme 16
Scheme 16. Selective Oxidation of 1,2-Bis(boronic) Esters
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Scheme 17
Scheme 17. Selective Oxidation of Pinacol-Boronate Moiety
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Scheme 18
Scheme 18. Enantioselective Addition of LCu-Bpin to Alkenyl Boron: Pd-Catalyzed Cross-Coupling and Selective Transformations of Bpin in the Presence of Bdan
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Scheme 19
Scheme 19. Selective Oxidation and Amination of 1,2-Bis(boronic) Esters
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Scheme 20
Scheme 20. Chemoselective Intramolecular Amination of Vicinal Bis(boronic) Esters
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Scheme 21
Scheme 21. Selective Homologation of 1,2-Bis(boronic) Esters
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Scheme 22
Scheme 22. Diborative Reduction of Alkynes and Selective Boronate Transformations
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Scheme 23
Scheme 23. Selective Functionalization of 1,2-Bis(boronates) Using Photoredox Catalysis
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Scheme 24
Scheme 24. Photocatalyzed Radical-Mediated Monodeboronative Arylation of Secondary Boronates
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Scheme 25
Scheme 25. Synthesis of Allylic Boronates from Tertiary Allylic Alcohols via Base-Mediated Diboration/Boro-Wittig Elimination
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Scheme 26
Scheme 26. Copper-Catalyzed Borylative Desymmetrization/Cyclization for the Synthesis of Bicyclic Hydroxy Bis(boronates) and Elimination Reactions
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Scheme 27
Scheme 27. Stereoselective Allylation of Aldehydes with 3-Ene-1,2-bis(boronates)
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Scheme 28
Scheme 28. Enantioselective Synthesis of Pumilaside Aglycon
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Scheme 29
Scheme 29. Synthesis and Reactivity with Aldehydes of α-Borylmethyl-(E/Z)-crotylboronates
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Scheme 30
Scheme 30. Enantiodivergent Allylation of Aldehydes Using α-Borylmethyl-(E)-crotylboronates
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Scheme 31
Scheme 31. Kinetic Resolution of α-Borylmethyl (E)-crotylboronate
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Scheme 32
Scheme 32. Synthesis and Application of Double-Allylation Reagents for the Synthesis of 1,4-Diols
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Scheme 33
Scheme 33. Homologation of 1,2-Bis(boronic) Esters with Secondary Benzylic Carbamates and Regioselective Protodeboronation
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Scheme 34
Scheme 34. Selective Protodeboronation and Bromination of Cyclopropyl Bis(boronates)
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Scheme 35
Scheme 35. Electrochemical Diboration of Vinyl Naphthalene and Reactivity of Secondary Benzylic Boronate
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Scheme 36
Scheme 36. Regioselective Copper-Catalyzed Protodeboronation
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Scheme 37
Scheme 37. Site-Selective Suzuki–Miyaura Cross-Coupling in 1,2,3-Tris(boronates)
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Scheme 38
Scheme 38. Synthesis of 1,1,2-Tris(boronates) and Regioselective Deborylative Alkylation
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Scheme 39
Scheme 39. Base-Induced Borylation and Protodeboronation
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Scheme 40
Scheme 40. Photoinduced Synthesis of Tetraboronates and Base-Promoted Site-Selective Functionalization
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Scheme 41
Scheme 41. Copper-Catalyzed Multiboration of gem-Difluoroalkenes and Site-Selective Transformation of 1,1,1,2-Tetrakis(boronates)
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References
This article references 52 other publications.
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  https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1MXhsFaisr3K&md5=6f8f025abbcd17509ec2df0176c053cb
10. 10
  Mlynarski, S. N.; Schuster, C. H.; Morken, J. P. Asymmetric synthesis from terminal alkenes by cascades of diboration and cross-coupling. Nature 2014, 505, 386– 390, DOI: 10.1038/nature12781
  10
  Asymmetric synthesis from terminal alkenes by cascades of diboration and cross-coupling
  Mlynarski, Scott N.; Schuster, Christopher H.; Morken, James P.
  Nature (London, United Kingdom) (2014), 505 (7483), 386-390CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group)
  Nonracemic aryl- and alkenyl-substituted secondary alcs. and amines such as Me(CH2)5CH(OH)CH2R [R = Ph, 4-MeOC6H4, 4-F3CC6H4, 1-naphthyl, 2-MeC6H4, 2-furyl, 3-furyl, 3-pyridinyl, (E)-1-dodecenyl, (E)-2-Me-1-octenyl, 1-cyclopenten-1-yl, 1-cyclohexen-1-yl, 2-methyl-1-propenyl, (Z)-1-propenyl, vinyl] were prepd. in 63-97% yields, and either 94:6-99:1 er or in 17:1->20:1 dr (for nonracemic alkenes) by a one-pot sequence of platinum-catalyzed enantioselective diborylation of terminal alkenes such as 1-octene followed by chemoselective and regioselective coupling of the terminal borane with aryl bromides or alkenyl chlorides in the presence of Pd(OAc)2 and the biarylphosphine ligand RuPhos and oxidative cleavage or amination of the secondary alkylboronate. Palladium-catalyzed cross-coupling of 1,2-bis(boronates) was significantly faster than cross-coupling of alkyl monoboronates; the neighboring unreacted boryl moiety accelerated the coupling of the terminal boronate, allowing the regioselective cross-coupling of the in situ-generated 1,2-diboronates. The method was used to prep. Boc-protected amphetamine, pregabalin hydrochloride, the fungicide (S)-fenpropimorph, and a methylenedioxybenzyl-substituted nonracemic γ-lactone lignan precursor. The tandem diboration/cross-coupling reaction provided products in high yield and high selectivity (>95:5 enantiomer ratio), used low loadings (1-2 mol%) of com. available catalysts and reagents, and accommodated a wide variety of substrates; the method may make possible the prepn. of a broad range of alc. and amine synthesis targets, many of which cannot be easily addressed with current technol.
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11. 11
  Blaisdell, T. P.; Morken, J. P. Hydroxyl-Directed Cross-Coupling: A Scalable Synthesis of Debromohamigeran E and Other Targets of Interest. J. Am. Chem. Soc. 2015, 137, 8712– 8715, DOI: 10.1021/jacs.5b05477
  11
  Hydroxyl-Directed Cross-Coupling: A Scalable Synthesis of Debromohamigeran E and Other Targets of Interest
  Blaisdell, Thomas P.; Morken, James P.
  Journal of the American Chemical Society (2015), 137 (27), 8712-8715CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
  A hydroxyl functional group positioned β to a pinacol boronate can serve to direct palladium-catalyzed cross-coupling reactions. This feature can be used to control the reaction site in multiply borylated substrates and can activate boronates for reaction that would otherwise be unreactive.
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12. 12
  Blaisdell, T. P.; Caya, T. C.; Zhang, L.; Sanz-Marco, A.; Morken, J. P. Hydroxyl-Directed Stereoselective Diboration of Alkenes. J. Am. Chem. Soc. 2014, 136, 9264– 9267, DOI: 10.1021/ja504228p
  12
  Hydroxyl-Directed Stereoselective Diboration of Alkenes
  Blaisdell, Thomas P.; Caya, Thomas C.; Zhang, Liang; Sanz-Marco, Amparo; Morken, James P.
  Journal of the American Chemical Society (2014), 136 (26), 9264-9267CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
