Stereo- and Enantioselective Syntheses of (Z)-1,3-Butadienyl-2-carbinols via Brønsted Acid CatalysisClick to copy article linkArticle link copied!
- Ming Chen*Ming Chen*E-mail: [email protected]Department of Chemistry, Virginia Tech, Blacksburg, Virginia 24061, United StatesMore by Ming Chen
Abstract
A Brønsted acid-catalyzed enantioselective synthesis of (Z)-1,3-butadienyl-2-carbinols is developed. By employing a chiral phosphoric acid as the catalyst, a variety of 1,3-butadienyl-2-carbinols were obtained in good yields with excellent Z-selectivities and enantiopurities from α-alkyl-substituted homoallenyl boronates.
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The 1,3-butadienyl-2-carbinols with a stereochemically defined 1,2-disubstituted alkene unit and their deoxy-analogs are important building blocks for a variety of natural products that are of great biological importance (Figure 1). (1) Several methods have been developed for stereoselective syntheses of these structural motifs in the context of complex molecule synthesis. (2,3) As shown in Scheme 1, the Nicolaou group utilized a sequential olefination approach to access diene C in the total synthesis of des-epoxy caribenolide I. (2a) Horner–Wadsworth–Emmons olefination of an aldehyde with β-ketophosphonate A was utilized to generate α,β-unsaturated ketone B. Subsequent Wittig olefination to install the methylene group gave diene C. In the total synthesis of pteriatoxin, (2b) Kishi showed that Nozaki–Hiyama–Kishi coupling of vinyl bromide D with the aldehyde furnished a diastereomeric mixture of allylic alcohols E. Acylation of the hydroxyl group of E followed by Pd-mediated elimination afforded diene C. An enyne metathesis approach to diene C was developed by the Trost group in their synthesis of des-epoxy-amphidinolide N. (2c) Enyne metathesis of enantioenriched propargylic ether F with the alkene substrate using Grubbs’ II catalyst formed an E/Z mixture of dienes G. (2d) The mixture equilibrated under the reaction conditions over time to form diene C with a high E-selectivity. The synthesis of racemic (Z)-1,3-butadienyl-2-carbinol K was reported by Diver and co-workers by employing a multistep reaction sequence. (2d) Vinyl bromide H was converted to allylic alcohol I using a Nozaki–Hiyama–Kishi coupling reaction. Alcohol I was transformed into aldehyde J in four steps, which reacted under the Wittig olefination conditions to give racemic diene K. With our research focus in organoboron chemistry, (4) we became interested in whether asymmetric aldehyde addition with homoallenyl boronate could generate enantioenriched 1,3-butadienyl-2-carbinols (bottom panel, Scheme 1). (5) Accordingly, we have developed and describe herein chiral phosphoric-acid-catalyzed enantioselective syntheses of Z-1,3-butadienyl-2-carbinols 2 from homoallenyl boronate 1.
Figure 1
Figure 1. Selected natural products containing the 1,3-butadienyl-2-carbinol motif or the deoxy-analog.
Scheme 1
As shown in Scheme 2, homoallenyl boronates 1 were synthesized from pinanediol boronic esters 5 using the conditions developed by Matteson and co-workers. (6) Treatment of boronic ester 5 at −100 °C with lithiated dichloromethane followed by the addition of a solution of ZnCl2 gave an α-chloroboronate intermediate. Subsequent addition of allenyl Grignard reagents to the α-chloroboronate intermediate generated enantioenriched homoallenyl boronates 1 in 72–89% yield.
Scheme 2
aReaction conditions: boronate 1a (0.12 mmol, 1.2 equiv), benzaldehyde (0.1 mmol, 1.0 equiv), catalyst (5 mol %), 4 Å molecular sieves (50 mg), toluene (0.3 mL), −45 °C.
bThe Z/E ratios were determined by 1H NMR analyses of the crude reaction products.
cYields of isolated products are listed.
dThe enantiomeric excesses were determined by modified Mosher ester analyses.
eThe reaction was conducted at rt.
fThe reaction was conducted in CH2Cl2.
After successful preparation of reagents 1, we chose boronate 1a and benzaldehyde as the model system to study the reactions. As shown in Scheme 2, the reaction of 1a and benzaldehyde in the absence of any catalyst gave a 6:1 mixture of dienols 2a and 3a in a 92% combined yield (entry 1). The enantiomeric purity of major isomer 2a is excellent (95% ee). (7) The results indicate that without any catalyst, the reaction of reagent 1a and benzaldehyde has a 6:1 inherent Z-selectivity. Next we sought to identify suitable conditions to improve the Z-selectivity. It has been shown that addition of a Lewis acid can drastically affect the E/Z selectivities of aldehyde addition with α-substituted allylboronates. (8,9) However, the vast majority of prior studies focused on reactions with pinacol boronates. At the outset of our studies, it is not apparent whether these conditions will be applicable to boronates 1 bearing a pinanediol unit that is considerably larger than pinacol. Indeed, the reaction with BF3·OEt2 as the catalyst, which has been shown to promote highly stereoselective allylation with several α-substituted allylboronates, formed only a 1:1 mixture of 2a and 3a in a combined 69% yield (entry 2). Similar selectivities were observed with either Cu(OTf)2 or Sc(OTf)3 as the catalyst (entries 3 and 4). Brønsted acids, such as chiral phosphoric acids, have been utilized to catalyze aldehyde addition with a variety of unsaturated organoboronates with excellent enantioselectivities. (10−13) More recently, they have also been shown to affect the E/Z selectivity in reactions with α-substituted allylboronates. (14) Because pinanediol is much larger than pinacol, whether these acid catalysts will tolerate the large pinanediol group is the key to controlling the alkene geometry of alcohols 2 and 3. In the event, 5 mol % acid (R)-A was used as the catalyst for the reaction of 1a with benzaldehyde at −45 °C. Gratifyingly, the reaction generated alcohol 2a as the only product (Z:E > 30:1). Alcohol 2a was isolated in 86% yield with 98% ee (entry 5). By contrast, the reaction with enantiomeric acid (S)-A as the catalyst only formed a 1.5:1 mixture of 2a and 3a, slightly favoring Z-isomer 2a. These data indicate that the asymmetric induction from acid catalyst (R)-A is the same as the inherent selectivity of reagent 1a in the reaction with benzaldehyde. The reaction of 1a with acid (R)-A as the catalyst is a matched case, and therefore, alcohol 2a was produced with excellent selectivity. On the other hand, the reaction of 1a with (S)-A as the catalyst is mismatched, as the asymmetric induction from acid catalyst (S)-A is the opposite to the inherent selectivity of reagent 1a. Ultimately, the mismatched reaction led to the formation of a mixture of 2a and 3a with poor selectivity.
With suitable conditions identified, we explored the scope of the reaction. As summarized in Scheme 3, in the presence of 5 mol % acid (R)-A, the reactions worked well with a wide array of aldehydes to generate 1,3-butadienyl-2-carbinols 2 with excellent Z-selectivities and enantiopurities. For example, para-substituted aromatic aldehydes reacted smoothly with 1a to afford products 2b–f in 74–92% yields with 96–99% ee. Aromatic aldehydes with a substituent at the meta- or ortho-position also reacted to form alcohols 2g–j in 74–88% yields with 97–99% ee. The reactions with α,β-unsaturated aldehydes occurred to give products 2k–m in 71–78% yields with 95–99% ee. Aldehydes with a heterocycle, such as benzothiophene or Boc-protected indole, reacted with 1a to generate alcohols 2n–p in 73–91% yields with 94–98% ee. Moreover, reactions with aliphatic aldehydes also worked well, furnishing products 2q–r in 74–77% yield with 94–99% ee. In all cases, Z-isomers were obtained with excellent selectivities (>30:1).
Scheme 3
aReaction conditions: boronate 1a (0.12 mmol, 1.2 equiv), aldehyde (0.1 mmol, 1.0 equiv), phosphoric acid (R)-A (5 mol %), 4 Å molecular sieves (50 mg), toluene (0.3 mL), −45 °C.
bYields of isolated products 2 are listed.
cThe Z/E ratios were determined by 1H NMR analyses of the crude reaction products.
dThe enantiomeric excesses were determined by modified Mosher ester analyses.
To evaluate whether homoallenyl boronates with a substituent other than the methyl group at the α-position could also react with aldehydes to form 1,3-butadienyl-2-carbinols with high Z-selectivities, reactions of reagents 1b–d with several representative aldehydes were conducted. As summarized in Scheme 4, the reactions tolerate several alkyl groups, including ethyl, n-propyl, and i-butyl groups, at the α-position of homoallenyl boronates 1. Several aldehydes participated in the reactions with reagents 1b–d, affording alcohol products 4a–i in 73–94% yield with 97–99% ee. Again, the Z-isomers were obtained with excellent selectivities (>30:1) in all cases.
Scheme 4
aReaction conditions: allylboronate 1a (0.12 mmol, 1.2 equiv), aldehyde (0.1 mmol, 1.0 equiv), phosphoric acid (R)-A (5 mol %), 4 Å molecular sieves (50 mg), toluene (0.3 mL), −45 °C.
bYields of isolated products are listed.
cThe Z/E ratios were determined by 1H NMR analyses of the crude reaction products.
dThe enantiomeric excesses were determined by modified Mosher ester analysis.
The reaction of allylboronate 5 with benzaldehyde formed a 1.5:1 mixture of homoallylic alcohols 6 and 7. The observed 6:1 Z-selectivity in the uncatalyzed reaction with boronate 1a is somewhat unexpected (entry 1, Scheme 2). To establish the origin of such selectivity, we analyzed the transition states of these reactions. As depicted in Scheme 5, in transition state TS-2 that leads to E-isomer 7, the α-methyl group adopts a pseudoequatorial position. Such a spatial arrangement will suffer unfavorable gauche interactions between the methyl group of reagent 5 and the pinanediol group on boron (shown with a red arrow in TS-2). In comparison, in transition state TS-1 that forms Z-isomer 6, the methyl group is oriented in a pseudoaxial position, and A1,3 strain between the methyl group and the vinyl hydrogen is developed. (15) Two competing transition states, TS-1 and TS-2, are similar in energy. Therefore, the reaction forms a mixture of Z and E isomers, 6 and 7, with low selectivity. The energy difference of TS-1 and TS-2 is estimated to be 0.24 kcal/mol at 25 °C. The energy penalty for the A1,3 strain in TS-1 is about 1 kcal/mol. Therefore, the energy penalty for the gauche interactions in TS-2 is estimated to be 1.24 kcal/mol at 25 °C.
Scheme 5
In the uncatalyzed reaction of 1a with benzaldehyde, two competing transition states, TS-3 and TS-4, lead to the formation of Z-isomer 2a and E-isomer 3a, respectively (Scheme 5). Close inspection of transition states TS-4 and TS-2 revealed that similar unfavorable gauche interactions also exist in TS-4. By contrast, the A1,3 strain as in TS-1 is not present in TS-3, owing to the lack of the vinyl hydrogen. Therefore, the energy difference of TS-3 and TS-4 is estimated to be 1.24 kcal/mol at 25 °C due to the gauche interactions in TS-4. The observed 6:1 selectivity of 2a and 3a in the reaction with 1a corresponds to a 1.06 kcal/mol energy difference at 25 °C, which is in good accord with the 1.24 kcal/mol caused by the gauche interactions.
In the chiral phosphoric acid (R)-A-catalyzed reaction of 1a, the asymmetric induction from the catalyst is the same as the inherent selectivity of reagent 1a as in transition state TS-5. The additive effect of these two stereodirecting factors is estimated to be at least 3 kcal/mol at 25 °C. Moreover, the steric interactions between the pinanediol group on boron and the acid catalyst (similar to the pinacol boronate case) further destabilize transition state TS-6 (Scheme 6). Therefore, acid (R)-A-catalyzed reaction of 1a with aldehydes proceeded with the favored transition state TS-5 to give Z-isomers 2 with excellent selectivities.
Scheme 6
In summary, we developed a chiral phosphoric acid (R)-A-catalyzed reaction of homoallenyl boronates with aldehydes. A variety of 1,3-butadienyl-2-carbinols were obtained with excellent Z-selectivities and enantioselectivities. Synthetic applications of the method will be reported in due course.
Data Availability
The data underlying this study are available in the published article and its Supporting Information.
Supporting Information
The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.orglett.4c04663.
Experimental procedures, spectra for all new compounds (PDF)
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Acknowledgments
Financial support provided by the National Science Foundation (CAREER Award CHE-2426500) is gratefully acknowledged.
References
This article references 15 other publications.
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Central to the revised strategy was the use of a Horner-Wadsworth-Emmons olefination between a β-ketophosphonate and an aldehyde to construct the C1-C13 sector common to both amphidinolide N and caribenolide I. Stereoselective alkylation allowed for the rapid assembly of the complete caribenolide I carbon skeleton. Key steps in the completion of the synthesis of des-epoxy-caribenolide I structure I included hydrolysis of a sensitive Me ester using Me3SnOH, followed by regioselective macrolactonization of the resulting diol seco-acid and global deprotection. An analogous sequence of late-stage manoeuvres was used to arrive at the fully deprotected des-epoxy-amphidinolide N framework, obtained as a mixt. of hemiacetal II and its bicyclic acetal. Regio- and diastereoselective epoxidn. of the C6 methylene group in the bicyclic acetal provided access to iso-epoxy-amphidinolide N stereoisomer. Several of the prepd. compds. were tested for cytotoxicity against human tumor cell lines, and none showed activity.(b) Matsuura, F.; Peters, R.; Anada, M.; Harried, S. S.; Hao, J.; Kishi, Y. Unified total synthesis of pteriatoxins and their diastereomers. J. Am. Chem. Soc. 2006, 128, 7463, DOI: 10.1021/ja0618954Google Scholar2bhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28XkslKhsbo%253D&md5=bb303ae03f212261a289efbc59528368Unified Total Synthesis of Pteriatoxins and Their DiastereomersMatsuura, Fumiyoshi; Peters, Rene; Anada, Masahiro; Harried, Scott S.; Hao, Junliang; Kishi, YoshitoJournal of the American Chemical Society (2006), 128 (23), 7463-7465CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)A unified total synthesis is reported to access all of the possible diastereomers of pteriatoxins A-C, with the use of an intramol. Diels-Alder reaction as the key step to form the carbo-macrocyclic core structure. The C34/C35-diol protecting groups were found to have significant effects on both the exo/endo-selectivity and the exo-facial selectivity of the intramol. Diels-Alder process.(c) Trost, B. M.; Bai, W. J.; Stivala, C. E.; Hohn, C.; Poock, C.; Heinrich, M.; Xu, S.; Rey, J. Enantioselective synthesis of des-epoxy-amphidinolide N. J. Am. Chem. Soc. 2018, 140, 17316, DOI: 10.1021/jacs.8b11827Google Scholar2chttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXit1OqsbzK&md5=36bff08be25376d942d4db13375c90fcEnantioselective Synthesis of des-Epoxy-Amphidinolide NTrost, Barry M.; Bai, Wen-Ju; Stivala, Craig E.; Hohn, Christoph; Poock, Caroline; Heinrich, Marc; Xu, Shiyan; Rey, JullienJournal of the American Chemical Society (2018), 140 (49), 17316-17326CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The synthesis of des-epoxy-amphidinolide N (I) was achieved in 22 longest linear and 33 total steps. Three generations of synthetic endeavors are reported herein. During the first generation, our key stitching strategy that highlighted an intramol. Ru-catalyzed alkene-alkyne (Ru AA) coupling and a late-stage epoxidn. proved successful, but the installation of the α,α'-dihydroxyl ketone motif employing a dihydroxylation method was problematic. Our second generation of synthetic efforts addressed the scalability problem of the southern fragment synthesis and significantly improved the efficiency of the atom-economical Ru AA coupling, but suffered from several protecting group-based issues that proved insurmountable. Finally, relying on a judicious protecting group strategy together with concise fragment prepn., des-epoxy-amphidinolide N was achieved in a convergent fashion. Calcns. disclose a hydrogen-bonding bridge within amphidinolide N. Comparisons of 13C NMR chem. shift differences using our synthetic des-epoxy-amphidinolide N suggest that amphidinolide N and carbenolide I are probably identical.(d) Giessert, A. J.; Diver, S. T. Equilibrium control in enyne metathesis: crossover studies and the kinetic reactivity of (E,Z)-1,3-disubstituted-1,3-dienes. J. Org. Chem. 2005, 70, 1046, DOI: 10.1021/jo0482209Google Scholar2dhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXjtFGitw%253D%253D&md5=23084f8a505671055c6498b0293e65f3Equilibrium Control in Enyne Metathesis: Crossover Studies and the Kinetic Reactivity of (E,Z)-1,3-Disubstituted-1,3-DienesGiessert, Anthony J.; Diver, Steven T.Journal of Organic Chemistry (2005), 70 (3), 1046-1049CODEN: JOCEAH; ISSN:0022-3263. (American Chemical Society)The stereoselectivity of diene bond formation in the ruthenium-carbene mediated intermol. enyne metathesis was studied. Initial reaction between an alkyne and 1-hexene gave mixts. of E- and Z-isomers in the newly formed 1,3-diene. However, over time the mixts. equilibrated to form mostly the diene of the E-configuration. To evaluate individual reactivity of the E- and Z-dienes, they were independently synthesized. The E-diene was found to be kinetically-stable under nominal metathesis conditions while the Z-diene isomerized to the E-isomer. The Z-isomeric dienes were found to react with other alkenes to produce a new diene of E-configuration. A secondary metathesis mechanism involving ruthenium alkylidene intermediates was invoked to explain the dynamic stereochem. obsd. in this study.
- 3(a) Trost, B. M.; Papillon, J. P. N. Alkene–Alkyne Coupling as a Linchpin: An efficient and convergent synthesis of amphidinolide P. J. Am. Chem. Soc. 2004, 126, 13618, DOI: 10.1021/ja045449xGoogle Scholar3ahttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXnvFGgsLo%253D&md5=f028ee178eb29b085301f76ce373f87eAlkene-alkyne coupling as a linchpin: an efficient and convergent synthesis of amphidinolide PTrost, Barry M.; Papillon, Julien P. N.Journal of the American Chemical Society (2004), 126 (42), 13618-13619CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)A short and efficient synthesis of the cytotoxic macrolide amphidinolide P is described. A remarkably chemo- and regioselective ruthenium-catalyzed alkene-alkyne coupling allows for a convergent synthesis and demonstrates that both enynes and β-lactones are suitable coupling partners. This work also features a novel strategy for the prepn. of macrolactones via intramol. transesterification of β-lactones. The target structure was prepd. in 15 steps for the longest linear sequence and 10% overall yield, 24 steps total.(b) Zhang, W.; Carter, R. G. Synthetic studies toward amphidinolide B1: Synthesis of the C9–C26 fragment. Org. Lett. 2005, 7, 4209, DOI: 10.1021/ol051544eGoogle Scholar3bhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXot1WjtLk%253D&md5=5db553f2c4ed7efe89ccf998bd6253cfSynthetic Studies toward Amphidinolide B1: Synthesis of the C9-C26 FragmentZhang, Wei; Carter, Rich G.Organic Letters (2005), 7 (19), 4209-4212CODEN: ORLEF7; ISSN:1523-7060. (American Chemical Society)The synthesis of the C9-C26 portion I of amphidinolide B1 is described. A Fleming allylation followed by elimination was employed for the construction of the C13-C15 diene portion. Sharpless asym. dihydroxylation was utilized for regioselective functionalization of a styrene-derived alkene, in the presence of the C13-C15 diene functionality. A highly diastereoselective aldol reaction was developed to establish the C18 stereochem.(c) Va, P.; Roush, W. R. Total synthesis of amphidinolide E. J. Am. Chem. Soc. 2006, 128, 15960, DOI: 10.1021/ja066663jGoogle Scholar3chttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28Xht1Clu7vN&md5=9fa7b9b16db69ff68d937de9c1975791Total Synthesis of Amphidinolide EVa, Porino; Roush, William R.Journal of the American Chemical Society (2006), 128 (50), 15960-15961CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)A convergent and highly stereocontrolled synthesis of amphidinolide E (I) has been accomplished. The synthesis features a highly diastereoselective (>20:1) BF3·Et2O promoted [3+2] annulation reaction between aldehyde II and allylsilane III to afford substituted THF IV.(d) Clark, J. S.; Yang, G.; Osnowski, A. P. Synthesis of the C1–C17 fragment of amphidinolides C, C2, C3, and F. Org. Lett. 2013, 15, 1460, DOI: 10.1021/ol4004838Google Scholar3dhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXksFSrtLw%253D&md5=06f140200f51ad7520929f9f9cf800e2Synthesis of the C-1-C-17 Fragment of Amphidinolides C, C2, C3, and FClark, J. Stephen; Yang, Guang; Osnowski, Andrew P.Organic Letters (2013), 15 (7), 1460-1463CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)The C1-C17 fragment, I, of amphidinolides C, C2, C3, and F has been constructed from a trans-2,5-disubstituted dihydrofuranone II prepd. by diastereoselective rearrangement of a free or metal-bound oxonium ylide generated from a metal carbenoid (no data). The dihydrofuranone was converted into aldehyde III, which corresponds to the C1-C8 framework, and this was coupled to the C9-C17 unit IV by nucleophilic addn. of a vinylic anion.
- 4(a) Wang, M.; Gao, S.; Chen, M. Stereoselective syntheses of (E)-γ′,δ-bisboryl-substituted syn-homoallylic alcohols via chemoselective aldehyde allylboration. Org. Lett. 2019, 21, 2151, DOI: 10.1021/acs.orglett.9b00461Google Scholar4ahttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXks1Chtr8%253D&md5=06739d8fddb925c66b6ddc86ec7ef254Stereoselective Syntheses of (E)-γ',δ-Bisboryl-Substituted syn-Homoallylic Alcohols via Chemoselective Aldehyde AllylborationWang, Mengzhou; Gao, Shang; Chen, MingOrganic Letters (2019), 21 (7), 2151-2155CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)The development of a novel (Z)-α,δ-bisboryl-substituted crotylboron reagent (Z)-pinBCH2CH:CHCH(Bpin)2 (2) is reported. Ni-catalyzed 1,4-diboration of dienylboronate provided the targeted crotylboronate in good yield with high regio- and stereoselectivity. Chemo- and stereoselective addn. of this crotylboron reagent to aldehydes RCHO followed by protection of the resulting secondary hydroxyl group gave TES-protected homoallylic alcs. I bearing an alkyl and a vinyl boronate groups with high stereoselectivities.(b) Gao, S.; Chen, J.; Chen, M. (Z)-α-Boryl-crotylboron reagents via Z-selective alkene isomerization and application to stereoselective syntheses of (E)-δ-boryl-syn-homoallylic alcohols. Chem. Sci. 2019, 10, 3637, DOI: 10.1039/C9SC00226JGoogle Scholar4bhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXlt12htbw%253D&md5=39fd1a0691236ad8e0b211468f38a5c4(Z)-α-Boryl-crotylboron reagents via Z-selective alkene isomerization and application to stereoselective syntheses of (E)-δ-boryl-syn-homoallylic alcoholsGao, Shang; Chen, Jichao; Chen, MingChemical Science (2019), 10 (12), 3637-3642CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)Stereoselective synthesis of (Z)-α-boryl-crotylboronate is developed. Ni-catalyzed Z-selective alkene isomerization of α-boryl substituted homoallylboronate provided the targeted (Z)-crotylboronate with high selectivity. Stereoselective addn. of the novel crotylboron reagent to aldehydes gave (E)-δ-boryl-substituted syn-homoallylic alcs. with excellent diastereoselectivities. The vinyl boronate unit in the products can be directly used for a subsequent C-C bond-forming transformation as illustrated in the synthesis of the C1-7 fragment of the natural products nannocystin A and nannocystin Ax.(c) 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, DOI: 10.1021/acs.orglett.1c03628Google Scholar4chttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXis1eqtLnM&md5=faa1c7c9f2a9033283c14a03e66925a0Development of α-Borylmethyl-(Z)-crotylboronate Reagent and Enantioselective Syntheses of (E)-δ-Hydroxymethyl-syn-homoallylic Alcohols via Highly Stereoselective AllylborationLiu, Jiaming; Gao, Shang; Chen, MingOrganic 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.(d) Chen, J.; Miliordos, E.; Chen, M. Highly diastereo- and enantioselective synthesis of 3,6’-bisboryl-anti-1,2-oxaborinan-3-enes: an entry to enantioenriched homoallylic alcohols with a stereodefined trisubstituted alkene. Angew. Chem., Int. Ed. 2021, 60, 840, DOI: 10.1002/anie.202006420Google Scholar4dhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXitlWnt77P&md5=0b7baa6af0d1c00d3abe69652459fbc7Highly Diastereo- and Enantioselective Synthesis of 3,6'-Bisboryl-anti-1,2-oxaborinan-3-enes: An Entry to Enantioenriched Homoallylic Alcohols with A Stereodefined Trisubstituted AlkeneChen, Jichao; Miliordos, Evangelos; Chen, MingAngewandte Chemie, International Edition (2021), 60 (2), 840-848CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)A Cu-catalyzed regio-, diastereo-, and enantioselective carboboration of 1,1-bisboryl-1,3-butadiene is developed to generate enantioenriched 3,6'-bisboryl-anti-1,2-oxaborinan-3-enes. DFT calcns. indicate that the initial diene 1,2-borocupration forms a 3η-allylic Cu as the most stable intermediate. Subsequent aldehyde addn., however, operates under Curtin-Hammett control via a more reactive α,α-bisboryl tertiary allylcopper species to furnish products with high enantioselectivities. The three boryl groups in the products are properly differentiated and can undergo a variety of chemoselective transformations to produce enantioenriched homoallylic alcs. with a stereodefined trisubstituted alkene.(e) Liu, J.; Gao, S.; Miliordos, E.; Chen, M. Asymmetric syntheses of (Z)- or (E)-β,γ-unsaturated ketones via silane-controlled enantiodivergent catalysis. J. Am. Chem. Soc. 2023, 145, 19542, DOI: 10.1021/jacs.3c02595Google Scholar4ehttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3sXhslKksLzF&md5=286450516bb84a7eefa0aa50d260afadAsymmetric Syntheses of (Z)- or (E)-β,γ-Unsaturated Ketones via Silane-Controlled Enantiodivergent CatalysisLiu, Jiaming; Gao, Shang; Miliordos, Evangelos; Chen, MingJournal of the American Chemical Society (2023), 145 (36), 19542-19553CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Cu-catalyzed highly stereoselective and enantiodivergent synthesis of (Z)- or (E)-β,γ-unsatd. ketones from 1,3-butadienyl silanes were developed. The nature of silyl group of dienes had a significant impact on stereo- and enantioselectivity of reactions. Under developed catalytic systems, reactions of acyl fluorides with phenyldimethylsilyl-substituted 1,3-diene gave (Z)-β,γ-unsatd. ketones bearing an α-tertiary stereogenic center with excellent enantioselectivities and high Z-selectivities, where reactions with triisopropylsilyl-substituted 1,3-butadiene formed (E)-β,γ-unsatd. ketones with high optical purities and excellent E-selectivities. The products generated from reactions contain three functional groups with orthogonal chem. reactivities, which can undergo a variety of transformations to afford synthetically valuable intermediates.(f) Gao, S.; Liu, J.; Troya, D.; Chen, M. Copper-catalyzed asymmetric acylboration of 1,3-butadienylboronate with acyl fluorides. Angew. Chem., Int. Ed. 2023, 62, e202304796 DOI: 10.1002/anie.202304796Google Scholar4fhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3sXhvFehtb3F&md5=80bdb29eef4e2e4a92d5380227860c12Copper-Catalyzed Asymmetric Acylboration of 1,3-Butadienylboronate with Acyl FluoridesGao, Shang; Liu, Jiaming; Troya, Diego; Chen, MingAngewandte Chemie, International Edition (2023), 62 (43), e202304796CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)We report herein a Cu-catalyzed regio-, diastereo- and enantioselective acylboration of 1,3-butadienylboronate with acyl fluorides. Under the developed conditions, the reactions provide (Z)-β,γ-unsatd. ketones bearing an α-tertiary stereocenter with high Z-selectivity and excellent enantioselectivities. While direct access to highly enantioenriched E-isomers was not successful, we showed that such mols. can be synthesized with excellent E-selectivity and optical purities via Pd-catalyzed alkene isomerization from the corresponding Z-isomers. The orthogonal chem. reactivities of the functional groups embedded in the ketone products allow for diverse chemoselective transformations, which provides a valuable platform for further derivatization.
- 5(a) Lachance, H.; Hall, D. G. Allylboration of carbonyl compounds. Org. React. 2009, 73, 1, DOI: 10.1002/0471264180.or073.01Google ScholarThere is no corresponding record for this reference.(b) Yus, M.; González-Gómez, J. C.; Foubelo, F. Catalytic enantioselective allylation of carbonyl compounds and imines. Chem. Rev. 2011, 111, 7774, DOI: 10.1021/cr1004474Google Scholar5bhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhtFygu7zJ&md5=df838d62c3869a07067c7c7890e3193dCatalytic enantioselective allylation of carbonyl compounds and iminesYus, Miguel; Gonzalez-Gomez, Jose C.; Foubelo, FranciscoChemical Reviews (Washington, DC, United States) (2011), 111 (12), 7774-7854CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)A review. Methodologies on the catalytic enantioselective addn. of allylic nucleophiles to carbonyl compds., imines (mostly with N-allyl, -aryl, -benzyl, and -sulfonyl substituents), and imine derivs. (hydrazones) will be considered, paying special attention to the most useful reactions from a synthetic point of view.(c) Yus, M.; González-Gómez, J. C.; Foubelo, F. Diastereoselective allylation of carbonyl compounds and imines: application to the synthesis of natural products. Chem. Rev. 2013, 113, 5595, DOI: 10.1021/cr400008hGoogle Scholar5chttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXltVWkurs%253D&md5=2b7c16be59e534fd93566c2bf96aa6b6Diastereoselective Allylation of Carbonyl Compounds and Imines: Application to the Synthesis of Natural ProductsYus, Miguel; Gonzalez-Gomez, Jose C.; Foubelo, FranciscoChemical Reviews (Washington, DC, United States) (2013), 113 (7), 5595-5698CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)A review. The goal of this review is to highlight diastereoselective allylations involving the use of chiral reagents, emphasizing recent developments of synthetic interest. The review is organized according to the source of stereocontrol. The last section of this review will be dedicated to related propargylation/allenylation processes, and to the application of these methodologies to some selected synthesis of natural products.
- 6(a) Matteson, D. S.; Ray, R. alpha-Chloro boronic esters from homologation of boronic esters. J. Am. Chem. Soc. 1980, 102, 7590, DOI: 10.1021/ja00545a046Google Scholar6ahttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL3MXjtV2nsg%253D%253D&md5=e91984e6c035eeadec90335d4401426cDirected chiral synthesis with pinanediol boronic estersMatteson, Donald S.; Ray, RahulJournal of the American Chemical Society (1980), 102 (25), 7590-1CODEN: JACSAT; ISSN:0002-7863.Homologation of boronic esters of (+)-I with LiCHCl2 gave S-α-chloroalkaneboronic esters with high stereoselectivity. Thus, homologation of II (R = Ph) to S-II (R = PhCHCl) which was treated with MeMgBr to give S-II (R = PhCHMe) which was oxidized to give 93.7% pure S-PhCHMeOH.(b) Matteson, D. S.; Sadhu, K. M.; Peterson, M. L. 99% Chirally selective synthesis via pinanediol boronic esters: insect pheromones, diols, and an amino alcohol. J. Am. Chem. Soc. 1986, 108, 810, DOI: 10.1021/ja00264a039Google Scholar6bhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL28Xht12ltLc%253D&md5=ddd2443cdd77f88e62de82fcd35f26e499% Chirally selective synthesis via pinanediol boronic esters: insect pheromones, diols, and an amino alcoholMatteson, Donald S.; Sadhu, Kizhakethil Mathew; Peterson, Mark L.Journal of the American Chemical Society (1986), 108 (4), 810-19CODEN: JACSAT; ISSN:0002-7863.Chiral selectivities exceed 99% in the homologation of (+)-pinanediol alkylboronates I (R = Bu, CH2CHMe2, CH2Ph) to (1S)-(1-chloroalkyl)boronates II by reaction of I with LiCHCl2 at -100° followed by ZnCl2-catalyzed rearrangement of the resulting borate complexes at 0-25°. Diastereoselectivity falls to 95.7% with I (R = Me). (-)-Pinanediol leads to the 1R-isomers. Nucleophilic displacements on II gave new chiral boronic esters which were homologated further. Compatible substituents include α- or β-benzyloxy, δ- or ε-ethylene ketal, β-tert-butoxycarbonyl, α-azido, and β-hexylthio. Three insect pheromones each contg. two chiral centers were prepd.: (3S,4S)-4-methyl-3-heptanol (elm bark beetle), exo-brevicomin (western pine beetle), and eldanolide (African sugar cane borer). Stereocontrolled syntheses also gave (5S,6S)-5,6-decanediol, (5S,6R,7S)-PhCH2OCHBuCHMeCHBuOH, and (5S,6S)-H2NCHBuCHBuOH.