  Acyclic and cyclic homoallylic alcs. such as PhCH2CH(OH)CH2CH:CH2 and I and the bishomoallylic alc. 1-nonen-5-ol underwent diastereoselective diboration with bis(pinacolato)diboron mediated by cesium carbonate in the presence of methanol to give either bis(pinacolboronates) or diols derived from oxidative deborylation such as II and III (BPin = 4,4,5,5-tetramethyl-1,3-dioxa-2-borolane-2-yl) in 51-94% yields and in 2:1->20:1 diastereoselectivities. The method constitutes a formal directed stereoselective dihydroxylation of homoallylic alcs. Diboration of a homoallylic Me ether followed by oxidn. yielded a diol with no diastereoselectivity; competition expts. between a homoallylic alc. and either tetradecene or bishomoallylic alcs. provided the homoallylic alc.-derived diboronates in significantly higher conversions. The base-mediated diborylation was applied to the stereoselective prepn. of a nonracemic C6-C13 fragment of the spongistatins.
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13. 13
  Fang, L.; Yan, L.; Haeffner, F.; Morken, J. P. Carbohydrate-Catalyzed Enantioselective Alkene Diboration: Enhanced Reactivity of 1,2-Bonded Diboron Complexes. J. Am. Chem. Soc. 2016, 138, 2508– 2511, DOI: 10.1021/jacs.5b13174
  13
  Carbohydrate-Catalyzed Enantioselective Alkene Diboration: Enhanced Reactivity of 1,2-Bonded Diboron Complexes
  Fang, Lichao; Yan, Lu; Haeffner, Fredrik; Morken, James P.
  Journal of the American Chemical Society (2016), 138 (8), 2508-2511CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
  Catalytic enantioselective diboration of alkenes is accomplished with readily available carbohydrate-derived catalysts. Mechanistic expts. suggest the intermediacy of 1,2-bonded diboronates.
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14. 14
  Liu, X.; Sun, C.; Mlynarski, S.; Morken, J. P. Synthesis and Stereochemical Assignment of Arenolide. Org. Lett. 2018, 20, 1898– 1901, DOI: 10.1021/acs.orglett.8b00439
  14
  Synthesis and Stereochemical Assignment of Arenolide
  Liu, Xun; Sun, Chunrui; Mlynarski, Scott; Morken, James P.
  Organic Letters (2018), 20 (7), 1898-1901CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)
  The convergent synthesis of candidate stereoisomers of the natural product arenolide was accomplished using recently developed catalytic boron-based reactions. Comparison of the spectral data for candidate structures with that reported for the authentic natural product revealed the likely stereostructure of the natural compd.
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15. 15
  Green, J. C.; Joannou, M. V.; Murray, S. A.; Zanghi, J. M.; Meek, S. J. Enantio- and Diastereoselective Synthesis of Hydroxy Bis(boronates) via Cu-Catalyzed Tandem Borylation/1,2-Addition. ACS Catal. 2017, 7, 4441– 4445, DOI: 10.1021/acscatal.7b01123
  15
  Enantio- and Diastereoselective Synthesis of Hydroxy Bis(boronates) via Cu-Catalyzed Tandem Borylation/1,2-Addition
  Green, Jacob C.; Joannou, Matthew V.; Murray, Stephanie A.; Zanghi, Joseph M.; Meek, Simon J.
  ACS Catalysis (2017), 7 (7), 4441-4445CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
  Catalytic enantioselective synthesis of 1-hydroxy-2,3-bisboronate esters through multicomponent borylation/1,2-addn. is reported. Catalyst and substrates are readily available, form both a C-B and C-C bond, and generate up to three contiguous stereocenters. The reaction is tolerant of aryl, vinyl, and alkyl aldehydes and ketones in up to 95% yield, >20:1 dr, and 99:1 er. Intramol. addns. to aldehydes and ketones result in stereodivergent processes. The hydroxy bis(boronate) ester products are amenable to site-selective chem. elaboration.
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16. 16
  Huang, M.; Hu, J.; Shi, S.; Friedrich, A.; Krebs, J.; Westcott, S. A.; Radius, U.; Marder, T. B. Selective, Transition Metal-free 1,2-Diboration of Alkyl Halides, Tosylates, and Alcohols. Chem. - Eur. J. 2022, 28, e202200480, DOI: 10.1002/chem.202200480
  16
  Selective, Transition Metal-free 1,2-Diboration of Alkyl Halides, Tosylates, and Alcohols
  Huang, Mingming; Hu, Jiefeng; Shi, Shasha; Friedrich, Alexandra; Krebs, Johannes; Westcott, Stephen A.; Radius, Udo; Marder, Todd B.
  Chemistry - A European Journal (2022), 28 (24), e202200480CODEN: CEUJED; ISSN:0947-6539. (Wiley-VCH Verlag GmbH & Co. KGaA)
  Defunctionalization of readily available feedstocks to provide alkenes for the synthesis of multifunctional mols. represents an extremely useful process in org. synthesis. Herein, authors describe a transition metal-free, simple and efficient strategy to access alkyl 1,2-bis(boronate esters) via regio- and diastereoselective diboration of secondary and tertiary alkyl halides (Br, Cl, I), tosylates, and alcs. Control expts. demonstrated that the key to this high reactivity and selectivity is the addn. of a combination of potassium iodide and N,N-dimethylacetamide (DMA). The practicality and industrial potential of this transformation are demonstrated by its operational simplicity, wide functional group tolerance, and the late-stage modification of complex mols. From a drug discovery perspective, this synthetic method offers control of the position of diversification and diastereoselectivity in complex ring scaffolds, which would be esp. useful in a lead optimization program.
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17. 17
  Sun, S.-Z.; Talavera, L.; Spieß, P.; Day, C. S.; Martin, R. sp³ Bis-Organometallic Reagents via Catalytic 1,1-Difunctionalization of Unactivated Olefins. Angew. Chem., Int. Ed. 2021, 60, 11740– 11744, DOI: 10.1002/anie.202100810
  17
  sp3 Bis-Organometallic Reagents via Catalytic 1,1-Difunctionalization of Unactivated Olefins
  Sun, Shang-Zheng; Talavera, Laura; Spiess, Philipp; Day, Craig S.; Martin, Ruben
  Angewandte Chemie, International Edition (2021), 60 (21), 11740-11744CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
  A catalytic 1,1-difunctionalization of unactivated olefins en route to sp3 bis-organometallic B,B(Si)-reagents is described. The protocol is characterized by exceptional reaction rates, mild conditions, wide scope, and exquisite selectivity pattern, constituting a new platform to access sp3 bis-organometallics.
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18. 18
  Wu, F.-P.; Luo, X.; Radius, U.; Marder, T. B.; Wu, X.-F. Copper-Catalyzed Synthesis of Stereodefined Cyclopropyl Bis(boronates) from Alkenes with CO as the C1 Source. J. Am. Chem. Soc. 2020, 142, 14074– 14079, DOI: 10.1021/jacs.0c06800
  18
  Copper-Catalyzed Synthesis of Stereodefined Cyclopropyl Bis(boronates) from Alkenes with CO as the C1 Source
  Wu, Fu-Peng; Luo, Xiaoling; Radius, Udo; Marder, Todd B.; Wu, Xiao-Feng
  Journal of the American Chemical Society (2020), 142 (33), 14074-14079CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
  A novel Cu-catalyzed stereodefined procedure for the selective synthesis of cyclopropyl bis(boronates) from terminal alkenes was developed. Various aliph. alkenes were transformed into the desired bis(boronate ester)-substituted cyclopropanes in moderate to good yields. Synthetic transformations of the resulting cyclopropyl bis(boronates) demonstrate their utility. A possible reaction mechanism is proposed.
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19. 19
  Mali, M.; Sharma, G. V. M.; Ghosh, S.; Roisnel, T.; Carboni, B.; Berrée, F. Simmons–Smith Cyclopropanation of Alkenyl 1,2-Bis(boronates): Stereoselective Access to Functionalized Cyclopropyl Derivatives. J. Org. Chem. 2022, 87, 7649– 7657, DOI: 10.1021/acs.joc.2c00152
  19
  Simmons-Smith Cyclopropanation of Alkenyl 1,2-Bis(boronates): Stereoselective Access to Functionalized Cyclopropyl Derivatives
  Mali, Maruti; Sharma, Gangavaram V. M.; Ghosh, Subhash; Roisnel, Thierry; Carboni, Bertrand; Berree, Fabienne
  Journal of Organic Chemistry (2022), 87 (12), 7649-7657CODEN: JOCEAH; ISSN:0022-3263. (American Chemical Society)
  A Simmons-Smith stereodefined procedure for the synthesis of cyclopropyl-1,2-bis(boronates) has been developed starting from the corresponding alkenes. The resulting compds. were then subjected to regioselective Suzuki-Miyaura couplings to produce diversely tri- or tetra-substituted arylcyclopropanes in good yields. Further functionalization with 2-lithiothiophene provided 1,2-bis(aryl)cyclopropanes.