- 7(a) Dale, J. A.; Mosher, H. S. Nuclear magnetic resonance enantiomer regents. Configurational correlations via nuclear magnetic resonance chemical shifts of diastereomeric mandelate, O-methylmandelate, and.alpha.-methoxy-.alpha.-trifluoromethylphenyl-acetate (MTPA) esters. J. Am. Chem. Soc. 1973, 95, 512, DOI: 10.1021/ja00783a034Google Scholar7ahttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaE3sXotlOjtw%253D%253D&md5=27a7f9c81b89c6b29ffed705dc4f689cNuclear magnetic resonance enantiomer regents. Configurational correlations via nuclear magnetic resonance chemical shifts of diastereomeric mandelate, O-methylmandelate, and α-methoxy-α-trifluoromethylphenylacetate (MTPA) estersDale, James A.; Mosher, Harry S.Journal of the American Chemical Society (1973), 95 (2), 512-19CODEN: JACSAT; ISSN:0002-7863.An empirically derived correlation of configuration and NMR chem. shifts for diastereomeric mandelate, O-methylmandelate and α-methoxy-α-trifluoromethylphenylacetate esters has been developed and rationalized in terms of useful models. These models have been successfully applied to over 40 examples. The correlations involve the relative chem. shifts of the proton resonances from the groups attached to the carbinyl carbon of these diastereomeric esters.(b) Ohtani, I.; Kusumi, T.; Kashman, Y.; Kakisawa, H. High-field FT NMR application of Mosher’s method. The absolute configurations of marine terpenoids. J. Am. Chem. Soc. 1991, 113, 4092, DOI: 10.1021/ja00011a006Google Scholar7bhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK3MXktV2jtL0%253D&md5=5dbc18835b60b35f283c7e04767bf238High-field FT NMR application of Mosher's method. The absolute configurations of marine terpenoidsOhtani, Ikuko; Kusumi, Takenori; Kashman, Yoel; Kakisawa, HiroshiJournal of the American Chemical Society (1991), 113 (11), 4092-6CODEN: JACSAT; ISSN:0002-7863.Mosher's (1H) method to elucidate the abs. configuration of marine secondary alcs. was reexamd. by high-field FT NMR spectroscopy, which enables assignment of most of the protons of complex mols. There is a systematic arrangement of Δδ (δS- δR) values obtained for the (R)- and (S)-MTPA (3,3,3-trifluoro-2-methoxy-2-phenylpropionic acid) esters of (-)-methanol, (-)-borneol, cholesterol, and ergosterol, whose abs. configurations are known. Anal. of the Δδ values of these compds. led to a rule which could predict the abs. configurations of natural products. When this rule was applied to marine terpenoids including cembranolides and xenicanes, their abs. configurations were assigned and a part of the results were confirmed by x-ray analyses. In the case of sipholenol A, which has a sterically hindered OH group, this rule is inapplicable. The problem is overcome by inverting the OH group to a less sterically hindered position; the resulting epimer gives systematically arranged Δδ values, which enabled the elucidation of the abs. configuration. Comparison of the present method with Mosher's 19F method indicates that the latter using 19F NMR lacks reliability, and that the abs. configurations of the natural products in the literature detd. by 19F NMR spectra of MTPA esters should all be reexamd.
- 8(a) Kennedy, J. W. J.; Hall, D. G. Dramatic rate enhancement with preservation of stereospecificity in the first metal-catalyzed additions of allylboronates. J. Am. Chem. Soc. 2002, 124, 11586, DOI: 10.1021/ja027453jGoogle Scholar8ahttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD38Xms12rtbw%253D&md5=b6d86454d242b814b07d1c1478a08ba7Dramatic Rate Enhancement with Preservation of Stereospecificity in the First Metal-Catalyzed Additions of AllylboronatesKennedy, Jason W. J.; Hall, Dennis G.Journal of the American Chemical Society (2002), 124 (39), 11586-11587CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The first example of Lewis acid-catalyzed addn. of allylboronates to aldehydes with preserving the stereochem., obsd. in uncatalyzed allylboration reactions, is reported. Thus, addn. of isomerically pure, tetrasubstituted 2-alkoxycarbonyl allylboronates I (R1 = Et, R2 = Me; R1 = Me, R2 = Bu) to aldehydes R3CHO (R3 = Bu, Me2CHCH2, cyclohexyl, Ph, 3-iodophenyl, C6F5, PhCH2CH2) in the presence of Sc(OTf)3, Cu(OTf)2, or Yb(OTf)3 yielded γ-lactones II in good yields at temps. almost 100° lower than those of the corresponding uncatalyzed reactions. The large rate enhancement over the uncatalyzed reaction provides a highly improved practical approach to access aldol-like adducts with a stereogenic quaternary carbon center. The crucial role of the 2-alkoxycarbonyl group on allylboronates I was demonstrated with control expts. using a model allylboronate lacking such an ester group.(b) Ishiyama, T.; Ahiko, T.; Miyaura, N. Acceleration effect of Lewis acid in allylboration of aldehydes: catalytic, regiospecific, diastereospecific, and enantioselective synthesis of homoallyl alcohols. J. Am. Chem. Soc. 2002, 124, 12414, DOI: 10.1021/ja0210345Google Scholar8bhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD38XntlOrtL4%253D&md5=1bb4a36912a174f88840fc326b579ea2Acceleration Effect of Lewis Acid in Allylboration of Aldehydes: Catalytic, Regiospecific, Diastereospecific, and Enantioselective Synthesis of Homoallyl AlcoholsIshiyama, Tatsuo; Ahiko, Taka-aki; Miyaura, NorioJournal of the American Chemical Society (2002), 124 (42), 12414-12415CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The addn. of pinacol allylboronic esters to arom. and aliph. aldehydes smoothly occurred at -78° in toluene in the presence of a catalytic amt. of AlCl3 or Sc(OTf)3 (10 mol %) to give the corresponding homoallyl alcs. in high yields. The reactions proceeded regio- and diastereospecifically, yielding the isomerically pure syn- and anti-homoallyl alcs. from (Z)- and (E)-allylboronic esters, resp. The protocol was also applied to enantioselective reactions by using a chiral Lewis acid catalyst.
- 9(a) Peng, F.; Hall, D. G. Simple, stable, and versatile double-allylation reagents for the stereoselective preparation of skeletally diverse compounds. J. Am. Chem. Soc. 2007, 129, 3070, DOI: 10.1021/ja068985tGoogle Scholar9ahttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXhvFKqtLc%253D&md5=51fa6e04bf31cbde6eda770540aedc92Simple, Stable, and Versatile Double-Allylation Reagents for the Stereoselective Preparation of Skeletally Diverse CompoundsPeng, Feng; Hall, Dennis G.Journal of the American Chemical Society (2007), 129 (11), 3070-3071CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)A new and efficient class of double-allylation reagents, α-trimethylsilylmethyl allylboronate and the crotylboronates, is reported. These stable bimetallic reagents are prepd. easily in enantiomerically pure form and add under BF3 catalysis onto a wide range of aldehydes to afford a direct access to hydroxyl-functionalized allylic silanes, e.g., I, in very high E/Z selectivity and excellent enantioselectivity (up to 98% ee). The useful hydroxyl-functionalized allylsilane intermediates can be exploited in chemodivergent syntheses of various compd. classes such as acyclic propionate units, polysubstituted furans, vinylcyclopropanes, and larger carbocycles.(b) 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)-crotyl-boronate. Org. Lett. 2021, 23, 7808, DOI: 10.1021/acs.orglett.1c02831Google Scholar9bhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXitFalurjO&md5=fdb7ef86f0e8aee51a6678cf54675bcaAsymmetric Syntheses of (E)-δ-Hydroxymethyl-anti-homoallylic Alcohols via Highly Enantio- and Stereoselective Aldehyde Allylation with α-Borylmethyl-(E)-crotylboronateLiu, Jiaming; Gao, Shang; Chen, MingOrganic 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.(c) Liu, J.; Chen, M. Highly stereoselective syntheses of (E)-δ-boryl-anti-homoallylic alcohols via allylation with α-boryl-(E)-crotylboronate. Chem. Commun. 2021, 57, 10799, DOI: 10.1039/D1CC04058HGoogle Scholar9chttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXitFGhs73I&md5=a37b079f4821d49e55d3acea2b683793Highly stereoselective syntheses of (E)-δ-boryl-anti-homoallylic alcohols via allylation with α-boryl-(E)-crotylboronateLiu, Jiaming; Chen, MingChemical Communications (Cambridge, United Kingdom) (2021), 57 (82), 10799-10802CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)A highly stereoselective synthesis of (E)-δ-boryl-anti-homoallylic alcs. is developed. In the presence of a Lewis acid, aldehyde allylation with α-boryl-(E)-crotylboronate gave δ-boryl-anti-homoallylic alcs. in good yields with excellent E-selectivity. The E-vinylboronate group in the products provides a useful handle for cross-coupling reactions as illustrated in the fragment synthesis of chaxamycins.
- 10(a) Jain, P.; Antilla, J. C. Chiral Brønsted acid-catalyzed allylboration of aldehydes. J. Am. Chem. Soc. 2010, 132, 11884, DOI: 10.1021/ja104956sGoogle Scholar10ahttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXpvVartLs%253D&md5=2e3c86159261a9773246329f11b2197cChiral Bronsted Acid-Catalyzed Allylboration of AldehydesJain, Pankaj; Antilla, Jon C.Journal of the American Chemical Society (2010), 132 (34), 11884-11886CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)A new high-yielding and highly enantioselective chiral Bronsted acid-catalyzed allylboration of aldehydes RCHO (R = Ph, 4-ClC6H4, PhCH2, cyclohexyl, 2-thienyl, 1-naphthyl, etc.) with allyl pinacol boronate is described. The reaction is shown to be highly general, with a broad substrate scope that covers aryl, heteroaryl, α,β-unsatd., and aliph. aldehydes. The reaction conditions are also shown to be effective for the catalytic enantioselective crotylation of aldehydes. The high reactivity of the allylboronate is suggested to be due to protonation of the boronate oxygen by the chiral phosphoric acid catalyst.(b) Miura, T.; Nishida, Y.; Morimoto, M.; Murakami, M. Enantioselective synthesis of anti-homoallylic alcohols from terminal alkynes and aldehydes based on concomitant use of a cationic iridium complex and a chiral phosphoric acid. J. Am. Chem. Soc. 2013, 135, 11497, DOI: 10.1021/ja405790tGoogle Scholar10bhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhtFOltrrK&md5=6ae6cf949e8df4b4f184d819d629d910Enantioselective Synthesis of Anti Homoallylic Alcohols from Terminal Alkynes and Aldehydes Based on Concomitant Use of a Cationic Iridium Complex and a Chiral Phosphoric AcidMiura, Tomoya; Nishida, Yui; Morimoto, Masao; Murakami, MasahiroJournal of the American Chemical Society (2013), 135 (31), 11497-11500CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)We report a highly diastereo- and enantioselective synthesis of anti homoallylic alcs. from terminal alkynes via (E)-1-alkenylboronates based upon two catalytic reactions: a cationic iridium complex-catalyzed olefin transposition of (E)-1-alkenylboronates and a chiral phosphoric acid-catalyzed allylation reaction of aldehydes.(c) Incerti-Pradillos, C. A.; Kabeshov, M. A.; Malkov, A. V. Highly stereoselective synthesis of Z-homoallylic alcohols by kinetic resolution of racemic secondary allyl boronates. Angew. Chem., Int. Ed. 2013, 52, 5338, DOI: 10.1002/anie.201300709Google Scholar10chttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXlslyru7c%253D&md5=fadea68f6a8dbc6cafee8139d5707145Highly Stereoselective Synthesis of Z-Homoallylic Alcohols by Kinetic Resolution of Racemic Secondary Allyl BoronatesIncerti-Pradillos, Celia A.; Kabeshov, Mikhail A.; Malkov, Andrei V.Angewandte Chemie, International Edition (2013), 52 (20), 5338-5341CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)In the presence of the bis(triisopropylphenyl)binaphthylphosphoric acid (R)-TRIP and benzoic acid in toluene, racemic secondary allyl pinacolboronates RCH[B(OCMe2CMe2O)]CH:CH2 (R = Me, n-Pr) underwent enantioselective addn. reactions to aldehydes R1CHO [R1 = Ph, (E)-PhCH:CH, PhCH2CH2, 4-MeOC6H4, 4-FC6H4, 4-ClC6H4, 2-naphthyl, 2-MeC6H4, 2-thienyl, 4-F3CC6H4, cyclohexyl] to give nonracemic (R,Z)-homoallylic alcs. RCH:CHCH2CH(OH)R1 [R = Me, n-Pr; R1 = Ph, (E)-PhCH:CH, PhCH2CH2, 4-MeOC6H4, 4-FC6H4, 4-ClC6H4, 2-naphthyl, 2-MeC6H4, 2-thienyl, 4-F3CC6H4, cyclohexyl] in 70-97% yields, 87-99% ee, and (in all but one case) > 25:1 Z:E stereoselectivity. Models for the transitions states of allylboronate addns. to aldehydes were studied computationally, indicating that increasing the size of the boronate ester substituent should increase the stereoselectivity for the (Z)-homoallylic alc. product.(d) Huang, Y.; Yang, X.; Lv, Z.; Cai, C.; Kai, C.; Pei, Y.; Feng, Y. Asymmetric synthesis of 1,3-butadienyl-2-carbinols by the homoallenylboration of aldehydes with a chiral phosphoric acid catalyst. Angew. Chem., Int. Ed. 2015, 54, 7299, DOI: 10.1002/anie.201501832Google Scholar10dhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXnsFymtb4%253D&md5=59a08e15a47eb04e2062baf0e9577d64Asymmetric Synthesis of 1,3-Butadienyl-2-carbinols by the Homoallenylboration of Aldehydes with a Chiral Phosphoric Acid CatalystHuang, Yiyong; Yang, Xing; Lv, Zongchao; Cai, Chen; Kai, Cheng; Pei, Yong; Feng, YuAngewandte Chemie, International Edition (2015), 54 (25), 7299-7302CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)Asym. C(sp)-C(sp2) bond formation to give enantiomerically enriched 1,3-butadienyl-2-carbinols occurred through a homoallenylboration reaction between a 2,3-dienylboronic ester and aldehydes under the catalysis of a chiral phosphoric acid (CPA). A diverse range of enantiomerically enriched butadiene-substituted secondary alcs. with aryl, heterocyclic, and aliph. substituents were synthesized in very high yield with high enantioselectivity. Preliminary d. functional theory (DFT) calcns. suggest that the reaction proceeds via a cyclic six-membered chairlike transition state with essential hydrogen-bond activation in the allene reagent. The catalytic reaction was amenable to the gram-scale synthesis of a chiral alkyl butadienyl adduct, which was converted into an interesting optically pure compd. bearing a benzo-fused spirocyclic cyclopentenone framework.(e) Gao, S.; Chen, M. Enantioselective syn- and anti-alkoxyallylation of aldehydes via Brønsted acid catalysis. Org. Lett. 2018, 20, 6174, DOI: 10.1021/acs.orglett.8b02653Google Scholar10ehttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhslyjsrfO&md5=5d1a235ebfc1ada813a3ff08d62ad1abEnantioselective syn- and anti-Alkoxyallylation of Aldehydes via Bronsted Acid CatalysisGao, Shang; Chen, MingOrganic Letters (2018), 20 (19), 6174-6177CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)A diastereo- and enantioselective alkoxyallylation via phosphoric acid catalysis was reported. Under the developed conditions, either 1,2-syn- or 1,2-anti-alkoxyallylation adducts were obtained in good yields with high enantioselectivities.(f) Gao, S.; Chen, M. Enantioselective syntheses of 1, 4-pentadien-3-yl carbinols via Brønsted acid catalysis. Org. Lett. 2020, 22, 400, DOI: 10.1021/acs.orglett.9b04089Google Scholar10fhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXisVCht73E&md5=1e532d5a996925a8534ebec8b010ecf2Enantioselective Syntheses of 1,4-Pentadien-3-yl Carbinols via Bronsted Acid CatalysisGao, Shang; Chen, MingOrganic Letters (2020), 22 (2), 400-404CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)An asym. addn. of substituted 1,3-pentadienylboronates to aldehydes via Bronsted acid catalysis is reported. Under the developed conditions, a variety of synthetically useful 1,4-pentadien-3-yl carbinols were obtained in good yields with high enantioselectivities in the presence of a catalytic amt. of a chiral phosphoric acid.(g) Liu, J.; Chen, M. Enantioselective anti- and syn-(borylmethyl)allylation of aldehydes via Brønsted acid catalysis. Org. Lett. 2020, 22, 8967, DOI: 10.1021/acs.orglett.0c03366Google Scholar10ghttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXit1arsb3F&md5=e7fd9832fa39259b1eb4e0c3eba0dc18Enantioselective anti- and syn-(Borylmethyl)allylation of Aldehydes via Bronsted Acid CatalysisLiu, Jiaming; Chen, MingOrganic Letters (2020), 22 (22), 8967-8972CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)The enantioselective anti- and syn-(borylmethyl)allylation of aldehydes via phosphoric acid catalysis is reported. Both (E)- and (Z)-γ-borylmethyl allylboronate reagents were prepd. via the Cu-catalyzed highly stereoselective protoboration of 1,3-dienylboronate. Chiral phosphoric acid-catalyzed aldehyde allylation with either the (E)- or (Z)-allylboron reagent provided 1,2-anti- or 1,2-syn-adducts in good yields with high enantioselectivities. The application to the synthesis of morinol D was accomplished.(h) 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, DOI: 10.1002/anie.202107004Google Scholar10hhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXit1SqsLjK&md5=625a2db91a0c47923f956ef8b6f73202Stereochemical Control via Chirality Pairing: Stereodivergent Syntheses of Enantioenriched Homoallylic AlcoholsGao, Shang; Duan, Meng; Liu, Jiaming; Yu, Peiyuan; Houk, Kendall N.; Chen, MingAngewandte 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.(i) 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, DOI: 10.1039/D1SC04047BGoogle Scholar10ihttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXitVKnurzI&md5=b0f8cb247ce1981632f7b782ec1f28daCatalytic asymmetric transformations of racemic α-borylmethyl-(E)-crotylboronate via kinetic resolution or enantioconvergent reaction pathwaysGao, Shang; Liu, Jiaming; Chen, MingChemical 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.(j) Gao, S.; Duan, M.; Andreola, L. R.; Yu, P.; Wheeler, S. E.; Houk, K. N.; Chen, M. Unusual enantiodivergence in chiral Brønsted acid-catalyzed asymmetric allylation with β-alkenyl allylic boronates. Angew. Chem., Int. Ed. 2022, 61, e202208908 DOI: 10.1002/anie.202208908Google Scholar10jhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38XitlGlsL3P&md5=083d893b35c49dcdd026dcabdd1ca977Unusual Enantiodivergence in Chiral Broensted Acid-Catalyzed Asymmetric Allylation with β-Alkenyl Allylic BoronatesGao, Shang; Duan, Meng; Andreola, Laura R.; Yu, Peiyuan; Wheeler, Steven E.; Houk, Kendall N.; Chen, MingAngewandte Chemie, International Edition (2022), 61 (41), e202208908CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)A rare example of enantiodivergent aldehydes RCHO (R = Ph, naphthalen-2-yl, thiophen-3-yl, etc.) addn. with β-alkenyl allylic boronates CH2=CHC(=CH2)CH2R1 (R1 = 4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl, 4,4,5,5-tetrapropyl-1,3,2-dioxaborolan-2-yl, 4,4,6,6-tetramethyl-1,3,2-dioxaborinan-2-yl, etc.) via chiral Bronsted acid catalysis. 2,6-Di-9-anthracenyl-substituted chiral phosphoric acid-catalyzed asym. allylation using β-vinyl substituted allylic boronate that gave alcs. RCH(OH)CH2C(=CH2)CH=CH2 with R abs. configuration were reported. The sense of asym. induction of the catalyst in these reactions is opposite to those in prior reports. Moreover, in the presence of the same acid catalyst, the reactions with β-2-propenyl substituted allylic boronate CH3C(=CH2)C(=CH2)CH2Bpin generated homoallylic alc. products RCH(OH)CH2C(=CH2)C(=CH2)CH3 with S abs. configuration. Unusual substrate-catalyst C-H···π interactions in the favored reaction transition state were identified as the origins of obsd. enantiodivergence through DFT computational studies.