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20. 20
  Novoa, L.; Trulli, L.; Parra, A.; Tortosa, M. Stereoselective Diboration of Spirocyclobutenes: A Platform for the Synthesis of Spirocycles with Orthogonal Exit Vectors. Angew. Chem., Int. Ed. 2021, 60, 11763– 11768, DOI: 10.1002/anie.202101445
  20
  Stereoselective Diboration of Spirocyclobutenes: A Platform for the Synthesis of Spirocycles with Orthogonal Exit Vectors
  Novoa, Luis; Trulli, Laura; Parra, Alejandro; Tortosa, Mariola
  Angewandte Chemie, International Edition (2021), 60 (21), 11763-11768CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
  The diastereo- and enantioselective diboration of spirocyclobutenes provides a platform for the rapid prepn. of a wide variety of chiral spirocyclic building blocks. The chemoselective functionalization of the carbon-boron bond in the products, including a stereospecific sp3-sp2 Suzuki-Miyaura cross-coupling reaction, provides a powerful tool to control the directionality and the nature of the exit vectors in the spirocyclic framework.
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21. 21
  Crudden, C. M.; Ziebenhaus, C.; Rygus, J. P. G.; Ghozati, K.; Unsworth, P. J.; Nambo, M.; Voth, S.; Hutchinson, M.; Laberge, V. S.; Maekawa, Y.; Imao, D. Iterative protecting group-free cross-coupling leading to chiral multiply arylated structures. Nat. Commun. 2016, 7, 11065, DOI: 10.1038/ncomms11065
  21
  Iterative protecting group-free cross-coupling leading to chiral multiply arylated structures
  Crudden, Cathleen M.; Ziebenhaus, Christopher; Rygus, Jason P. G.; Ghozati, Kazem; Unsworth, Phillip J.; Nambo, Masakazu; Voth, Samantha; Hutchinson, Marieke; Laberge, Veronique S.; Maekawa, Yuuki; Imao, Daisuke
  Nature Communications (2016), 7 (), 11065pp.CODEN: NCAOBW; ISSN:2041-1723. (Nature Publishing Group)
  A significant advance in the approach of using protecting group chem. to affect iterative coupling, in which multiple functionalized cross-coupling partners could be employed in iterative coupling without the use of protecting groups was presented. To accomplish this, the orthogonal reactivity of different boron substituents towards the boron-to-palladium transmetalation reaction was exploited. The approach was illustrated in the prepn. of chiral enantioenriched compds., which were known to be privileged structures in active pharmaceutical compds.
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22. 22
  Imao, D.; Glasspoole, B. W.; Laberge, V. S.; Crudden, C. M. Cross Coupling Reactions of Chiral Secondary Organoboronic Esters With Retention of Configuration. J. Am. Chem. Soc. 2009, 131, 5024– 5025, DOI: 10.1021/ja8094075
  22
  Cross Coupling Reactions of Chiral Secondary Organoboronic Esters With Retention of Configuration
  Imao, Daisuke; Glasspoole, Ben W.; Laberge, Veronique S.; Crudden, Cathleen M.
  Journal of the American Chemical Society (2009), 131 (14), 5024-5025CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
  The authors report the 1st example of a coupling reaction of chiral secondary boronic esters generated by the hydroboration of vinyl arenes. In order for the reaction to take place in high yields, the use of Ag oxide as a base and the presence of at least 8 equiv of tri-Ph phosphine per Pd are required. The reaction proceeds with >90% retention of configuration in all cases except one. Remarkably, the linear boronate ester does not react under these conditions.
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23. 23
  Willems, S.; Toupalas, G.; Reisenbauer, J. C.; Morandi, B. A site-selective and stereospecific cascade Suzuki–Miyaura annulation of alkyl 1,2-bisboronic esters and 2,2′-dihalo 1,1′-biaryls. Chem. Commun. 2021, 57, 3909– 3912, DOI: 10.1039/D1CC00648G
  23
  A site-selective and stereospecific cascade Suzuki-Miyaura annulation of alkyl 1,2-bisboronic esters and 2,2'-dihalo 1,1'-biaryls
  Willems, Suzanne; Toupalas, Georgios; Reisenbauer, Julia C.; Morandi, Bill
  Chemical Communications (Cambridge, United Kingdom) (2021), 57 (32), 3909-3912CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
  A cascade Suzuki-Miyaura cross-coupling gave rise to 9,10-dihydrophenanthrenes I [R1 = n-Pr, n-hexyl, (CH2)2Ph, etc.; R2 = H, 3-Me, 2-F, etc.; R3 = H, 6-Me, 7-F, etc.] was developed. Using biaryls with unsym. substitution-pattern full site-selectivity was obsd. Furthermore, this cross-coupling of an alkyl 1,2-bisboronic pinacol ester proceeded through the challenging coupling of a secondary boronate with complete stereoretention.
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24. 24
  Yan, L.; Morken, J. P. Site-Selective Mono-Oxidation of 1,2-Bis(boronates). Org. Lett. 2019, 21, 3760– 3763, DOI: 10.1021/acs.orglett.9b01204
  24
  Site-Selective Mono-Oxidation of 1,2-Bis(boronates)
  Yan, Lu; Morken, James P.
  Organic Letters (2019), 21 (10), 3760-3763CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)
  Site-selective oxidn. of vicinal bis(boronates) is accomplished through the use of trimethylamine N-oxide in 1-butanol solvent. The reaction occurs with good efficiency and selectivity across a range of substrates, providing 2-hydro-1-boronic esters which are versatile intermediates in the synthesis of chiral building blocks.
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25. 25
  Ohtani, T.; Tsuchiya, Y.; Uraguchi, D.; Ooi, T. Photocatalytic borylcyclopropanation of α-borylstyrenes. Org. Chem. Front. 2019, 6, 1734– 1737, DOI: 10.1039/C9QO00197B
  25
  Photocatalytic borylcyclopropanation of α-boryl styrenes
  Ohtani, Tsuyoshi; Tsuchiya, Yuto; Uraguchi, Daisuke; Ooi, Takashi
  Organic Chemistry Frontiers (2019), 6 (11), 1734-1737CODEN: OCFRA8; ISSN:2052-4129. (Royal Society of Chemistry)
  A diastereoselective borylcyclopropanation of α-MIDA-boryl styrenes with 1,1-diiodoborylmethane is developed using 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN) as a catalyst under visible-light irradn. The scope of this photocatalytic method is explored, and the utility of the resulting doubly borylated cyclopropanes is demonstrated by the selective transformation of one of the two boryl groups.
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26. 26
  Lee, H.; Lee, S.; Yun, J. Pd-Catalyzed Stereospecific Cross-Coupling of Chiral α-Borylalkylcopper Species with Aryl Bromides. ACS Catal. 2020, 10, 2069– 2073, DOI: 10.1021/acscatal.9b05213
  26
  Pd-Catalyzed Stereospecific Cross-Coupling of Chiral α-Borylalkylcopper Species with Aryl Bromides
  Lee, Hyesu; Lee, Soyeon; Yun, Jaesook
  ACS Catalysis (2020), 10 (3), 2069-2073CODEN: ACCACS; ISSN:2155-5435. (American Chemical Society)
  Stereospecific cross-coupling of chiral α-borylalkylcopper species with aryl bromides was achieved using a Pd catalyst. The combination of a Cu catalyst and chiral NHC ligand was efficient for the generation of enantioenriched secondary α-borylorganocopper species via addn. of a Cu-Bpin (= pinacol boronic ester) species to alkenyl boramides. Subsequent stereospecific cross-coupling of such organocopper nucleophiles with aryl bromides successfully proceeded with a Pd-XPhos catalyst. Using 1,2-disubstituted borylalkenes contg. a 1,8-naphthalenediaminatoboryl (Bdan) group produced the corresponding anti-diborylalkanes as a single diastereomer with good enantioselectivity up to 96.5:3.5 er, and subsequent oxidn. generated the corresponding anti-1,2-dihydroxyl compds.
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27. 27
  Xu, P.; Zhang, M.; Ingoglia, B.; Allais, C.; Dechert-Schmitt, A.-M. R.; Singer, R. A.; Morken, J. P. Construction of Azacycles by Intramolecular Amination of Organoboronates and Organobis(boronates). Org. Lett. 2021, 23, 3379– 3383, DOI: 10.1021/acs.orglett.1c00856
  27
  Construction of Azacycles by Intramolecular Amination of Organoboronates and Organobis(boronates)
  Xu, Peilin; Zhang, Mingkai; Ingoglia, Bryan; Allais, Christophe; Dechert-Schmitt, Anne-Marie R.; Singer, Robert A.; Morken, James P.
  Organic Letters (2021), 23 (9), 3379-3383CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)
  Intramol. amination of organoboronates occurs with a 1,2-metalate shift of an aminoboron "ate" complex to form azetidines, pyrrolidines, and piperidines. Bis(boronates) undergo site-selective amination to form boronate-contg. azacycles. Enantiomerically enriched azacycles are formed with high stereospecificity.
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28. 28
  Fawcett, A.; Nitsch, D.; Ali, M.; Bateman, J. M.; Myers, E. L.; Aggarwal, V. K. Regio- and Stereoselective Homologation of 1,2-Bis(Boronic Esters): Stereocontrolled Synthesis of 1,3-Diols and Sch725674. Angew. Chem., Int. Ed. 2016, 55, 14663– 14667, DOI: 10.1002/anie.201608406
  28
  Regio- and Stereoselective Homologation of 1,2-Bis(Boronic Esters): Stereocontrolled Synthesis of 1,3-Diols and Sch 725674
  Fawcett, Alexander; Nitsch, Dominik; Ali, Muhammad; Bateman, Joseph M.; Myers, Eddie L.; Aggarwal, Varinder K.
  Angewandte Chemie, International Edition (2016), 55 (47), 14663-14667CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
  1,2-Bis(boronic esters), derived from the enantioselective diboration of terminal alkenes, can be selectively homologated at the primary boronic ester by using enantioenriched primary/secondary lithiated carbamates or benzoates to give 1,3-bis(boronic esters), which can be subsequently oxidized to the corresponding secondary-secondary and secondary-tertiary 1,3-diols with full stereocontrol. The transformation was applied to a concise total synthesis of the 14-membered macrolactone, Sch 725674. The nine-step synthetic route also features a novel desymmetrizing enantioselective diboration of a divinyl carbinol deriv. and high-yielding late-stage cross-metathesis and Yamaguchi macrolactonization reactions.
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29. 29
  Fiorito, D.; Keskin, S.; Bateman, J. M.; George, M.; Noble, A.; Aggarwal, V. K. Stereocontrolled Total Synthesis of Bastimolide B Using Iterative Homologation of Boronic Esters. J. Am. Chem. Soc. 2022, 144, 7995– 8001, DOI: 10.1021/jacs.2c03192
  29
  Stereocontrolled Total Synthesis of Bastimolide B Using Iterative Homologation of Boronic Esters
  Fiorito, Daniele; Keskin, Selbi; Bateman, Joseph M.; George, Malcolm; Noble, Adam; Aggarwal, Varinder K.
  Journal of the American Chemical Society (2022), 144 (18), 7995-8001CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
  Bastimolide B (I) is a polyhydroxy macrolide isolated from marine cyanobacteria displaying antimalarial activity. It features a dense array of hydroxylated stereogenic centers with 1,5-relationships along a hydrocarbon chain. These 1,5-polyols represent a particularly challenging motif for synthesis, as the remote position of the stereocenters hampers stereocontrol. Herein, we present a strategy for 1,5-polyol stereocontrolled synthesis based on iterative boronic ester homologation with enantiopure magnesium carbenoids. By merging boronic ester homologation and transition-metal-catalyzed alkene hydroboration and diboration, the acyclic backbone of bastimolide B was rapidly assembled from readily available building blocks with full control over the remote stereocenters, enabling the total synthesis to be completed in 16 steps (LLS).
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30. 30
  Takahashi, F.; Nogi, K.; Sasamori, T.; Yorimitsu, H. Diborative Reduction of Alkynes to 1,2-Diboryl-1,2-Dimetalloalkanes: Its Application for the Synthesis of Diverse 1,2-Bis(boronate)s. Org. Lett. 2019, 21, 4739– 4744, DOI: 10.1021/acs.orglett.9b01622
  30
  Diborative Reduction of Alkynes to 1,2-Diboryl-1,2-Dimetalloalkanes: Its Application for the Synthesis of Diverse 1,2-Bis(boronate)s
  Takahashi, Fumiya; Nogi, Keisuke; Sasamori, Takahiro; Yorimitsu, Hideki
  Organic Letters (2019), 21 (12), 4739-4744CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)
  Redn. of alkynes with alkali metals in the presence of B2pin2 results in diboration of alkynes. Distinct from conventional dissolving metal hydrogenations, two C-B bonds and also two C-alkali metal bonds can be constructed in one operation to form 1,2-diboryl-1,2-dimetalloalkanes. The 1,2-diboryl-1,2-dimetalloalkanes generated are readily convertible to a wide range of vicinal bis(boronate)s. In particular, oxidn. of the 1,2-dianionic species provides (E)-1,2-diborylalkenes, unique anti-selective diboration of alkynes being thus executed.
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31. 31
  Kaiser, D.; Noble, A.; Fasano, V.; Aggarwal, V. K. 1,2-Boron Shifts of β-Boryl Radicals Generated from Bis-boronic Esters Using Photoredox Catalysis. J. Am. Chem. Soc. 2019, 141, 14104– 14109, DOI: 10.1021/jacs.9b07564
  31
  1,2-Boron Shifts of β-Boryl Radicals Generated from Bis-boronic Esters Using Photoredox Catalysis
  Kaiser, Daniel; Noble, Adam; Fasano, Valerio; Aggarwal, Varinder K.
  Journal of the American Chemical Society (2019), 141 (36), 14104-14109CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
  1,2-Bis-boronic esters are versatile intermediates that enable the rapid elaboration of simple alkene precursors. Previous reports on their selective mono-functionalization have targeted the most accessible position, retaining the more hindered secondary boronic ester. In contrast, we have found that photoredox-catalyzed mono-deboronation generates primary β-boryl radicals that undergo rapid 1,2-boron shift to form thermodynamically favored secondary radicals, allowing for selective transformation of the more hindered boronic ester. The pivotal 1,2-boron shift, which has been demonstrated to be stereoretentive, enables access to a wide range of functionalized boronic esters and has been applied to highly diastereoselective fragmentation and transannular cyclization reactions. Furthermore, its generality has been shown in a radical cascade reaction with an allylboronic ester.
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32. 32
  Wang, H.; Wu, J.; Noble, A.; Aggarwal, V. K. Selective Coupling of 1,2-Bis-Boronic Esters at the more Substituted Site through Visible-Light Activation of Electron Donor–Acceptor Complexes. Angew. Chem., Int. Ed. 2022, 61, e202202061, DOI: 10.1002/anie.202202061
  32
  Selective Coupling of 1,2-Bis-Boronic Esters at the more Substituted Site through Visible-Light Activation of Electron Donor-Acceptor Complexes
  Wang, Hui; Wu, Jingjing; Noble, Adam; Aggarwal, Varinder K.
  Angewandte Chemie, International Edition (2022), 61 (18), e202202061CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
  1,2-Bis-boronic esters are useful synthetic intermediates particularly as the two boronic esters can be selectively functionalized. Usually, the less hindered primary boronic ester reacts, but herein, we report a coupling reaction that enables the reversal of this selectivity. This is achieved through the formation of a boronate complex with an electron-rich aryllithium which, in the presence of an electron-deficient aryl nitrile, leads to the formation of an electron donor-acceptor complex. Following visible-light photoinduced electron transfer, a primary radical is generated which isomerizes to the more stable secondary radical before radical-radical coupling with the arene radical-anion, giving β-aryl primary boronic ester products. The reactions proceed under catalyst-free conditions. This method also allows stereodivergent coupling of cyclic cis-1,2-bis-boronic esters to provide trans-substituted products, complementing the selectivity obsd. in the Suzuki-Miyaura reaction.
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33. 33