- 11(a) Jain, P.; Wang, H.; Houk, K. N.; Antilla, J. C. Brønsted acid catalyzed asymmetric propargylation of aldehydes. Angew. Chem., Int. Ed. 2012, 51, 1391, DOI: 10.1002/anie.201107407Google Scholar11ahttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhs12gtrrK&md5=1b78976d2d9f66826412e31f93bc7a71Bronsted acid-catalyzed asymmetric propargylation of aldehydesJain, Pankaj; Wang, Hao; Houk, Kendall N.; Antilla, Jon C.Angewandte Chemie, International Edition (2012), 51 (6), 1391-1394, S1391/1-S1391/41CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)A Bronsted acid-catalyzed propargylation of aldehydes with allenylboronate is described. Corresponding homopropargylic alcs. were obtained using this methods.(b) Reddy, L. R. Chiral Brønsted acid catalyzed enantioselective propargylation of aldehydes with allenylboronate. Org. Lett. 2012, 14, 1142, DOI: 10.1021/ol300075nGoogle Scholar11bhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhtFWhtrs%253D&md5=ab409111adb135d67f255c4e7cb51a0eChiral Bronsted Acid Catalyzed Enantioselective Propargylation of Aldehydes with AllenylboronateReddy, Leleti RajenderOrganic Letters (2012), 14 (4), 1142-1145CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)A highly enantioselective chiral Bronsted acid-catalyzed propargylation of aldehydes with allenylboronate is described. The reaction is shown to be practical and quite general with a broad substrate scope covering aryl, polyaryl, heteroaryl, α,β-unsatd., and aliph. aldehydes.(c) Chen, M.; Roush, W. R. Enantioselective synthesis of anti- and syn-homopropargyl alcohols via chiral Brønsted acid catalyzed asymmetric allenylboration reactions. J. Am. Chem. Soc. 2012, 134, 10947, DOI: 10.1021/ja3031467Google Scholar11chttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XptFWjt74%253D&md5=847f94eab34fdcbd6e7de9d05e14d2b4Enantioselective Synthesis of anti- and syn-Homopropargyl Alcohols via Chiral Bronsted Acid Catalyzed Asymmetric Allenylboration ReactionsChen, Ming; Roush, William R.Journal of the American Chemical Society (2012), 134 (26), 10947-10952CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Chiral Bronsted acid catalyzed asym. allenylboration reactions are described. Under optimized conditions, anti-homopropargyl alcs. are obtained in high yields with excellent diastereo- and enantioselectivities from stereochem. matched aldehyde allenylboration reactions with chiral allenylboronate catalyzed by the chiral phosphoric acid. The syn-isomers can also be obtained in good diastereoselectivities and excellent enantioselectivities from the mismatched allenylboration reactions of arom. aldehydes using allenylboronate in the presence of the enantiomeric phosphoric acid. The stereochem. of the Me group introduced into syn- and anti-homopropargyl alcs. is controlled by the chirality of the allenylboronate, whereas the configuration of the new hydroxyl stereocenter is controlled by the enantioselectivity of the chiral phosphoric acid catalyst used in these reactions. The synthetic utility of this methodol. was further demonstrated in highly diastereoselective syntheses of a variety of anti, anti-stereotriads, the direct synthesis of which has constituted a significant challenge using previous generations of aldol and crotylmetal reagents.(d) Tsai, A. S.; Chen, M.; Roush, W. R. Chiral Brønsted acid catalyzed enantioselective synthesis of anti-homopropargyl alcohols via kinetic resolution-aldehyde allenylboration using racemic allenylboronates. Org. Lett. 2013, 15, 1568, DOI: 10.1021/ol4003459Google Scholar11dhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXjvVahtLw%253D&md5=ca86e207c376ddeda7cc13195cdfcaeeChiral Bronsted acid catalyzed enantioselective synthesis of anti-homopropargyl alcohols via kinetic resolution-aldehyde allenylboration using racemic allenylboronatesTsai, Andy S.; Chen, Ming; Roush, William R.Organic Letters (2013), 15 (7), 1568-1571CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)A chiral phosphoric acid catalyzed kinetic resoln./allenylboration of racemic allenylboronates with aldehydes is described. Allenylboration of aldehydes with 2.8 equiv of allenylboronate (±)-1 in the presence of 10 mol % of catalyst (R)-2 provided anti-homopropargyl alcs. 3 in 83-95% yield with 9:1 to 20:1 diastereoselectivity and 73-95% ee. The catalyst enables the kinetic resoln. of the racemic allenylboronate (±)-1 to set the Me stereocenter and biases the facial attack of the aldehyde to set the stereochem. of the hydroxyl group in 3.(e) Wang, M.; Khan, S.; Miliordos, E.; Chen, M. Enantioselective syntheses of homopropargylic alcohols via asymmetric allenylboration. Org. Lett. 2018, 20, 3810, DOI: 10.1021/acs.orglett.8b01399Google Scholar11ehttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhtFWhurfJ&md5=71d97280faed42ec95483f578268b963Enantioselective Syntheses of Homopropargylic Alcohols via Asymmetric AllenylborationWang, Mengzhou; Khan, Shahriar; Miliordos, Evangelos; Chen, MingOrganic Letters (2018), 20 (13), 3810-3814CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)A chiral phosphoric acid catalyzed allenylboration reaction is reported. Homopropargyl alcs. with an internal alkyne unit were obtained in good yields with high enantioselectivities under the developed conditions.
- 12(a) Reddy, L. R. Chiral Brønsted acid catalyzed enantioselective allenylation of aldehydes. Chem. Commun. 2012, 48, 9189, DOI: 10.1039/c2cc34371aGoogle Scholar12ahttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38Xht1ajtL7F&md5=008740ed161f5d0a970e145a83fa4e28Chiral Bronsted acid catalyzed enantioselective allenylation of aldehydesReddy, Leleti RajenderChemical Communications (Cambridge, United Kingdom) (2012), 48 (73), 9189-9191CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)A versatile and highly enantioselective chiral Bronsted acid-catalyzed allenylation of aldehydes with propargyl borolane is reported. The reaction is shown to be practical and quite general with a broad substrate scope covering aryl, heteroaryl, α,β-unsatd., and aliph. aldehydes.(b) Wang, M.; Khan, S.; Miliordos, E.; Chen, M. Enantioselective allenylation of aldehydes via Brønsted acid catalysis. Adv. Synth. Catal. 2018, 360, 4634, DOI: 10.1002/adsc.201801080Google Scholar12bhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXitVGlt7vF&md5=7bb7f588294d755d860a684bd7f430d1Enantioselective Allenylation of Aldehydes via Bronsted Acid CatalysisWang, Mengzhou; Khan, Shahriar; Miliordos, Evangelos; Chen, MingAdvanced Synthesis & Catalysis (2018), 360 (23), 4634-4639CODEN: ASCAF7; ISSN:1615-4150. (Wiley-VCH Verlag GmbH & Co. KGaA)An enantioselective allenylation of aldehydes catalyzed by a chiral, nonracemic phosphoric acid was reported. Under the developed conditions, 1,1'-disubstituted allenic alcs. were obtained in 64-98% yields with 88-99% ee. Computational studies were conducted to probe the origin of asym. induction. Mechanistic studies suggest that the pinacol moiety of the propargylboronate is crit. to the enantioselectivity of the reaction that was supported by exptl. data.
- 13(a) Grayson, M. N.; Pellegrinet, S. C.; Goodman, J. M. Mechanistic insights into the BINOL-derived phosphoric acid-catalyzed asymmetric allylboration of aldehydes. J. Am. Chem. Soc. 2012, 134, 2716, DOI: 10.1021/ja210200dGoogle Scholar13ahttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XlvFaq&md5=4eac2953c47f8bb50d6e44c6ce899216Mechanistic Insights into the BINOL-Derived Phosphoric Acid-Catalyzed Asymmetric Allylboration of AldehydesGrayson, Matthew N.; Pellegrinet, Silvina C.; Goodman, Jonathan M.Journal of the American Chemical Society (2012), 134 (5), 2716-2722CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)BINOL-derived phosphoric acids catalyze the asym. allylboration of aldehydes. DFT and QM/MM hybrid calcns. showed that the reaction proceeds via a transition state involving both a hydrogen-bonding interaction from the catalyst hydroxyl group to the pseudoaxial oxygen of the cyclic boronate and a stabilizing interaction from the phosphoryl oxygen of the catalyst to the formyl hydrogen of the aldehyde. These interactions lower the energy of the transition structure and provide extra rigidity to the system. This mechanistic pathway is consistent with the exptl. obsd. enantioselectivity except in one case. We have used our model's predictions to guide our own exptl. work. The conflict is resolved in favor of our calcns.(b) Wang, H.; Jain, P.; Antilla, J. C.; Houk, K. N. Origins of stereoselectivities in chiral phosphoric acid catalyzed allylborations and propargylations of aldehydes. J. Org. Chem. 2013, 78, 1208, DOI: 10.1021/jo302787mGoogle Scholar13bhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXkt1ygtg%253D%253D&md5=075199c52693806970b3f61952f1e8baOrigins of Stereoselectivities in Chiral Phosphoric Acid Catalyzed Allylborations and Propargylations of AldehydesWang, Hao; Jain, Pankaj; Antilla, Jon C.; Houk, K. N.Journal of Organic Chemistry (2013), 78 (3), 1208-1215CODEN: JOCEAH; ISSN:0022-3263. (American Chemical Society)The chiral BINOL-H3PO4 catalyzed allylboration and propargylation reactions were studied with d. functional theory (B3LYP and B3LYP-D3). Two different models were recently proposed for these reactions by Goodman and the authors' group, resp. In Goodman's model for allylborations, the catalyst interacts with the boronate pseudoaxial oxygen. By contrast, the authors' model for propargylations predicts that the catalyst interacts with the boronate pseudoequatorial oxygen. In both models, the H3PO4 stabilizes the transition state by forming a strong H bond with the oxygen of the boronate and is oriented by a formyl H bond (Goodman model) and by other electrostatic attractions in the authors' model. Both of these models have now been restudied for both allylborations and propargylations. For the most effective catalyst for these reactions, the lowest energy transition state corresponds to Goodman's axial model, while the best transition state leading to the minor enantiomer involves the equatorial model. The high enantioselectivity obsd. with only the bulkiest catalyst arises from the steric interactions between the substrates and the bulky groups on the catalyst, and the resulting necessity for distortion of the catalyst in the disfavored transition state.(c) Grayson, M. N.; Goodman, J. M. Understanding the mechanism of the asymmetric propargylation of aldehydes promoted by 1,1’-bi-2-naphthol-derived catalysts. J. Am. Chem. Soc. 2013, 135, 6142, DOI: 10.1021/ja3122137Google Scholar13chttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXksFSktL8%253D&md5=62409c6d798dba54a22550abb62082f9Understanding the Mechanism of the Asymmetric Propargylation of Aldehydes Promoted by 1,1'-Bi-2-naphthol-Derived CatalystsGrayson, Matthew N.; Goodman, Jonathan M.Journal of the American Chemical Society (2013), 135 (16), 6142-6148CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)1,1'-Bi-2-naphthol (BINOL)-derived phosphoric acids catalyze the asym. propargylation of aldehydes. D. functional theory (DFT) calcns. showed that the reaction proceeds via a six-membered transition structure (TS) in which the catalyst Bronsted acidic site interacts with the pseudoaxial cyclic boronate oxygen and the phosphoryl oxygen interacts with the formyl proton. This model accurately predicts the stereochem. outcome obsd. exptl. Replacement of the phosphoric acid hydroxyl group with an N-triflyl moiety has been included in the model by calcn. and a broader understanding achieved by qual. assessment of similar reactions. We present a qual. guide to rationalizing the exptl. outcome and use this to make a prediction which was confirmed exptl.