  Wang, H.; Han, W.; Noble, A.; Aggarwal, V. K. Dual Nickel/Photoredox-Catalyzed Site-Selective Cross-Coupling of 1,2-Bis-Boronic Esters Enabled by 1,2-Boron Shifts. Angew. Chem., Int. Ed. 2022, e202207988, DOI: 10.1002/anie.202207988
  33
  Dual Nickel/Photoredox-Catalyzed Site-Selective Cross-Coupling of 1,2-Bis-Boronic Esters Enabled by 1,2-Boron Shifts
  Wang, Hui; Han, Wangyujing; Noble, Adam; Aggarwal, Varinder K.
  Angewandte Chemie, International Edition (2022), 61 (34), e202207988CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
  Site-selective transition-metal-catalyzed mono-deboronative cross-couplings of 1,2-bis-boronic esters are valuable methods for the synthesis of functionalized organoboron compds. However, such cross-couplings are limited to reaction of the sterically less hindered primary boronic ester. Herein, we report a nickel/photoredox-catalyzed mono-deboronative arylation of 1,2-bis-boronic esters that is selective for coupling of the more sterically hindered secondary/tertiary position. This is achieved by taking advantage of a 1,2-boron shift of primary β-boryl radicals to the thermodynamically favored secondary/tertiary radicals, which are subsequently intercepted by the nickel catalyst to enable arylation. The mild conditions are amenable to a broad range of aryl halides to give β-aryl boronic ester products in good yields and with high regioselectivity. This method also allows stereodivergent coupling of cyclic cis-1,2-bis-boronic esters to give trans-substituted products.
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34. 34
  Harada, K.; Nogami, M.; Hirano, K.; Kurauchi, D.; Kato, H.; Miyamoto, K.; Saito, T.; Uchiyama, M. Allylic borylation of tertiary allylic alcohols: a divergent and straightforward access to allylic boronates. Org. Chem. Front. 2016, 3, 565– 569, DOI: 10.1039/C6QO00009F
  34
  Allylic borylation of tertiary allylic alcohols: a divergent and straightforward access to allylic boronates
  Harada, Kohei; Nogami, Marina; Hirano, Keiichi; Kurauchi, Daisuke; Kato, Hisano; Miyamoto, Kazunori; Saito, Tatsuo; Uchiyama, Masanobu
  Organic Chemistry Frontiers (2016), 3 (5), 565-569CODEN: OCFRA8; ISSN:2052-4129. (Royal Society of Chemistry)
  A facile and divergent synthetic process for converting tertiary allylic alcs. to multiply substituted allylic boronates is reported. This methodol. is esp. effective for tertiary alc. substrates, providing the corresponding allylic boronates in moderate to good yields.
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35. 35
  Zanghi, J. M.; Liu, S.; Meek, S. J. Enantio- and Diastereoselective Synthesis of Functionalized Carbocycles by Cu-Catalyzed Borylative Cyclization of Alkynes with Ketones. Org. Lett. 2019, 21, 5172– 5177, DOI: 10.1021/acs.orglett.9b01769
  35
  Enantio- and Diastereoselective Synthesis of Functionalized Carbocycles by Cu-Catalyzed Borylative Cyclization of Alkynes with Ketones
  Zanghi, Joseph M.; Liu, Shuang; Meek, Simon J.
  Organic Letters (2019), 21 (13), 5172-5177CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)
  A single-pot Cu-catalyzed enantio- and diastereoselective tandem hydroboration/borylative cyclization of alkynes with ketones for the synthesis of carbocycles is reported. The reaction proceeds via desymmetrization and generates four contiguous stereocenters, including an all-C quaternary center. The method provides rapid access to [6,5]- and [5,5]-bicycles and cyclopentane products. Catalyst-controlled diastereoselectivity by selection of bisphosphine ligand is noted. Utility of the products is demonstrated by site- and chemoselective transformations that afford valuable alkenyl and allyl organoborons.
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36. 36
  Kliman, L. T.; Mlynarski, S. N.; Ferris, G. E.; Morken, J. P. Catalytic Enantioselective 1,2-Diboration of 1,3-Dienes: Versatile Reagents for Stereoselective Allylation. Angew. Chem., Int. Ed. 2012, 51, 521– 524, DOI: 10.1002/anie.201105716
  36
  Catalytic Enantioselective 1,2-Diboration of 1,3-Dienes: Versatile Reagents for Stereoselective Allylation
  Kliman, Laura T.; Mlynarski, Scott N.; Ferris, Grace E.; Morken, James P.
  Angewandte Chemie, International Edition (2012), 51 (2), 521-524, S521/1-S521/178CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
  A catalytic enantioselective 1,2-diboration of 1,3-dienes has been described. The 1,2-bis(boronate) products can be employed in versatile stereoselective allylation reactions and deliver a range of functionalized chiral building blocks.
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37. 37
  Ferris, G. E.; Hong, K.; Roundtree, I. A.; Morken, J. P. A Catalytic Enantioselective Tandem Allylation Strategy for Rapid Terpene Construction: Application to the Synthesis of Pumilaside Aglycon. J. Am. Chem. Soc. 2013, 135, 2501– 2504, DOI: 10.1021/ja400506j
  37
  A Catalytic Enantioselective Tandem Allylation Strategy for Rapid Terpene Construction: Application to the Synthesis of Pumilaside Aglycon
  Ferris, Grace E.; Hong, Kai; Roundtree, Ian A.; Morken, James P.
  Journal of the American Chemical Society (2013), 135 (7), 2501-2504CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
  Catalytic enantioselective 1,2-diboration of 1,3-dienes followed by cascade allylborations with dicarbonyls provides rapid entry into carbocyclic reaction products. The stereochem. course of this reaction was studied along with its application in the synthesis of pumilaside B aglycon (I).
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38. 38
  Liu, J.; Gao, S.; Chen, M. Asymmetric Syntheses of (E)-δ-Hydroxymethyl-anti-homoallylic Alcohols via Highly Enantio- and Stereoselective Aldehyde Allylation with α-Borylmethyl-(E)-crotylboronate. Org. Lett. 2021, 23, 7808– 7813, DOI: 10.1021/acs.orglett.1c02831
  38
  Asymmetric Syntheses of (E)-δ-Hydroxymethyl-anti-homoallylic Alcohols via Highly Enantio- and Stereoselective Aldehyde Allylation with α-Borylmethyl-(E)-crotylboronate
  Liu, Jiaming; Gao, Shang; Chen, Ming
  Organic Letters (2021), 23 (20), 7808-7813CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)
  Highly stereo- and enantioselective synthesis of (E)-δ-hydroxymethyl-anti-homoallylic alcs. (4R,5S,E)-RCH(OH)CH(CH3)CH=CHCH2OH (R = pentyl, 4-bromophenyl, cyclohexyl, 1-benzofuran-2-yl, etc.) was reported. Under the developed conditions, reactions between aldehydes RCHO and chiral nonracemic α-borylmethyl-(E)-crotylboronate CH3CH=CHCH(Bpin)CH2Bpin upon oxidative workup gave δ-hydroxymethyl-anti-homoallylic alcs. with high E-selectivities and enantioselectivities.
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39. 39
  Liu, J.; Gao, S.; Chen, M. Development of α-Borylmethyl-(Z)-crotylboronate Reagent and Enantioselective Syntheses of (E)-δ-Hydroxymethyl-syn-homoallylic Alcohols via Highly Stereoselective Allylboration. Org. Lett. 2021, 23, 9451– 9456, DOI: 10.1021/acs.orglett.1c03628
  39
  Development of α-Borylmethyl-(Z)-crotylboronate Reagent and Enantioselective Syntheses of (E)-δ-Hydroxymethyl-syn-homoallylic Alcohols via Highly Stereoselective Allylboration
  Liu, Jiaming; Gao, Shang; Chen, Ming
  Organic Letters (2021), 23 (24), 9451-9456CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)
  Hereis, the development of α-borylmethyl-(Z)-crotylboronate reagent MeCH:CHCH(Bpin)CH2Bpin and its application in highly stereo- and enantioselective syntheses of (E)-δ-hydroxymethyl-syn-homoallylic alcs., e.g., (4R,5S,E)-RCH(OH)CHMeCH:CHCH2OH (R = i-Bu, 3-MeOC6H4, PhC≡C, benzofuran-2-yl, etc.), are reported. Starting from 1,4-pentadiene, α-borylmethyl-(Z)-crotylboronate was synthesized in two steps with high Z-selectivity and enantioselectivity. Subsequent aldehyde allylboration with this boron reagent gave highly enantioenriched (E)-δ-hydroxymethyl-syn-homoallylic alcs. upon oxidative workup.
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40. 40
  Gao, S.; Duan, M.; Liu, J.; Yu, P.; Houk, K. N.; Chen, M. Stereochemical Control via Chirality Pairing: Stereodivergent Syntheses of Enantioenriched Homoallylic Alcohols. Angew. Chem., Int. Ed. 2021, 60, 24096– 24106, DOI: 10.1002/anie.202107004
  40
  Stereochemical Control via Chirality Pairing: Stereodivergent Syntheses of Enantioenriched Homoallylic Alcohols
  Gao, Shang; Duan, Meng; Liu, Jiaming; Yu, Peiyuan; Houk, Kendall N.; Chen, Ming
  Angewandte Chemie, International Edition (2021), 60 (45), 24096-24106CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
  The development of stereodivergent syntheses of enantioenriched homoallylic alcs. using chiral nonracemic α-CH2Bpin-substituted crotylboronate CH3CH=CHCH(Bpin)CH2(Bpin) was reported. Chiral phosphoric acid (S)-A-catalyzed asym. allyl addn. with the reagent gave Z-anti-homoallylic alcs. (4R,5R,Z)-RCH(OH)CH(CH3)CH=CHCH2OH (I) (R = 3-bromophenyl, cyclohexyl, 1-benzofuran-2-yl, etc.) with excellent enantioselectivities and Z-selectivities. When the enantiomeric acid catalyst (R)-A was utilized, the stereoselectivity was completely reversed and E-anti-homoallylic alcs. (4R,5R,E)-I were obtained with high E-selectivities and excellent enantioselectivities. By pairing the chirality of the boron reagent with the catalyst, two complementary stereoisomers of chiral homoallylic alcs. can be obtained selectively from the same boron reagent. DFT computational studies were conducted to probe the origins of the obsd. stereoselectivity. These reactions generate highly enantioenriched homoallylic alc. products that are valuable for rapid construction of polyketide structural frameworks.
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41. 41
  Gao, S.; Liu, J.; Chen, M. Catalytic asymmetric transformations of racemic α-borylmethyl-(E)-crotylboronate via kinetic resolution or enantioconvergent reaction pathways. Chem. Sci. 2021, 12, 13398– 13403, DOI: 10.1039/D1SC04047B
  41
  Catalytic asymmetric transformations of racemic α-borylmethyl-(E)-crotylboronate via kinetic resolution or enantioconvergent reaction pathways
  Gao, Shang; Liu, Jiaming; Chen, Ming
  Chemical Science (2021), 12 (40), 13398-13403CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)
  Catalytic asym. transformations of racemic α-borylmethyl-(E)-crotylboronate were reported. The Bronsted acid-catalyzed kinetic resoln.-allylboration reaction sequence of the racemic reagent gave (Z)-δ-hydroxymethyl-anti-homoallylic alcs. RCH(OH)CH(Me)CH=CHCH2OH (R = cyclohexyl, iso-Bu, 3-bromophenyl, benzofuran-2-yl, etc.) with high Z-selectivities and enantioselectivities upon oxidative workup. In parallel, enantioconvergent pathways were utilized to synthesize chiral nonracemic 1,5-diols RCH(OH)CH(Me)(CH2)3OH (R = Ph, phenylethyl, 4-ethoxyphenyl, benzofuran-2-yl, etc.) and α,β-unsatd. aldehyde Ph(CH2)2CH(OTES)CH(Me)CH=CHCHO with excellent optical purity.
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42. 42
  Dorn, S. K.; Tharp, A. E.; Brown, M. K. Modular Synthesis of a Versatile Double-Allylation Reagent for Complex Diol Synthesis. Angew. Chem., Int. Ed. 2021, 60, 16027– 16034, DOI: 10.1002/anie.202103435
  42
  Modular Synthesis of a Versatile Double-Allylation Reagent for Complex Diol Synthesis
  Dorn, Stanna K.; Tharp, Annika E.; Brown, M. Kevin
  Angewandte Chemie, International Edition (2021), 60 (29), 16027-16034CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
  Unsym. bis-boronic reagents R1R2C:CH(Bdan)CH(Bpin)R3 were prepd. by stereoselective borylation of danBCH:CHR3 with R1R2C:CHBr/B2pin2 for stereoselective diol synthesis. Double-allylation reagents allow for the construction of highly complex mols. in an expedient fashion. We have developed an efficient, modular, and enantioselective approach towards accessing novel variants of these reagents through Cu/Pd-catalyzed alkenylboration of alkenylboron derivs. Importantly, we demonstrate novel use of an allylBdan reagent directly in a stereocontrolled allylation without initial deprotection to the boronic ester. These allylation products are employed in a second intermol. allylation to access complex diol motifs, which has yet to be shown with these types of double-allylation reagents. Overall, the modularity of this approach and the ease in which complex structural motifs can be accessed in a rapid manner signify the importance and utility of this method.
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43. 43
  Blair, D. J.; Tanini, D.; Bateman, J. M.; Scott, H. K.; Myers, E. L.; Aggarwal, V. K. Selective uni- and bidirectional homologation of diborylmethane. Chem. Sci. 2017, 8, 2898– 2903, DOI: 10.1039/C6SC05338F
  43
  Selective uni- and bidirectional homologation of diborylmethane
  Blair, Daniel J.; Tanini, Damiano; Bateman, Joseph M.; Scott, Helen K.; Myers, Eddie L.; Aggarwal, Varinder K.
  Chemical Science (2017), 8 (4), 2898-2903CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)
  Diborylmethane can be homologated uni- and bidirectionally by using enantiomerically pure lithium-stabilized carbenoids to give 1,2- and 1,3-bis(boronic esters), resp., in good yield and with excellent levels of enantio- and diastereoselectivity. The high sensitivity of the transformation to steric hindrance enables the exclusive operation of either manifold, effected through the judicious choice of the type of carbenoid, which can be a sparteine-ligated or a diamine-free lithiated benzoate/carbamate. The scope of the 1,2-bis(boronic esters) so generated is complementary to that encompassed by the asym. diboration of alkenes, in that primary-secondary and primary-tertiary 1,2-bis(boronic esters) can be prepd. with equally high levels of selectivity and that functional groups, such as terminal alkynes and alkenes, are tolerated. Methods for forming C2-sym. and non-sym. anti and syn 1,3-bis(boronic esters) are also described and represent a powerful route towards 1,3-functionalized synthetic intermediates.
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44. 44
  Zhang, Y.; Zhao, X.; Bi, C.; Lu, W.; Song, M.; Wang, D.; Qing, G. Selective electrocatalytic hydroboration of aryl alkenes. Green Chem. 2021, 23, 1691– 1699, DOI: 10.1039/D0GC03890C
  44
  Selective electrocatalytic hydroboration of aryl alkenes
  Zhang, Yahui; Zhao, Xiangyu; Bi, Ce; Lu, Wenqi; Song, Mengyuan; Wang, Dongdong; Qing, Guangyan
  Green Chemistry (2021), 23 (4), 1691-1699CODEN: GRCHFJ; ISSN:1463-9262. (Royal Society of Chemistry)
  Organoboron compds. are powerful precursors of value-added org. compds. in synthetic chem., and transition metal-catalyzed borylation has always been dominant. To avoid toxic reagents and costs assocd. with metal catalysts, simpler, more economical and effective approaches for delivering organoborons are highly desirable. Here, without the use of any metal catalysts, a CH3CN-involved electrochem. borylation reaction is reported with alkenes and HBpin as substrates. The site-selectivity is realized to achieve mono- or di-functional borylation of an unsatd. bond by regulating the proportion of HBpin. In addn., the success of gram-scale expts. and versatile conversions confirms the potential applications of this strategy in industrial synthesis. The vital auxiliary role of N,N-diisopropylethylamine (DIEA) in the process of acetonitrile electrolysis is disclosed in the mechanism study. The proposed new strategy provides a generic platform for the discovery of addnl. challenging electrochem. systems for hydrogenation reactions.
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45. 45
  Xu, N.; Liang, H.; Morken, J. P. Copper-Catalyzed Stereospecific Transformations of Alkylboronic Esters. J. Am. Chem. Soc. 2022, 144, 11546– 11552, DOI: 10.1021/jacs.2c04037
  45
  Copper-Catalyzed Stereospecific Transformations of Alkylboronic Esters
  Xu, Ningxin; Liang, Hao; Morken, James P.
  Journal of the American Chemical Society (2022), 144 (26), 11546-11552CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