- 14(a) Miura, T.; Nakahashi, J.; Zhou, W.; Shiratori, Y.; Stewart, S. G.; Murakami, M. Enantioselective synthesis of anti-1,2-oxaborinan-3-enes from aldehydes and 1,1-di(boryl)alk-3-enes using ruthenium and chiral phosphoric acid catalysts. J. Am. Chem. Soc. 2017, 139, 10903, DOI: 10.1021/jacs.7b06408Google Scholar14ahttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhtFOmtrnF&md5=9c4c524e47036cc592bd48da72691167Enantioselective Synthesis of anti-1,2-Oxaborinan-3-enes from Aldehydes and 1,1-Di(boryl)alk-3-enes Using Ruthenium and Chiral Phosphoric Acid CatalystsMiura, Tomoya; Nakahashi, Junki; Zhou, Wang; Shiratori, Yota; Stewart, Scott G.; Murakami, MasahiroJournal of the American Chemical Society (2017), 139 (31), 10903-10908CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)A cationic Ru(II) complex catalyzes double-bond transposition of 1,1-di(boryl)alk-3-enes to generate in situ 1,1-di(boryl)alk-2-enes, which then undergo chiral H3PO4 catalyzed allylation of aldehydes producing homoallylic alcs. with a (Z)-vinylboronate moiety. 1,2-Anti stereochem. is installed in an enantioselective manner. The (Z)-geometry forged in the products allows their isolation in a form of 1,2-oxaborinan-3-enes, upon which further synthetic transformations are operated.(b) Miura, T.; Oku, N.; Murakami, M. Diastereo- and enantioselective synthesis of (E)-δ-boryl-substituted anti-homoallylic alcohols in two steps from terminal alkynes. Angew. Chem., Int. Ed. 2019, 58, 14620, DOI: 10.1002/anie.201908299Google Scholar14bhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhs12jurrO&md5=e8959ffe827ecca629f3c0030547c3a5Diastereo- and Enantioselective Synthesis of (E)-δ-Boryl-Substituted anti-Homoallylic Alcohols in Two Steps from Terminal AlkynesMiura, Tomoya; Oku, Naoki; Murakami, MasahiroAngewandte Chemie, International Edition (2019), 58 (41), 14620-14624CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)The authors report the highly diastereo- and enantioselective prepn. of (E)-δ-boryl-substituted anti-homoallylic alcs. in two steps from terminal alkynes. This method consists of a Co(II)-catalyzed 1,1-diboration reaction of terminal alkynes with B2pin2 and a Pd(I)-mediated asym. allylation reaction of the resulting 1,1-di(boryl)alk-1-enes with aldehydes in the presence of a chiral H3PO4. Propyne, which is produced as the byproduct during petroleum refining, could be used as the starting material to construct homoallylic alcs. that are otherwise difficult to synthesize with high stereocontrol.(c) Gao, S.; Duan, M.; Houk, K. N.; Chen, M. Chiral phosphoric acid dual-function catalysis: asymmetric allylation with α-vinyl allylboron reagents. Angew. Chem., Int. Ed. 2020, 59, 10540, DOI: 10.1002/anie.202000039Google Scholar14chttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXnslGmtrw%253D&md5=47fc81077bc5b2e362c89d70d485267bChiral Phosphoric Acid Dual-Function Catalysis: Asymmetric Allylation with α-Vinyl Allylboron ReagentsGao, Shang; Duan, Meng; Houk, Kendall N.; Chen, MingAngewandte Chemie, International Edition (2020), 59 (26), 10540-10548CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)We report a dual function asym. catalysis by a chiral phosphoric acid catalyst that controls both enantioselective addn. of an achiral α-vinyl allylboronate to aldehydes and pseudo-axial orientation of the α-vinyl group in the transition state. The reaction produces dienyl homoallylic alcs. with high Z-selectivities and enantioselectivities. Computational studies revealed that minimization of steric interactions between the alkyl groups of the diol on boron and the chiral phosphoric acid catalyst influence the orientation of α-vinyl substituent of the allylboronate reagent to occupy a pseudo-axial position in the transition state.(d) Gao, S.; Duan, M.; Shao, Q.; Houk, K. N.; Chen, M. Development of α, α-disubstituted crotylboronate reagents and stereoselective crotylation via Brønsted or Lewis acid catalysis. J. Am. Chem. Soc. 2020, 142, 18355, DOI: 10.1021/jacs.0c04107Google Scholar14dhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXitVGlu73I&md5=23e4240177bfd3e62da15f93fff04a3aDevelopment of α,α-Disubstituted Crotylboronate Reagents and Stereoselective Crotylation via Bronsted or Lewis Acid CatalysisGao, Shang; Duan, Meng; Shao, Qianzhen; Houk, K. N.; Chen, MingJournal of the American Chemical Society (2020), 142 (43), 18355-18368CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The development of α,α-disubstituted crotylboronate reagents is reported. Chiral Bronsted acid-catalyzed asym. aldehyde addn. with the developed E-crotylboron reagent gave (E)-anti-1,2-oxaborinan-3-enes with excellent enantioselectivities and E-selectivities. With BF3·OEt2 catalysis, the stereoselectivity is reversed, and (Z)-δ-boryl-anti-homoallylic alcs. were obtained with excellent Z-selectivities from the same E-crotylboron reagent. The Z-crotylboron reagent also participates in BF3·OEt2-catalyzed crotylation to furnish (Z)-δ-boryl-syn-homoallylic alcs. with good Z-selectivities. DFT computations establish the origins of obsd. enantio- and stereoselectivities of chiral Bronsted acid-catalyzed asym. allylation. Stereochem. models for BF3·OEt2-catalyzed reactions probably rationalize the Z-selective allyl addns. These reactions generate highly valuable homoallylic alc. products with a stereodefined trisubstituted alkene unit. The synthetic utility is further demonstrated by the total syntheses of salinipyrones A and B.(e) Chen, J.; Chen, M. Enantioselective syntheses of (Z)-6′-boryl-anti-1,2-oxaborinan-3-enes via a dienylboronate protoboration and asymmetric allylation reaction sequence. Org. Lett. 2020, 22, 7321, DOI: 10.1021/acs.orglett.0c02657Google Scholar14ehttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhslOitr3I&md5=3f32fbff9243342497f55eff5ae0c2b8Enantioselective Syntheses of (Z)-6'-Boryl-anti-1,2-oxaborinan-3-enes via a Dienylboronate Protoboration and Asymmetric Allylation Reaction SequenceChen, Jichao; Chen, MingOrganic Letters (2020), 22 (18), 7321-7326CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)Asym. allylboration of aldehydes RCHO with allyltriboronate pinBCH2CH:CHCH(Bpin)2 afforded chiral 1,2-oxaborinanes I. Enantioselective synthesis of 6'-boryl-anti-1,2-oxaborinan-3-enes is reported. A Cu-catalyzed highly stereoselective 1,4-protoboration of 1,1-bisboryl-1,3-butadiene is developed to generate (E)-α,δ-bisboryl-crotylboronate. Chiral phosphoric acid-catalyzed asym. allylboration of aldehydes with the boron reagent produces 6'-boryl-anti-1,2-oxaborinan-3-enes with excellent Z-selectivities and enantioselectivities. The product contains a vinyl and alkyl boronate unit that can directly participate in a variety of subsequent transformations.(f) Zhang, Z.; Liu, J.; Gao, S.; Su, B.; Chen, M. Highly stereoselective syntheses of α,α-disubstituted (E)- and (Z)-crotylboronates. J. Org. Chem. 2023, 88, 3288, DOI: 10.1021/acs.joc.2c02606Google ScholarThere is no corresponding record for this reference.
- 15Hoffmann, R. W. Allylic 1,3-strain as a controlling factor in stereoselective transformations. Chem. Rev. 1989, 89, 1841, DOI: 10.1021/cr00098a009Google Scholar15https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL1MXmtlWnurc%253D&md5=91540e91c0c31a112831dd5ac9d73f4dAllylic 1,3-strain as a controlling factor in stereoselective transformationsHoffmann, Reinhard W.Chemical Reviews (Washington, DC, United States) (1989), 89 (8), 1841-60CODEN: CHREAY; ISSN:0009-2665.A review with 155 refs. on the manifestation of allylic strain in the stereochem. of a host of chem. reactions, including cyclizations, intermol. addn., hydrogenation, cyclopropanation, and others.
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Abstract
Figure 1
Figure 1. Selected natural products containing the 1,3-butadienyl-2-carbinol motif or the deoxy-analog.
Scheme 1
Scheme 1. Approaches to 1,3-Butadienyl-2-carbinolsScheme 2
Scheme 2. Syntheses of Boron Reagents 1 and Evaluation of the Conditions for Reactions with Boronate 1aaaReaction conditions: boronate 1a (0.12 mmol, 1.2 equiv), benzaldehyde (0.1 mmol, 1.0 equiv), catalyst (5 mol %), 4 Å molecular sieves (50 mg), toluene (0.3 mL), −45 °C.
bThe Z/E ratios were determined by 1H NMR analyses of the crude reaction products.
cYields of isolated products are listed.
dThe enantiomeric excesses were determined by modified Mosher ester analyses.
eThe reaction was conducted at rt.
fThe reaction was conducted in CH2Cl2.
Scheme 3
Scheme 3. Scope of the Aldehyde for Acid (R)-A-Catalyzed Asymmetric Allylation with Boronate 1aa–daReaction conditions: boronate 1a (0.12 mmol, 1.2 equiv), aldehyde (0.1 mmol, 1.0 equiv), phosphoric acid (R)-A (5 mol %), 4 Å molecular sieves (50 mg), toluene (0.3 mL), −45 °C.
bYields of isolated products 2 are listed.
cThe Z/E ratios were determined by 1H NMR analyses of the crude reaction products.
dThe enantiomeric excesses were determined by modified Mosher ester analyses.
Scheme 4
Scheme 4. Chiral Phosphoric-Acid-Catalyzed Asymmetric Aldehyde Addition with Homoallenyl boronates 1b–da–daReaction conditions: allylboronate 1a (0.12 mmol, 1.2 equiv), aldehyde (0.1 mmol, 1.0 equiv), phosphoric acid (R)-A (5 mol %), 4 Å molecular sieves (50 mg), toluene (0.3 mL), −45 °C.
bYields of isolated products are listed.
cThe Z/E ratios were determined by 1H NMR analyses of the crude reaction products.
dThe enantiomeric excesses were determined by modified Mosher ester analysis.
Scheme 5
Scheme 5. Transition State Analyses of Aldehyde Addition with Boron Reagents 5 and 1aScheme 6
Scheme 6. Transition State Analyses of Chiral Phosphoric-Acid-Catalyzed Aldehyde Addition with Reagent 1aReferences
This article references 15 other publications.
- 1(a) Kobayashi, J.; Tsuda, M.; Ishibashi, M.; Shigemori, H.; Yamasu, T.; Hirota, H.; Sasaki, T. Amphidinolide F, a new cytotoxic macrolide from the marine dinoflagellate Amphidinium sp. J. Antibiot. 1991, 44, 1259, DOI: 10.7164/antibiotics.44.12591ahttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK38Xht1Cms74%253D&md5=712acfcefd7a656a0a12de2d0589a2eaAmphidinolide F, a new cytotoxic macrolide from the marine dinoflagellate Amphidinium spKobayashi, Junichi; Tsuda, Masashi; Ishibashi, Masami; Shigemori, Hideyuki; Yamasu, Terufumi; Hirota, Hiroshi; Sasaki, TakumaJournal of Antibiotics (1991), 44 (11), 1259-61CODEN: JANTAJ; ISSN:0021-8820.A new cytotoxic macrocyclic lactose, termed amphidinolide F, was isolated from Amphidinium sp. Its structure was established by physiochem. procedures including 1H and 14C NMR spectroscopy. Amphidinolide F is considered to be biogenetically closely related to amphidinolide C, the former possibly being a precursor of the latter. Amphidinolide F exhibited cytotoxic activity against murine lymphoma L1210 cells and human epidermoid carcinoma KB cells in vitro with IC50 values of 1.5 and 3.2 μg/mL, resp.(b) Bauer, I.; Maranda, L.; Shimizu, Y.; Peterson, R. W.; Cornell, L.; Steiner, J. R.; Clardy, J. The structures of amphidinolide B isomers: strongly cytotoxic macrolides produced by a free-swimming dinoflagellate, Amphidinium sp. J. Am. Chem. Soc. 1994, 116, 2657, DOI: 10.1021/ja00085a071There is no corresponding record for this reference.(c) Areche, C.; Sepulveda, B.; Martin, A. S.; Garcia-Beltran, O.; Simirgiotis, M.; Cañete, A. An unusual mulinane diterpenoid from the Chilean plant Azorella trifurcata (Gaertn) Pers. An unusual mulinane diterpenoid from the Chilean plant Azorella trifurcata (Gaertn) Pers. Org. Biomol. Chem. 2014, 12, 6406, DOI: 10.1039/C4OB00966EThere is no corresponding record for this reference.
- 2(a) Nicolaou, K. C.; Bulger, P. G.; Brenzovich, W. E. Synthesis of iso-epoxy-amphidinolide N and des-epoxy-caribenolide I structures. Revised strategy and final stages. Org. Biomol. Chem. 2006, 4, 2158, DOI: 10.1039/b602021f2ahttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28XkvFOmsb4%253D&md5=be673c0f8b792c797661cf91a045f193Synthesis of iso-epoxy-amphidinolide N and des-epoxy-caribenolide I structures. Revised strategy and final stagesNicolaou, K. C.; Bulger, Paul G.; Brenzovich, William E.Organic & Biomolecular Chemistry (2006), 4 (11), 2158-2183CODEN: OBCRAK; ISSN:1477-0520. (Royal Society of Chemistry)A general and highly convergent synthetic route to the macrocyclic core structures of the antitumor agents amphidinolide N and caribenolide I has been developed, and the total synthesis of iso-epoxy-amphidinolide N and des-epoxy-caribenolide I structures is described. Central to the revised strategy was the use of a Horner-Wadsworth-Emmons olefination between a β-ketophosphonate and an aldehyde to construct the C1-C13 sector common to both amphidinolide N and caribenolide I. Stereoselective alkylation allowed for the rapid assembly of the complete caribenolide I carbon skeleton. Key steps in the completion of the synthesis of des-epoxy-caribenolide I structure I included hydrolysis of a sensitive Me ester using Me3SnOH, followed by regioselective macrolactonization of the resulting diol seco-acid and global deprotection. An analogous sequence of late-stage manoeuvres was used to arrive at the fully deprotected des-epoxy-amphidinolide N framework, obtained as a mixt. of hemiacetal II and its bicyclic acetal. Regio- and diastereoselective epoxidn. of the C6 methylene group in the bicyclic acetal provided access to iso-epoxy-amphidinolide N stereoisomer. Several of the prepd. compds. were tested for cytotoxicity against human tumor cell lines, and none showed activity.(b) Matsuura, F.; Peters, R.; Anada, M.; Harried, S. S.; Hao, J.; Kishi, Y. Unified total synthesis of pteriatoxins and their diastereomers. J. Am. Chem. Soc. 2006, 128, 7463, DOI: 10.1021/ja06189542bhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28XkslKhsbo%253D&md5=bb303ae03f212261a289efbc59528368Unified Total Synthesis of Pteriatoxins and Their DiastereomersMatsuura, Fumiyoshi; Peters, Rene; Anada, Masahiro; Harried, Scott S.; Hao, Junliang; Kishi, YoshitoJournal of the American Chemical Society (2006), 128 (23), 7463-7465CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)A unified total synthesis is reported to access all of the possible diastereomers of pteriatoxins A-C, with the use of an intramol. Diels-Alder reaction as the key step to form the carbo-macrocyclic core structure. The C34/C35-diol protecting groups were found to have significant effects on both the exo/endo-selectivity and the exo-facial selectivity of the intramol. Diels-Alder process.(c) Trost, B. M.; Bai, W. J.; Stivala, C. E.; Hohn, C.; Poock, C.; Heinrich, M.; Xu, S.; Rey, J. Enantioselective synthesis of des-epoxy-amphidinolide N. J. Am. Chem. Soc. 2018, 140, 17316, DOI: 10.1021/jacs.8b118272chttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXit1OqsbzK&md5=36bff08be25376d942d4db13375c90fcEnantioselective Synthesis of des-Epoxy-Amphidinolide NTrost, Barry M.; Bai, Wen-Ju; Stivala, Craig E.; Hohn, Christoph; Poock, Caroline; Heinrich, Marc; Xu, Shiyan; Rey, JullienJournal of the American Chemical Society (2018), 140 (49), 17316-17326CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The synthesis of des-epoxy-amphidinolide N (I) was achieved in 22 longest linear and 33 total steps. Three generations of synthetic endeavors are reported herein. During the first generation, our key stitching strategy that highlighted an intramol. Ru-catalyzed alkene-alkyne (Ru AA) coupling and a late-stage epoxidn. proved successful, but the installation of the α,α'-dihydroxyl ketone motif employing a dihydroxylation method was problematic. Our second generation of synthetic efforts addressed the scalability problem of the southern fragment synthesis and significantly improved the efficiency of the atom-economical Ru AA coupling, but suffered from several protecting group-based issues that proved insurmountable. Finally, relying on a judicious protecting group strategy together with concise fragment prepn., des-epoxy-amphidinolide N was achieved in a convergent fashion. Calcns. disclose a hydrogen-bonding bridge within amphidinolide N. Comparisons of 13C NMR chem. shift differences using our synthetic des-epoxy-amphidinolide N suggest that amphidinolide N and carbenolide I are probably identical.(d) Giessert, A. J.; Diver, S. T. Equilibrium control in enyne metathesis: crossover studies and the kinetic reactivity of (E,Z)-1,3-disubstituted-1,3-dienes. J. Org. Chem. 2005, 70, 1046, DOI: 10.1021/jo04822092dhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXjtFGitw%253D%253D&md5=23084f8a505671055c6498b0293e65f3Equilibrium Control in Enyne Metathesis: Crossover Studies and the Kinetic Reactivity of (E,Z)-1,3-Disubstituted-1,3-DienesGiessert, Anthony J.; Diver, Steven T.Journal of Organic Chemistry (2005), 70 (3), 1046-1049CODEN: JOCEAH; ISSN:0022-3263. (American Chemical Society)The stereoselectivity of diene bond formation in the ruthenium-carbene mediated intermol. enyne metathesis was studied. Initial reaction between an alkyne and 1-hexene gave mixts. of E- and Z-isomers in the newly formed 1,3-diene. However, over time the mixts. equilibrated to form mostly the diene of the E-configuration. To evaluate individual reactivity of the E- and Z-dienes, they were independently synthesized. The E-diene was found to be kinetically-stable under nominal metathesis conditions while the Z-diene isomerized to the E-isomer. The Z-isomeric dienes were found to react with other alkenes to produce a new diene of E-configuration. A secondary metathesis mechanism involving ruthenium alkylidene intermediates was invoked to explain the dynamic stereochem. obsd. in this study.
- 3(a) Trost, B. M.; Papillon, J. P. N. Alkene–Alkyne Coupling as a Linchpin: An efficient and convergent synthesis of amphidinolide P. J. Am. Chem. Soc. 2004, 126, 13618, DOI: 10.1021/ja045449x3ahttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXnvFGgsLo%253D&md5=f028ee178eb29b085301f76ce373f87eAlkene-alkyne coupling as a linchpin: an efficient and convergent synthesis of amphidinolide PTrost, Barry M.; Papillon, Julien P. N.Journal of the American Chemical Society (2004), 126 (42), 13618-13619CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)A short and efficient synthesis of the cytotoxic macrolide amphidinolide P is described. A remarkably chemo- and regioselective ruthenium-catalyzed alkene-alkyne coupling allows for a convergent synthesis and demonstrates that both enynes and β-lactones are suitable coupling partners. This work also features a novel strategy for the prepn. of macrolactones via intramol. transesterification of β-lactones. The target structure was prepd. in 15 steps for the longest linear sequence and 10% overall yield, 24 steps total.(b) Zhang, W.; Carter, R. G. Synthetic studies toward amphidinolide B1: Synthesis of the C9–C26 fragment. Org. Lett. 2005, 7, 4209, DOI: 10.1021/ol051544e3bhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXot1WjtLk%253D&md5=5db553f2c4ed7efe89ccf998bd6253cfSynthetic Studies toward Amphidinolide B1: Synthesis of the C9-C26 FragmentZhang, Wei; Carter, Rich G.Organic Letters (2005), 7 (19), 4209-4212CODEN: ORLEF7; ISSN:1523-7060. (American Chemical Society)The synthesis of the C9-C26 portion I of amphidinolide B1 is described. A Fleming allylation followed by elimination was employed for the construction of the C13-C15 diene portion. Sharpless asym. dihydroxylation was utilized for regioselective functionalization of a styrene-derived alkene, in the presence of the C13-C15 diene functionality. A highly diastereoselective aldol reaction was developed to establish the C18 stereochem.(c) Va, P.; Roush, W. R. Total synthesis of amphidinolide E. J. Am. Chem. Soc. 2006, 128, 15960, DOI: 10.1021/ja066663j3chttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28Xht1Clu7vN&md5=9fa7b9b16db69ff68d937de9c1975791Total Synthesis of Amphidinolide EVa, Porino; Roush, William R.Journal of the American Chemical Society (2006), 128 (50), 15960-15961CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)A convergent and highly stereocontrolled synthesis of amphidinolide E (I) has been accomplished. The synthesis features a highly diastereoselective (>20:1) BF3·Et2O promoted [3+2] annulation reaction between aldehyde II and allylsilane III to afford substituted THF IV.(d) Clark, J. S.; Yang, G.; Osnowski, A. P. Synthesis of the C1–C17 fragment of amphidinolides C, C2, C3, and F. Org. Lett. 2013, 15, 1460, DOI: 10.1021/ol40048383dhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXksFSrtLw%253D&md5=06f140200f51ad7520929f9f9cf800e2Synthesis of the C-1-C-17 Fragment of Amphidinolides C, C2, C3, and FClark, J. Stephen; Yang, Guang; Osnowski, Andrew P.Organic Letters (2013), 15 (7), 1460-1463CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)The C1-C17 fragment, I, of amphidinolides C, C2, C3, and F has been constructed from a trans-2,5-disubstituted dihydrofuranone II prepd. by diastereoselective rearrangement of a free or metal-bound oxonium ylide generated from a metal carbenoid (no data). The dihydrofuranone was converted into aldehyde III, which corresponds to the C1-C8 framework, and this was coupled to the C9-C17 unit IV by nucleophilic addn. of a vinylic anion.
- 4(a) Wang, M.; Gao, S.; Chen, M. Stereoselective syntheses of (E)-γ′,δ-bisboryl-substituted syn-homoallylic alcohols via chemoselective aldehyde allylboration. Org. Lett. 2019, 21, 2151, DOI: 10.1021/acs.orglett.9b004614ahttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXks1Chtr8%253D&md5=06739d8fddb925c66b6ddc86ec7ef254Stereoselective Syntheses of (E)-γ',δ-Bisboryl-Substituted syn-Homoallylic Alcohols via Chemoselective Aldehyde AllylborationWang, Mengzhou; Gao, Shang; Chen, MingOrganic Letters (2019), 21 (7), 2151-2155CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)The development of a novel (Z)-α,δ-bisboryl-substituted crotylboron reagent (Z)-pinBCH2CH:CHCH(Bpin)2 (2) is reported. Ni-catalyzed 1,4-diboration of dienylboronate provided the targeted crotylboronate in good yield with high regio- and stereoselectivity. Chemo- and stereoselective addn. of this crotylboron reagent to aldehydes RCHO followed by protection of the resulting secondary hydroxyl group gave TES-protected homoallylic alcs. I bearing an alkyl and a vinyl boronate groups with high stereoselectivities.(b) Gao, S.; Chen, J.; Chen, M. (Z)-α-Boryl-crotylboron reagents via Z-selective alkene isomerization and application to stereoselective syntheses of (E)-δ-boryl-syn-homoallylic alcohols. Chem. Sci. 2019, 10, 3637, DOI: 10.1039/C9SC00226J4bhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXlt12htbw%253D&md5=39fd1a0691236ad8e0b211468f38a5c4(Z)-α-Boryl-crotylboron reagents via Z-selective alkene isomerization and application to stereoselective syntheses of (E)-δ-boryl-syn-homoallylic alcoholsGao, Shang; Chen, Jichao; Chen, MingChemical Science (2019), 10 (12), 3637-3642CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)Stereoselective synthesis of (Z)-α-boryl-crotylboronate is developed. Ni-catalyzed Z-selective alkene isomerization of α-boryl substituted homoallylboronate provided the targeted (Z)-crotylboronate with high selectivity. Stereoselective addn. of the novel crotylboron reagent to aldehydes gave (E)-δ-boryl-substituted syn-homoallylic alcs. with excellent diastereoselectivities. The vinyl boronate unit in the products can be directly used for a subsequent C-C bond-forming transformation as illustrated in the synthesis of the C1-7 fragment of the natural products nannocystin A and nannocystin Ax.(c) 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, DOI: 10.1021/acs.orglett.1c036284chttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXis1eqtLnM&md5=faa1c7c9f2a9033283c14a03e66925a0Development of α-Borylmethyl-(Z)-crotylboronate Reagent and Enantioselective Syntheses of (E)-δ-Hydroxymethyl-syn-homoallylic Alcohols via Highly Stereoselective AllylborationLiu, Jiaming; Gao, Shang; Chen, MingOrganic 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.(d) Chen, J.; Miliordos, E.; Chen, M. Highly diastereo- and enantioselective synthesis of 3,6’-bisboryl-anti-1,2-oxaborinan-3-enes: an entry to enantioenriched homoallylic alcohols with a stereodefined trisubstituted alkene. Angew. Chem., Int. Ed. 2021, 60, 840, DOI: 10.1002/anie.2020064204dhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXitlWnt77P&md5=0b7baa6af0d1c00d3abe69652459fbc7Highly Diastereo- and Enantioselective Synthesis of 3,6'-Bisboryl-anti-1,2-oxaborinan-3-enes: An Entry to Enantioenriched Homoallylic Alcohols with A Stereodefined Trisubstituted AlkeneChen, Jichao; Miliordos, Evangelos; Chen, MingAngewandte Chemie, International Edition (2021), 60 (2), 840-848CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)A Cu-catalyzed regio-, diastereo-, and enantioselective carboboration of 1,1-bisboryl-1,3-butadiene is developed to generate enantioenriched 3,6'-bisboryl-anti-1,2-oxaborinan-3-enes. DFT calcns. indicate that the initial diene 1,2-borocupration forms a 3η-allylic Cu as the most stable intermediate. Subsequent aldehyde addn., however, operates under Curtin-Hammett control via a more reactive α,α-bisboryl tertiary allylcopper species to furnish products with high enantioselectivities. The three boryl groups in the products are properly differentiated and can undergo a variety of chemoselective transformations to produce enantioenriched homoallylic alcs. with a stereodefined trisubstituted alkene.(e) Liu, J.; Gao, S.; Miliordos, E.; Chen, M. Asymmetric syntheses of (Z)- or (E)-β,γ-unsaturated ketones via silane-controlled enantiodivergent catalysis. J. Am. Chem. Soc. 2023, 145, 19542, DOI: 10.1021/jacs.3c025954ehttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3sXhslKksLzF&md5=286450516bb84a7eefa0aa50d260afadAsymmetric Syntheses of (Z)- or (E)-β,γ-Unsaturated Ketones via Silane-Controlled Enantiodivergent CatalysisLiu, Jiaming; Gao, Shang; Miliordos, Evangelos; Chen, MingJournal of the American Chemical Society (2023), 145 (36), 19542-19553CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Cu-catalyzed highly stereoselective and enantiodivergent synthesis of (Z)- or (E)-β,γ-unsatd. ketones from 1,3-butadienyl silanes were developed. The nature of silyl group of dienes had a significant impact on stereo- and enantioselectivity of reactions. Under developed catalytic systems, reactions of acyl fluorides with phenyldimethylsilyl-substituted 1,3-diene gave (Z)-β,γ-unsatd. ketones bearing an α-tertiary stereogenic center with excellent enantioselectivities and high Z-selectivities, where reactions with triisopropylsilyl-substituted 1,3-butadiene formed (E)-β,γ-unsatd. ketones with high optical purities and excellent E-selectivities. The products generated from reactions contain three functional groups with orthogonal chem. reactivities, which can undergo a variety of transformations to afford synthetically valuable intermediates.(f) Gao, S.; Liu, J.; Troya, D.; Chen, M. Copper-catalyzed asymmetric acylboration of 1,3-butadienylboronate with acyl fluorides. Angew. Chem., Int. Ed. 2023, 62, e202304796 DOI: 10.1002/anie.2023047964fhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3sXhvFehtb3F&md5=80bdb29eef4e2e4a92d5380227860c12Copper-Catalyzed Asymmetric Acylboration of 1,3-Butadienylboronate with Acyl FluoridesGao, Shang; Liu, Jiaming; Troya, Diego; Chen, MingAngewandte Chemie, International Edition (2023), 62 (43), e202304796CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)We report herein a Cu-catalyzed regio-, diastereo- and enantioselective acylboration of 1,3-butadienylboronate with acyl fluorides. Under the developed conditions, the reactions provide (Z)-β,γ-unsatd. ketones bearing an α-tertiary stereocenter with high Z-selectivity and excellent enantioselectivities. While direct access to highly enantioenriched E-isomers was not successful, we showed that such mols. can be synthesized with excellent E-selectivity and optical purities via Pd-catalyzed alkene isomerization from the corresponding Z-isomers. The orthogonal chem. reactivities of the functional groups embedded in the ketone products allow for diverse chemoselective transformations, which provides a valuable platform for further derivatization.
- 5(a) Lachance, H.; Hall, D. G. Allylboration of carbonyl compounds. Org. React. 2009, 73, 1, DOI: 10.1002/0471264180.or073.01There is no corresponding record for this reference.(b) Yus, M.; González-Gómez, J. C.; Foubelo, F. Catalytic enantioselective allylation of carbonyl compounds and imines. Chem. Rev. 2011, 111, 7774, DOI: 10.1021/cr10044745bhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhtFygu7zJ&md5=df838d62c3869a07067c7c7890e3193dCatalytic enantioselective allylation of carbonyl compounds and iminesYus, Miguel; Gonzalez-Gomez, Jose C.; Foubelo, FranciscoChemical Reviews (Washington, DC, United States) (2011), 111 (12), 7774-7854CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)A review. Methodologies on the catalytic enantioselective addn. of allylic nucleophiles to carbonyl compds., imines (mostly with N-allyl, -aryl, -benzyl, and -sulfonyl substituents), and imine derivs. (hydrazones) will be considered, paying special attention to the most useful reactions from a synthetic point of view.(c) Yus, M.; González-Gómez, J. C.; Foubelo, F. Diastereoselective allylation of carbonyl compounds and imines: application to the synthesis of natural products. Chem. Rev. 2013, 113, 5595, DOI: 10.1021/cr400008h5chttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXltVWkurs%253D&md5=2b7c16be59e534fd93566c2bf96aa6b6Diastereoselective Allylation of Carbonyl Compounds and Imines: Application to the Synthesis of Natural ProductsYus, Miguel; Gonzalez-Gomez, Jose C.; Foubelo, FranciscoChemical Reviews (Washington, DC, United States) (2013), 113 (7), 5595-5698CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)A review. The goal of this review is to highlight diastereoselective allylations involving the use of chiral reagents, emphasizing recent developments of synthetic interest. The review is organized according to the source of stereocontrol. The last section of this review will be dedicated to related propargylation/allenylation processes, and to the application of these methodologies to some selected synthesis of natural products.
- 6(a) Matteson, D. S.; Ray, R. alpha-Chloro boronic esters from homologation of boronic esters. J. Am. Chem. Soc. 1980, 102, 7590, DOI: 10.1021/ja00545a0466ahttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL3MXjtV2nsg%253D%253D&md5=e91984e6c035eeadec90335d4401426cDirected chiral synthesis with pinanediol boronic estersMatteson, Donald S.; Ray, RahulJournal of the American Chemical Society (1980), 102 (25), 7590-1CODEN: JACSAT; ISSN:0002-7863.Homologation of boronic esters of (+)-I with LiCHCl2 gave S-α-chloroalkaneboronic esters with high stereoselectivity. Thus, homologation of II (R = Ph) to S-II (R = PhCHCl) which was treated with MeMgBr to give S-II (R = PhCHMe) which was oxidized to give 93.7% pure S-PhCHMeOH.(b) Matteson, D. S.; Sadhu, K. M.; Peterson, M. L. 99% Chirally selective synthesis via pinanediol boronic esters: insect pheromones, diols, and an amino alcohol. J. Am. Chem. Soc. 1986, 108, 810, DOI: 10.1021/ja00264a0396bhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL28Xht12ltLc%253D&md5=ddd2443cdd77f88e62de82fcd35f26e499% Chirally selective synthesis via pinanediol boronic esters: insect pheromones, diols, and an amino alcoholMatteson, Donald S.; Sadhu, Kizhakethil Mathew; Peterson, Mark L.Journal of the American Chemical Society (1986), 108 (4), 810-19CODEN: JACSAT; ISSN:0002-7863.Chiral selectivities exceed 99% in the homologation of (+)-pinanediol alkylboronates I (R = Bu, CH2CHMe2, CH2Ph) to (1S)-(1-chloroalkyl)boronates II by reaction of I with LiCHCl2 at -100° followed by ZnCl2-catalyzed rearrangement of the resulting borate complexes at 0-25°. Diastereoselectivity falls to 95.7% with I (R = Me). (-)-Pinanediol leads to the 1R-isomers. Nucleophilic displacements on II gave new chiral boronic esters which were homologated further. Compatible substituents include α- or β-benzyloxy, δ- or ε-ethylene ketal, β-tert-butoxycarbonyl, α-azido, and β-hexylthio. Three insect pheromones each contg. two chiral centers were prepd.: (3S,4S)-4-methyl-3-heptanol (elm bark beetle), exo-brevicomin (western pine beetle), and eldanolide (African sugar cane borer). Stereocontrolled syntheses also gave (5S,6S)-5,6-decanediol, (5S,6R,7S)-PhCH2OCHBuCHMeCHBuOH, and (5S,6S)-H2NCHBuCHBuOH.
- 7(a) Dale, J. A.; Mosher, H. S. Nuclear magnetic resonance enantiomer regents. Configurational correlations via nuclear magnetic resonance chemical shifts of diastereomeric mandelate, O-methylmandelate, and.alpha.-methoxy-.alpha.-trifluoromethylphenyl-acetate (MTPA) esters. J. Am. Chem. Soc. 1973, 95, 512, DOI: 10.1021/ja00783a0347ahttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaE3sXotlOjtw%253D%253D&md5=27a7f9c81b89c6b29ffed705dc4f689cNuclear magnetic resonance enantiomer regents. Configurational correlations via nuclear magnetic resonance chemical shifts of diastereomeric mandelate, O-methylmandelate, and α-methoxy-α-trifluoromethylphenylacetate (MTPA) estersDale, James A.; Mosher, Harry S.Journal of the American Chemical Society (1973), 95 (2), 512-19CODEN: JACSAT; ISSN:0002-7863.An empirically derived correlation of configuration and NMR chem. shifts for diastereomeric mandelate, O-methylmandelate and α-methoxy-α-trifluoromethylphenylacetate esters has been developed and rationalized in terms of useful models. These models have been successfully applied to over 40 examples. The correlations involve the relative chem. shifts of the proton resonances from the groups attached to the carbinyl carbon of these diastereomeric esters.(b) Ohtani, I.; Kusumi, T.; Kashman, Y.; Kakisawa, H. High-field FT NMR application of Mosher’s method. The absolute configurations of marine terpenoids. J. Am. Chem. Soc. 1991, 113, 4092, DOI: 10.1021/ja00011a0067bhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK3MXktV2jtL0%253D&md5=5dbc18835b60b35f283c7e04767bf238High-field FT NMR application of Mosher's method. The absolute configurations of marine terpenoidsOhtani, Ikuko; Kusumi, Takenori; Kashman, Yoel; Kakisawa, HiroshiJournal of the American Chemical Society (1991), 113 (11), 4092-6CODEN: JACSAT; ISSN:0002-7863.Mosher's (1H) method to elucidate the abs. configuration of marine secondary alcs. was reexamd. by high-field FT NMR spectroscopy, which enables assignment of most of the protons of complex mols. There is a systematic arrangement of Δδ (δS- δR) values obtained for the (R)- and (S)-MTPA (3,3,3-trifluoro-2-methoxy-2-phenylpropionic acid) esters of (-)-methanol, (-)-borneol, cholesterol, and ergosterol, whose abs. configurations are known. Anal. of the Δδ values of these compds. led to a rule which could predict the abs. configurations of natural products. When this rule was applied to marine terpenoids including cembranolides and xenicanes, their abs. configurations were assigned and a part of the results were confirmed by x-ray analyses. In the case of sipholenol A, which has a sterically hindered OH group, this rule is inapplicable. The problem is overcome by inverting the OH group to a less sterically hindered position; the resulting epimer gives systematically arranged Δδ values, which enabled the elucidation of the abs. configuration. Comparison of the present method with Mosher's 19F method indicates that the latter using 19F NMR lacks reliability, and that the abs. configurations of the natural products in the literature detd. by 19F NMR spectra of MTPA esters should all be reexamd.