  Cu-catalyzed stereospecific cross-couplings of boronic esters are reported. Boron "ate" complexes derived from pinacol boronic esters and tert-Bu Li undergo stereospecific transmetalation to Cu cyanide, followed by coupling with alkynyl bromides, allyl halides, propargylic halides, β-haloenones, hydroxylamine esters, and acyl chlorides. Through this simple transformation, com. available inexpensive compds. can be employed to convert primary and secondary alkylboronic esters to a wide array of synthetically useful compds.
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46. 46
  Davenport, E.; Fernández, E. Transition-metal-free synthesis of vicinal triborated compounds and selective functionalisation of the internal C–B bond. Chem. Commun. 2018, 54, 10104– 10107, DOI: 10.1039/C8CC06153J
  46
  Transition-metal-free synthesis of vicinal triborated compounds and selective functionalization of the internal C-B bond
  Davenport, Elliot; Fernandez, Elena
  Chemical Communications (Cambridge, United Kingdom) (2018), 54 (72), 10104-10107CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
  1,2,3-Triborated compds. can be prepd. by simple nucleophilic borylation of 1,3-dienes, without the assistance of metal catalysts. Selective functionalization of the internal C-B bond of the 1,2,3-triborated compds., through cross-coupling with aryl iodides, highlights the powerful methodol. toward polyfunctionalization.
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47. 47
  Coombs, J. R.; Zhang, L.; Morken, J. P. Enantiomerically Enriched Tris(boronates): Readily Accessible Conjunctive Reagents for Asymmetric Synthesis. J. Am. Chem. Soc. 2014, 136, 16140– 16143, DOI: 10.1021/ja510081r
  47
  Enantiomerically Enriched Tris(boronates): Readily Accessible Conjunctive Reagents for Asymmetric Synthesis
  Coombs, John R.; Zhang, Liang; Morken, James P.
  Journal of the American Chemical Society (2014), 136 (46), 16140-16143CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
  The catalytic enantioselective diboration of vinyl boronate esters furnishes chiral tris(boronates) in a selective fashion. Subsequent deborylative alkylation occurs in a diastereoselective fashion, both for intermol. and intramol. processes.
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48. 48
  Gao, G.; Yan, J.; Yang, K.; Chen, F.; Song, Q. Base-controlled highly selective synthesis of alkyl 1,2-bis(boronates) or 1,1,2-tris(boronates) from terminal alkynes. Green Chem. 2017, 19, 3997– 4001, DOI: 10.1039/C7GC01161J
  48
  Base-controlled highly selective synthesis of alkyl 1,2-bis(boronates) or 1,1,2-tris(boronates) from terminal alkynes
  Gao, Guoliang; Yan, Jianxiang; Yang, Kai; Chen, Fener; Song, Qiuling
  Green Chemistry (2017), 19 (17), 3997-4001CODEN: GRCHFJ; ISSN:1463-9262. (Royal Society of Chemistry)
  Transition-metal-free base-controlled highly regioselective synthesis of alkyl 1,2-bis(boronates) or 1,1,2-tris(boronates) from various terminal alkynes was disclosed. These reactions are efficient, practical and mild with good regioselectivity, excellent functional group tolerance as well as good scalability, which provide general and complementary methods to access multiborylated alkanes from various terminal alkynes.
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49. 49
  Kuang, Z.; Yang, K.; Zhou, Y.; Song, Q. Base-promoted domino-borylation-protodeboronation strategy. Chem. Commun. 2020, 56, 6469– 6479, DOI: 10.1039/D0CC00614A
  49
  Base-promoted domino-borylation-protodeboronation strategy
  Kuang, Zhijie; Yang, Kai; Zhou, Yao; Song, Qiuling
  Chemical Communications (Cambridge, United Kingdom) (2020), 56 (48), 6469-6479CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)
  A review. Since a nucleophilic sp2 boron species can be generated in situ under the combined action of an inorg. base, B2Pin2 and methanol, research on base-promoted nucleophilic borylation of unsatd. compds. has attracted significant attention. A series of multi-borylated compds., such as alkyl 1,2-bis(boronates), gem-diborylalkanes, and 1,1,2-tris(boronates), are constructed based on this strategy. These multi-borylated compds. can in turn undergo selective protodeboronation, creating a variety of useful boron-contg. compds. This Feature article documents the development of base-promoted domino-borylation-protodeboronation (DBP) strategies and their applications in org. synthesis.
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50. 50
  Yang, K.; Song, Q. Transition-metal-free regioselective synthesis of alkylboronates from arylacetylenes and vinyl arenes. Green Chem. 2016, 18, 932– 936, DOI: 10.1039/C5GC02633D
  50
  Transition-metal-free regioselective synthesis of alkylboronates from arylacetylenes and vinyl arenes
  Yang, Kai; Song, Qiuling
  Green Chemistry (2016), 18 (4), 932-936CODEN: GRCHFJ; ISSN:1463-9262. (Royal Society of Chemistry)
  A transition-metal-free synthesis of alkylboronates ArCH2CH2Bpin (HBpin = 4,4,5,5-tetramethyl-1,3,2-dioxaborolane), utilizing arylacetylenes ArC≡CH or vinyl arenes ArCH:CH2 and bis(pinacolato)diboron through tandem borylation and protodeboronation, has been developed. The borylation of arylacetylenes proceeds under Cs2CO3 catalysis in MeCN at 70°, whereas styrenes are hydroborated in dioxane in the presence of 2.5 equiv of Cs2CO3 and 2.5 equiv of MeOH. This reaction is efficient, practical and environmentally benign, leading to anti-Markovnikov products with excellent regioselectivity, broad functional group tolerance and excellent yields in both small and gram scales.
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51. 51
  Yukimori, D.; Nagashima, Y.; Wang, C.; Muranaka, A.; Uchiyama, M. Quadruple Borylation of Terminal Alkynes. J. Am. Chem. Soc. 2019, 141, 9819– 9822, DOI: 10.1021/jacs.9b04665
  51
  Quadruple Borylation of Terminal Alkynes
  Yukimori, Daiki; Nagashima, Yuki; Wang, Chao; Muranaka, Atsuya; Uchiyama, Masanobu
  Journal of the American Chemical Society (2019), 141 (25), 9819-9822CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
  Authors present the first quadruple borylation reaction of terminal alkynes, affording functionalized 1,1,2,2-tetrakis(boronate) derivs. in a chemo-/regioselective manner. The methodol. is operationally simple and a novel B-B bond activation without the need for a transition-metal catalyst.
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52. 52
  Hu, J.; Zhao, Y.; Shi, Z. Highly tunable multi-borylation of gem-difluoroalkenes via copper catalysis. Nat. Catal. 2018, 1, 860– 869, DOI: 10.1038/s41929-018-0147-9
  52
  Highly tunable multi-borylation of gem-difluoroalkenes via copper catalysis
  Hu, Jiefeng; Zhao, Yue; Shi, Zhuangzhi
  Nature Catalysis (2018), 1 (11), 860-869CODEN: NCAACP; ISSN:2520-1158. (Nature Research)
  Multi-borylated compds. are useful starting materials for the construction of complex mols. Although certain classes of multi-borylated compds., such as geminal and 1,2-bis(boronates), can now be accessed selectively by several well-established methods, the synthesis of one class-those contg. more than two boronate substituents-remains a great challenge. Here, Cu catalytic systems were developed for the borylation of gem-difluoroalkenes with B2pin2 via dual C-F bond activation to afford multi-borylate libraries-1,2-alkyldiboronates, 1,1,2-alkyltriboronates and 1,1,1,2-alkyltetraboronates-by slightly tuning the reaction conditions. The advantages of this strategy include not only avoiding the use of different methods and substrates for each type of multi-substituted alkyl boronate, but also the excellent functional group compatibility, readily accessible gem-difluorovinyl group and highly chemoselective process.
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Site-Selective Functionalization of C(sp3) Vicinal Boronic EstersClick to copy article linkArticle link copied!

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1. Introduction and Overview of Diboration Methods

Scheme 1

2. Site-Selective Functionalization of 1,2-Bis(boronates)

2.1. Suzuki–Miyaura Cross-Coupling

Scheme 2

Scheme 3

Scheme 4

Scheme 5

Scheme 6

Scheme 7

Scheme 8

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Scheme 10

Scheme 11

Scheme 12

Scheme 13

Scheme 14

Scheme 15

2.2. Reactions Based on 1,2-Shift of Boronates

Scheme 16

Scheme 17

Scheme 18

Scheme 19

Scheme 20

Scheme 21

Scheme 22

2.3. Selective Homolytic Cleavage of a C–B Bond

Scheme 23

Scheme 24

2.4. Selective Elimination (Boro-Wittig Reaction)

Scheme 25

Scheme 26

2.5. Boronate Allylation of Carbonyl Compounds

Scheme 27

Scheme 28

Scheme 29

Scheme 30

Scheme 31

Scheme 32

2.6. Miscellaneous Selective Transformations of 1,2-Diboronates

Scheme 33

Scheme 34

Scheme 35

Scheme 36

3. Site-Selective Functionalization of Vicinal C(sp3) Poly(boronic) Esters

Scheme 37

Scheme 38

Scheme 39

Scheme 40

Scheme 41

4. Conclusions

Author Information

Acknowledgments

References

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Abstract

Scheme 1

Scheme 2

Scheme 3

Scheme 4

Scheme 5

Scheme 6

Scheme 7

Scheme 8

Scheme 9

Site-Selective Functionalization of C(sp³) Vicinal Boronic Esters
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3. Site-Selective Functionalization of Vicinal C(sp³) Poly(boronic) Esters