- 8(a) Kennedy, J. W. J.; Hall, D. G. Dramatic rate enhancement with preservation of stereospecificity in the first metal-catalyzed additions of allylboronates. J. Am. Chem. Soc. 2002, 124, 11586, DOI: 10.1021/ja027453j8ahttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD38Xms12rtbw%253D&md5=b6d86454d242b814b07d1c1478a08ba7Dramatic Rate Enhancement with Preservation of Stereospecificity in the First Metal-Catalyzed Additions of AllylboronatesKennedy, Jason W. J.; Hall, Dennis G.Journal of the American Chemical Society (2002), 124 (39), 11586-11587CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The first example of Lewis acid-catalyzed addn. of allylboronates to aldehydes with preserving the stereochem., obsd. in uncatalyzed allylboration reactions, is reported. Thus, addn. of isomerically pure, tetrasubstituted 2-alkoxycarbonyl allylboronates I (R1 = Et, R2 = Me; R1 = Me, R2 = Bu) to aldehydes R3CHO (R3 = Bu, Me2CHCH2, cyclohexyl, Ph, 3-iodophenyl, C6F5, PhCH2CH2) in the presence of Sc(OTf)3, Cu(OTf)2, or Yb(OTf)3 yielded γ-lactones II in good yields at temps. almost 100° lower than those of the corresponding uncatalyzed reactions. The large rate enhancement over the uncatalyzed reaction provides a highly improved practical approach to access aldol-like adducts with a stereogenic quaternary carbon center. The crucial role of the 2-alkoxycarbonyl group on allylboronates I was demonstrated with control expts. using a model allylboronate lacking such an ester group.(b) Ishiyama, T.; Ahiko, T.; Miyaura, N. Acceleration effect of Lewis acid in allylboration of aldehydes: catalytic, regiospecific, diastereospecific, and enantioselective synthesis of homoallyl alcohols. J. Am. Chem. Soc. 2002, 124, 12414, DOI: 10.1021/ja02103458bhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD38XntlOrtL4%253D&md5=1bb4a36912a174f88840fc326b579ea2Acceleration Effect of Lewis Acid in Allylboration of Aldehydes: Catalytic, Regiospecific, Diastereospecific, and Enantioselective Synthesis of Homoallyl AlcoholsIshiyama, Tatsuo; Ahiko, Taka-aki; Miyaura, NorioJournal of the American Chemical Society (2002), 124 (42), 12414-12415CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The addn. of pinacol allylboronic esters to arom. and aliph. aldehydes smoothly occurred at -78° in toluene in the presence of a catalytic amt. of AlCl3 or Sc(OTf)3 (10 mol %) to give the corresponding homoallyl alcs. in high yields. The reactions proceeded regio- and diastereospecifically, yielding the isomerically pure syn- and anti-homoallyl alcs. from (Z)- and (E)-allylboronic esters, resp. The protocol was also applied to enantioselective reactions by using a chiral Lewis acid catalyst.
- 9(a) Peng, F.; Hall, D. G. Simple, stable, and versatile double-allylation reagents for the stereoselective preparation of skeletally diverse compounds. J. Am. Chem. Soc. 2007, 129, 3070, DOI: 10.1021/ja068985t9ahttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXhvFKqtLc%253D&md5=51fa6e04bf31cbde6eda770540aedc92Simple, Stable, and Versatile Double-Allylation Reagents for the Stereoselective Preparation of Skeletally Diverse CompoundsPeng, Feng; Hall, Dennis G.Journal of the American Chemical Society (2007), 129 (11), 3070-3071CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)A new and efficient class of double-allylation reagents, α-trimethylsilylmethyl allylboronate and the crotylboronates, is reported. These stable bimetallic reagents are prepd. easily in enantiomerically pure form and add under BF3 catalysis onto a wide range of aldehydes to afford a direct access to hydroxyl-functionalized allylic silanes, e.g., I, in very high E/Z selectivity and excellent enantioselectivity (up to 98% ee). The useful hydroxyl-functionalized allylsilane intermediates can be exploited in chemodivergent syntheses of various compd. classes such as acyclic propionate units, polysubstituted furans, vinylcyclopropanes, and larger carbocycles.(b) 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)-crotyl-boronate. Org. Lett. 2021, 23, 7808, DOI: 10.1021/acs.orglett.1c028319bhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXitFalurjO&md5=fdb7ef86f0e8aee51a6678cf54675bcaAsymmetric Syntheses of (E)-δ-Hydroxymethyl-anti-homoallylic Alcohols via Highly Enantio- and Stereoselective Aldehyde Allylation with α-Borylmethyl-(E)-crotylboronateLiu, Jiaming; Gao, Shang; Chen, MingOrganic 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.(c) Liu, J.; Chen, M. Highly stereoselective syntheses of (E)-δ-boryl-anti-homoallylic alcohols via allylation with α-boryl-(E)-crotylboronate. Chem. Commun. 2021, 57, 10799, DOI: 10.1039/D1CC04058H9chttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXitFGhs73I&md5=a37b079f4821d49e55d3acea2b683793Highly stereoselective syntheses of (E)-δ-boryl-anti-homoallylic alcohols via allylation with α-boryl-(E)-crotylboronateLiu, Jiaming; Chen, MingChemical Communications (Cambridge, United Kingdom) (2021), 57 (82), 10799-10802CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)A highly stereoselective synthesis of (E)-δ-boryl-anti-homoallylic alcs. is developed. In the presence of a Lewis acid, aldehyde allylation with α-boryl-(E)-crotylboronate gave δ-boryl-anti-homoallylic alcs. in good yields with excellent E-selectivity. The E-vinylboronate group in the products provides a useful handle for cross-coupling reactions as illustrated in the fragment synthesis of chaxamycins.
- 10(a) Jain, P.; Antilla, J. C. Chiral Brønsted acid-catalyzed allylboration of aldehydes. J. Am. Chem. Soc. 2010, 132, 11884, DOI: 10.1021/ja104956s10ahttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXpvVartLs%253D&md5=2e3c86159261a9773246329f11b2197cChiral Bronsted Acid-Catalyzed Allylboration of AldehydesJain, Pankaj; Antilla, Jon C.Journal of the American Chemical Society (2010), 132 (34), 11884-11886CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)A new high-yielding and highly enantioselective chiral Bronsted acid-catalyzed allylboration of aldehydes RCHO (R = Ph, 4-ClC6H4, PhCH2, cyclohexyl, 2-thienyl, 1-naphthyl, etc.) with allyl pinacol boronate is described. The reaction is shown to be highly general, with a broad substrate scope that covers aryl, heteroaryl, α,β-unsatd., and aliph. aldehydes. The reaction conditions are also shown to be effective for the catalytic enantioselective crotylation of aldehydes. The high reactivity of the allylboronate is suggested to be due to protonation of the boronate oxygen by the chiral phosphoric acid catalyst.(b) Miura, T.; Nishida, Y.; Morimoto, M.; Murakami, M. Enantioselective synthesis of anti-homoallylic alcohols from terminal alkynes and aldehydes based on concomitant use of a cationic iridium complex and a chiral phosphoric acid. J. Am. Chem. Soc. 2013, 135, 11497, DOI: 10.1021/ja405790t10bhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhtFOltrrK&md5=6ae6cf949e8df4b4f184d819d629d910Enantioselective Synthesis of Anti Homoallylic Alcohols from Terminal Alkynes and Aldehydes Based on Concomitant Use of a Cationic Iridium Complex and a Chiral Phosphoric AcidMiura, Tomoya; Nishida, Yui; Morimoto, Masao; Murakami, MasahiroJournal of the American Chemical Society (2013), 135 (31), 11497-11500CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)We report a highly diastereo- and enantioselective synthesis of anti homoallylic alcs. from terminal alkynes via (E)-1-alkenylboronates based upon two catalytic reactions: a cationic iridium complex-catalyzed olefin transposition of (E)-1-alkenylboronates and a chiral phosphoric acid-catalyzed allylation reaction of aldehydes.(c) Incerti-Pradillos, C. A.; Kabeshov, M. A.; Malkov, A. V. Highly stereoselective synthesis of Z-homoallylic alcohols by kinetic resolution of racemic secondary allyl boronates. Angew. Chem., Int. Ed. 2013, 52, 5338, DOI: 10.1002/anie.20130070910chttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXlslyru7c%253D&md5=fadea68f6a8dbc6cafee8139d5707145Highly Stereoselective Synthesis of Z-Homoallylic Alcohols by Kinetic Resolution of Racemic Secondary Allyl BoronatesIncerti-Pradillos, Celia A.; Kabeshov, Mikhail A.; Malkov, Andrei V.Angewandte Chemie, International Edition (2013), 52 (20), 5338-5341CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)In the presence of the bis(triisopropylphenyl)binaphthylphosphoric acid (R)-TRIP and benzoic acid in toluene, racemic secondary allyl pinacolboronates RCH[B(OCMe2CMe2O)]CH:CH2 (R = Me, n-Pr) underwent enantioselective addn. reactions to aldehydes R1CHO [R1 = Ph, (E)-PhCH:CH, PhCH2CH2, 4-MeOC6H4, 4-FC6H4, 4-ClC6H4, 2-naphthyl, 2-MeC6H4, 2-thienyl, 4-F3CC6H4, cyclohexyl] to give nonracemic (R,Z)-homoallylic alcs. RCH:CHCH2CH(OH)R1 [R = Me, n-Pr; R1 = Ph, (E)-PhCH:CH, PhCH2CH2, 4-MeOC6H4, 4-FC6H4, 4-ClC6H4, 2-naphthyl, 2-MeC6H4, 2-thienyl, 4-F3CC6H4, cyclohexyl] in 70-97% yields, 87-99% ee, and (in all but one case) > 25:1 Z:E stereoselectivity. Models for the transitions states of allylboronate addns. to aldehydes were studied computationally, indicating that increasing the size of the boronate ester substituent should increase the stereoselectivity for the (Z)-homoallylic alc. product.(d) Huang, Y.; Yang, X.; Lv, Z.; Cai, C.; Kai, C.; Pei, Y.; Feng, Y. Asymmetric synthesis of 1,3-butadienyl-2-carbinols by the homoallenylboration of aldehydes with a chiral phosphoric acid catalyst. Angew. Chem., Int. Ed. 2015, 54, 7299, DOI: 10.1002/anie.20150183210dhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXnsFymtb4%253D&md5=59a08e15a47eb04e2062baf0e9577d64Asymmetric Synthesis of 1,3-Butadienyl-2-carbinols by the Homoallenylboration of Aldehydes with a Chiral Phosphoric Acid CatalystHuang, Yiyong; Yang, Xing; Lv, Zongchao; Cai, Chen; Kai, Cheng; Pei, Yong; Feng, YuAngewandte Chemie, International Edition (2015), 54 (25), 7299-7302CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)Asym. C(sp)-C(sp2) bond formation to give enantiomerically enriched 1,3-butadienyl-2-carbinols occurred through a homoallenylboration reaction between a 2,3-dienylboronic ester and aldehydes under the catalysis of a chiral phosphoric acid (CPA). A diverse range of enantiomerically enriched butadiene-substituted secondary alcs. with aryl, heterocyclic, and aliph. substituents were synthesized in very high yield with high enantioselectivity. Preliminary d. functional theory (DFT) calcns. suggest that the reaction proceeds via a cyclic six-membered chairlike transition state with essential hydrogen-bond activation in the allene reagent. The catalytic reaction was amenable to the gram-scale synthesis of a chiral alkyl butadienyl adduct, which was converted into an interesting optically pure compd. bearing a benzo-fused spirocyclic cyclopentenone framework.(e) Gao, S.; Chen, M. Enantioselective syn- and anti-alkoxyallylation of aldehydes via Brønsted acid catalysis. Org. Lett. 2018, 20, 6174, DOI: 10.1021/acs.orglett.8b0265310ehttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhslyjsrfO&md5=5d1a235ebfc1ada813a3ff08d62ad1abEnantioselective syn- and anti-Alkoxyallylation of Aldehydes via Bronsted Acid CatalysisGao, Shang; Chen, MingOrganic Letters (2018), 20 (19), 6174-6177CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)A diastereo- and enantioselective alkoxyallylation via phosphoric acid catalysis was reported. Under the developed conditions, either 1,2-syn- or 1,2-anti-alkoxyallylation adducts were obtained in good yields with high enantioselectivities.(f) Gao, S.; Chen, M. Enantioselective syntheses of 1, 4-pentadien-3-yl carbinols via Brønsted acid catalysis. Org. Lett. 2020, 22, 400, DOI: 10.1021/acs.orglett.9b0408910fhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXisVCht73E&md5=1e532d5a996925a8534ebec8b010ecf2Enantioselective Syntheses of 1,4-Pentadien-3-yl Carbinols via Bronsted Acid CatalysisGao, Shang; Chen, MingOrganic Letters (2020), 22 (2), 400-404CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)An asym. addn. of substituted 1,3-pentadienylboronates to aldehydes via Bronsted acid catalysis is reported. Under the developed conditions, a variety of synthetically useful 1,4-pentadien-3-yl carbinols were obtained in good yields with high enantioselectivities in the presence of a catalytic amt. of a chiral phosphoric acid.(g) Liu, J.; Chen, M. Enantioselective anti- and syn-(borylmethyl)allylation of aldehydes via Brønsted acid catalysis. Org. Lett. 2020, 22, 8967, DOI: 10.1021/acs.orglett.0c0336610ghttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXit1arsb3F&md5=e7fd9832fa39259b1eb4e0c3eba0dc18Enantioselective anti- and syn-(Borylmethyl)allylation of Aldehydes via Bronsted Acid CatalysisLiu, Jiaming; Chen, MingOrganic Letters (2020), 22 (22), 8967-8972CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)The enantioselective anti- and syn-(borylmethyl)allylation of aldehydes via phosphoric acid catalysis is reported. Both (E)- and (Z)-γ-borylmethyl allylboronate reagents were prepd. via the Cu-catalyzed highly stereoselective protoboration of 1,3-dienylboronate. Chiral phosphoric acid-catalyzed aldehyde allylation with either the (E)- or (Z)-allylboron reagent provided 1,2-anti- or 1,2-syn-adducts in good yields with high enantioselectivities. The application to the synthesis of morinol D was accomplished.(h) 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, DOI: 10.1002/anie.20210700410hhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXit1SqsLjK&md5=625a2db91a0c47923f956ef8b6f73202Stereochemical Control via Chirality Pairing: Stereodivergent Syntheses of Enantioenriched Homoallylic AlcoholsGao, Shang; Duan, Meng; Liu, Jiaming; Yu, Peiyuan; Houk, Kendall N.; Chen, MingAngewandte 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.(i) 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, DOI: 10.1039/D1SC04047B10ihttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXitVKnurzI&md5=b0f8cb247ce1981632f7b782ec1f28daCatalytic asymmetric transformations of racemic α-borylmethyl-(E)-crotylboronate via kinetic resolution or enantioconvergent reaction pathwaysGao, Shang; Liu, Jiaming; Chen, MingChemical 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.(j) Gao, S.; Duan, M.; Andreola, L. R.; Yu, P.; Wheeler, S. E.; Houk, K. N.; Chen, M. Unusual enantiodivergence in chiral Brønsted acid-catalyzed asymmetric allylation with β-alkenyl allylic boronates. Angew. Chem., Int. Ed. 2022, 61, e202208908 DOI: 10.1002/anie.20220890810jhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB38XitlGlsL3P&md5=083d893b35c49dcdd026dcabdd1ca977Unusual Enantiodivergence in Chiral Broensted Acid-Catalyzed Asymmetric Allylation with β-Alkenyl Allylic BoronatesGao, Shang; Duan, Meng; Andreola, Laura R.; Yu, Peiyuan; Wheeler, Steven E.; Houk, Kendall N.; Chen, MingAngewandte Chemie, International Edition (2022), 61 (41), e202208908CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)A rare example of enantiodivergent aldehydes RCHO (R = Ph, naphthalen-2-yl, thiophen-3-yl, etc.) addn. with β-alkenyl allylic boronates CH2=CHC(=CH2)CH2R1 (R1 = 4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl, 4,4,5,5-tetrapropyl-1,3,2-dioxaborolan-2-yl, 4,4,6,6-tetramethyl-1,3,2-dioxaborinan-2-yl, etc.) via chiral Bronsted acid catalysis. 2,6-Di-9-anthracenyl-substituted chiral phosphoric acid-catalyzed asym. allylation using β-vinyl substituted allylic boronate that gave alcs. RCH(OH)CH2C(=CH2)CH=CH2 with R abs. configuration were reported. The sense of asym. induction of the catalyst in these reactions is opposite to those in prior reports. Moreover, in the presence of the same acid catalyst, the reactions with β-2-propenyl substituted allylic boronate CH3C(=CH2)C(=CH2)CH2Bpin generated homoallylic alc. products RCH(OH)CH2C(=CH2)C(=CH2)CH3 with S abs. configuration. Unusual substrate-catalyst C-H···π interactions in the favored reaction transition state were identified as the origins of obsd. enantiodivergence through DFT computational studies.
- 11(a) Jain, P.; Wang, H.; Houk, K. N.; Antilla, J. C. Brønsted acid catalyzed asymmetric propargylation of aldehydes. Angew. Chem., Int. Ed. 2012, 51, 1391, DOI: 10.1002/anie.20110740711ahttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhs12gtrrK&md5=1b78976d2d9f66826412e31f93bc7a71Bronsted acid-catalyzed asymmetric propargylation of aldehydesJain, Pankaj; Wang, Hao; Houk, Kendall N.; Antilla, Jon C.Angewandte Chemie, International Edition (2012), 51 (6), 1391-1394, S1391/1-S1391/41CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)A Bronsted acid-catalyzed propargylation of aldehydes with allenylboronate is described. Corresponding homopropargylic alcs. were obtained using this methods.(b) Reddy, L. R. Chiral Brønsted acid catalyzed enantioselective propargylation of aldehydes with allenylboronate. Org. Lett. 2012, 14, 1142, DOI: 10.1021/ol300075n11bhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhtFWhtrs%253D&md5=ab409111adb135d67f255c4e7cb51a0eChiral Bronsted Acid Catalyzed Enantioselective Propargylation of Aldehydes with AllenylboronateReddy, Leleti RajenderOrganic Letters (2012), 14 (4), 1142-1145CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)A highly enantioselective chiral Bronsted acid-catalyzed propargylation of aldehydes with allenylboronate is described. The reaction is shown to be practical and quite general with a broad substrate scope covering aryl, polyaryl, heteroaryl, α,β-unsatd., and aliph. aldehydes.(c) Chen, M.; Roush, W. R. Enantioselective synthesis of anti- and syn-homopropargyl alcohols via chiral Brønsted acid catalyzed asymmetric allenylboration reactions. J. Am. Chem. Soc. 2012, 134, 10947, DOI: 10.1021/ja303146711chttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XptFWjt74%253D&md5=847f94eab34fdcbd6e7de9d05e14d2b4Enantioselective Synthesis of anti- and syn-Homopropargyl Alcohols via Chiral Bronsted Acid Catalyzed Asymmetric Allenylboration ReactionsChen, Ming; Roush, William R.Journal of the American Chemical Society (2012), 134 (26), 10947-10952CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Chiral Bronsted acid catalyzed asym. allenylboration reactions are described. Under optimized conditions, anti-homopropargyl alcs. are obtained in high yields with excellent diastereo- and enantioselectivities from stereochem. matched aldehyde allenylboration reactions with chiral allenylboronate catalyzed by the chiral phosphoric acid. The syn-isomers can also be obtained in good diastereoselectivities and excellent enantioselectivities from the mismatched allenylboration reactions of arom. aldehydes using allenylboronate in the presence of the enantiomeric phosphoric acid. The stereochem. of the Me group introduced into syn- and anti-homopropargyl alcs. is controlled by the chirality of the allenylboronate, whereas the configuration of the new hydroxyl stereocenter is controlled by the enantioselectivity of the chiral phosphoric acid catalyst used in these reactions. The synthetic utility of this methodol. was further demonstrated in highly diastereoselective syntheses of a variety of anti, anti-stereotriads, the direct synthesis of which has constituted a significant challenge using previous generations of aldol and crotylmetal reagents.(d) Tsai, A. S.; Chen, M.; Roush, W. R. Chiral Brønsted acid catalyzed enantioselective synthesis of anti-homopropargyl alcohols via kinetic resolution-aldehyde allenylboration using racemic allenylboronates. Org. Lett. 2013, 15, 1568, DOI: 10.1021/ol400345911dhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXjvVahtLw%253D&md5=ca86e207c376ddeda7cc13195cdfcaeeChiral Bronsted acid catalyzed enantioselective synthesis of anti-homopropargyl alcohols via kinetic resolution-aldehyde allenylboration using racemic allenylboronatesTsai, Andy S.; Chen, Ming; Roush, William R.Organic Letters (2013), 15 (7), 1568-1571CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)A chiral phosphoric acid catalyzed kinetic resoln./allenylboration of racemic allenylboronates with aldehydes is described. Allenylboration of aldehydes with 2.8 equiv of allenylboronate (±)-1 in the presence of 10 mol % of catalyst (R)-2 provided anti-homopropargyl alcs. 3 in 83-95% yield with 9:1 to 20:1 diastereoselectivity and 73-95% ee. The catalyst enables the kinetic resoln. of the racemic allenylboronate (±)-1 to set the Me stereocenter and biases the facial attack of the aldehyde to set the stereochem. of the hydroxyl group in 3.(e) Wang, M.; Khan, S.; Miliordos, E.; Chen, M. Enantioselective syntheses of homopropargylic alcohols via asymmetric allenylboration. Org. Lett. 2018, 20, 3810, DOI: 10.1021/acs.orglett.8b0139911ehttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhtFWhurfJ&md5=71d97280faed42ec95483f578268b963Enantioselective Syntheses of Homopropargylic Alcohols via Asymmetric AllenylborationWang, Mengzhou; Khan, Shahriar; Miliordos, Evangelos; Chen, MingOrganic Letters (2018), 20 (13), 3810-3814CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)A chiral phosphoric acid catalyzed allenylboration reaction is reported. Homopropargyl alcs. with an internal alkyne unit were obtained in good yields with high enantioselectivities under the developed conditions.
- 12(a) Reddy, L. R. Chiral Brønsted acid catalyzed enantioselective allenylation of aldehydes. Chem. Commun. 2012, 48, 9189, DOI: 10.1039/c2cc34371a12ahttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38Xht1ajtL7F&md5=008740ed161f5d0a970e145a83fa4e28Chiral Bronsted acid catalyzed enantioselective allenylation of aldehydesReddy, Leleti RajenderChemical Communications (Cambridge, United Kingdom) (2012), 48 (73), 9189-9191CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)A versatile and highly enantioselective chiral Bronsted acid-catalyzed allenylation of aldehydes with propargyl borolane is reported. The reaction is shown to be practical and quite general with a broad substrate scope covering aryl, heteroaryl, α,β-unsatd., and aliph. aldehydes.(b) Wang, M.; Khan, S.; Miliordos, E.; Chen, M. Enantioselective allenylation of aldehydes via Brønsted acid catalysis. Adv. Synth. Catal. 2018, 360, 4634, DOI: 10.1002/adsc.20180108012bhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXitVGlt7vF&md5=7bb7f588294d755d860a684bd7f430d1Enantioselective Allenylation of Aldehydes via Bronsted Acid CatalysisWang, Mengzhou; Khan, Shahriar; Miliordos, Evangelos; Chen, MingAdvanced Synthesis & Catalysis (2018), 360 (23), 4634-4639CODEN: ASCAF7; ISSN:1615-4150. (Wiley-VCH Verlag GmbH & Co. KGaA)An enantioselective allenylation of aldehydes catalyzed by a chiral, nonracemic phosphoric acid was reported. Under the developed conditions, 1,1'-disubstituted allenic alcs. were obtained in 64-98% yields with 88-99% ee. Computational studies were conducted to probe the origin of asym. induction. Mechanistic studies suggest that the pinacol moiety of the propargylboronate is crit. to the enantioselectivity of the reaction that was supported by exptl. data.
- 13(a) Grayson, M. N.; Pellegrinet, S. C.; Goodman, J. M. Mechanistic insights into the BINOL-derived phosphoric acid-catalyzed asymmetric allylboration of aldehydes. J. Am. Chem. Soc. 2012, 134, 2716, DOI: 10.1021/ja210200d13ahttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XlvFaq&md5=4eac2953c47f8bb50d6e44c6ce899216Mechanistic Insights into the BINOL-Derived Phosphoric Acid-Catalyzed Asymmetric Allylboration of AldehydesGrayson, Matthew N.; Pellegrinet, Silvina C.; Goodman, Jonathan M.Journal of the American Chemical Society (2012), 134 (5), 2716-2722CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)BINOL-derived phosphoric acids catalyze the asym. allylboration of aldehydes. DFT and QM/MM hybrid calcns. showed that the reaction proceeds via a transition state involving both a hydrogen-bonding interaction from the catalyst hydroxyl group to the pseudoaxial oxygen of the cyclic boronate and a stabilizing interaction from the phosphoryl oxygen of the catalyst to the formyl hydrogen of the aldehyde. These interactions lower the energy of the transition structure and provide extra rigidity to the system. This mechanistic pathway is consistent with the exptl. obsd. enantioselectivity except in one case. We have used our model's predictions to guide our own exptl. work. The conflict is resolved in favor of our calcns.(b) Wang, H.; Jain, P.; Antilla, J. C.; Houk, K. N. Origins of stereoselectivities in chiral phosphoric acid catalyzed allylborations and propargylations of aldehydes. J. Org. Chem. 2013, 78, 1208, DOI: 10.1021/jo302787m13bhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXkt1ygtg%253D%253D&md5=075199c52693806970b3f61952f1e8baOrigins of Stereoselectivities in Chiral Phosphoric Acid Catalyzed Allylborations and Propargylations of AldehydesWang, Hao; Jain, Pankaj; Antilla, Jon C.; Houk, K. N.Journal of Organic Chemistry (2013), 78 (3), 1208-1215CODEN: JOCEAH; ISSN:0022-3263. (American Chemical Society)The chiral BINOL-H3PO4 catalyzed allylboration and propargylation reactions were studied with d. functional theory (B3LYP and B3LYP-D3). Two different models were recently proposed for these reactions by Goodman and the authors' group, resp. In Goodman's model for allylborations, the catalyst interacts with the boronate pseudoaxial oxygen. By contrast, the authors' model for propargylations predicts that the catalyst interacts with the boronate pseudoequatorial oxygen. In both models, the H3PO4 stabilizes the transition state by forming a strong H bond with the oxygen of the boronate and is oriented by a formyl H bond (Goodman model) and by other electrostatic attractions in the authors' model. Both of these models have now been restudied for both allylborations and propargylations. For the most effective catalyst for these reactions, the lowest energy transition state corresponds to Goodman's axial model, while the best transition state leading to the minor enantiomer involves the equatorial model. The high enantioselectivity obsd. with only the bulkiest catalyst arises from the steric interactions between the substrates and the bulky groups on the catalyst, and the resulting necessity for distortion of the catalyst in the disfavored transition state.(c) Grayson, M. N.; Goodman, J. M. Understanding the mechanism of the asymmetric propargylation of aldehydes promoted by 1,1’-bi-2-naphthol-derived catalysts. J. Am. Chem. Soc. 2013, 135, 6142, DOI: 10.1021/ja312213713chttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXksFSktL8%253D&md5=62409c6d798dba54a22550abb62082f9Understanding the Mechanism of the Asymmetric Propargylation of Aldehydes Promoted by 1,1'-Bi-2-naphthol-Derived CatalystsGrayson, Matthew N.; Goodman, Jonathan M.Journal of the American Chemical Society (2013), 135 (16), 6142-6148CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)1,1'-Bi-2-naphthol (BINOL)-derived phosphoric acids catalyze the asym. propargylation of aldehydes. D. functional theory (DFT) calcns. showed that the reaction proceeds via a six-membered transition structure (TS) in which the catalyst Bronsted acidic site interacts with the pseudoaxial cyclic boronate oxygen and the phosphoryl oxygen interacts with the formyl proton. This model accurately predicts the stereochem. outcome obsd. exptl. Replacement of the phosphoric acid hydroxyl group with an N-triflyl moiety has been included in the model by calcn. and a broader understanding achieved by qual. assessment of similar reactions. We present a qual. guide to rationalizing the exptl. outcome and use this to make a prediction which was confirmed exptl.
- 14(a) Miura, T.; Nakahashi, J.; Zhou, W.; Shiratori, Y.; Stewart, S. G.; Murakami, M. Enantioselective synthesis of anti-1,2-oxaborinan-3-enes from aldehydes and 1,1-di(boryl)alk-3-enes using ruthenium and chiral phosphoric acid catalysts. J. Am. Chem. Soc. 2017, 139, 10903, DOI: 10.1021/jacs.7b0640814ahttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhtFOmtrnF&md5=9c4c524e47036cc592bd48da72691167Enantioselective Synthesis of anti-1,2-Oxaborinan-3-enes from Aldehydes and 1,1-Di(boryl)alk-3-enes Using Ruthenium and Chiral Phosphoric Acid CatalystsMiura, Tomoya; Nakahashi, Junki; Zhou, Wang; Shiratori, Yota; Stewart, Scott G.; Murakami, MasahiroJournal of the American Chemical Society (2017), 139 (31), 10903-10908CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)A cationic Ru(II) complex catalyzes double-bond transposition of 1,1-di(boryl)alk-3-enes to generate in situ 1,1-di(boryl)alk-2-enes, which then undergo chiral H3PO4 catalyzed allylation of aldehydes producing homoallylic alcs. with a (Z)-vinylboronate moiety. 1,2-Anti stereochem. is installed in an enantioselective manner. The (Z)-geometry forged in the products allows their isolation in a form of 1,2-oxaborinan-3-enes, upon which further synthetic transformations are operated.(b) Miura, T.; Oku, N.; Murakami, M. Diastereo- and enantioselective synthesis of (E)-δ-boryl-substituted anti-homoallylic alcohols in two steps from terminal alkynes. Angew. Chem., Int. Ed. 2019, 58, 14620, DOI: 10.1002/anie.20190829914bhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhs12jurrO&md5=e8959ffe827ecca629f3c0030547c3a5Diastereo- and Enantioselective Synthesis of (E)-δ-Boryl-Substituted anti-Homoallylic Alcohols in Two Steps from Terminal AlkynesMiura, Tomoya; Oku, Naoki; Murakami, MasahiroAngewandte Chemie, International Edition (2019), 58 (41), 14620-14624CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)The authors report the highly diastereo- and enantioselective prepn. of (E)-δ-boryl-substituted anti-homoallylic alcs. in two steps from terminal alkynes. This method consists of a Co(II)-catalyzed 1,1-diboration reaction of terminal alkynes with B2pin2 and a Pd(I)-mediated asym. allylation reaction of the resulting 1,1-di(boryl)alk-1-enes with aldehydes in the presence of a chiral H3PO4. Propyne, which is produced as the byproduct during petroleum refining, could be used as the starting material to construct homoallylic alcs. that are otherwise difficult to synthesize with high stereocontrol.(c) Gao, S.; Duan, M.; Houk, K. N.; Chen, M. Chiral phosphoric acid dual-function catalysis: asymmetric allylation with α-vinyl allylboron reagents. Angew. Chem., Int. Ed. 2020, 59, 10540, DOI: 10.1002/anie.20200003914chttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXnslGmtrw%253D&md5=47fc81077bc5b2e362c89d70d485267bChiral Phosphoric Acid Dual-Function Catalysis: Asymmetric Allylation with α-Vinyl Allylboron ReagentsGao, Shang; Duan, Meng; Houk, Kendall N.; Chen, MingAngewandte Chemie, International Edition (2020), 59 (26), 10540-10548CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)We report a dual function asym. catalysis by a chiral phosphoric acid catalyst that controls both enantioselective addn. of an achiral α-vinyl allylboronate to aldehydes and pseudo-axial orientation of the α-vinyl group in the transition state. The reaction produces dienyl homoallylic alcs. with high Z-selectivities and enantioselectivities. Computational studies revealed that minimization of steric interactions between the alkyl groups of the diol on boron and the chiral phosphoric acid catalyst influence the orientation of α-vinyl substituent of the allylboronate reagent to occupy a pseudo-axial position in the transition state.(d) Gao, S.; Duan, M.; Shao, Q.; Houk, K. N.; Chen, M. Development of α, α-disubstituted crotylboronate reagents and stereoselective crotylation via Brønsted or Lewis acid catalysis. J. Am. Chem. Soc. 2020, 142, 18355, DOI: 10.1021/jacs.0c0410714dhttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXitVGlu73I&md5=23e4240177bfd3e62da15f93fff04a3aDevelopment of α,α-Disubstituted Crotylboronate Reagents and Stereoselective Crotylation via Bronsted or Lewis Acid CatalysisGao, Shang; Duan, Meng; Shao, Qianzhen; Houk, K. N.; Chen, MingJournal of the American Chemical Society (2020), 142 (43), 18355-18368CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The development of α,α-disubstituted crotylboronate reagents is reported. Chiral Bronsted acid-catalyzed asym. aldehyde addn. with the developed E-crotylboron reagent gave (E)-anti-1,2-oxaborinan-3-enes with excellent enantioselectivities and E-selectivities. With BF3·OEt2 catalysis, the stereoselectivity is reversed, and (Z)-δ-boryl-anti-homoallylic alcs. were obtained with excellent Z-selectivities from the same E-crotylboron reagent. The Z-crotylboron reagent also participates in BF3·OEt2-catalyzed crotylation to furnish (Z)-δ-boryl-syn-homoallylic alcs. with good Z-selectivities. DFT computations establish the origins of obsd. enantio- and stereoselectivities of chiral Bronsted acid-catalyzed asym. allylation. Stereochem. models for BF3·OEt2-catalyzed reactions probably rationalize the Z-selective allyl addns. These reactions generate highly valuable homoallylic alc. products with a stereodefined trisubstituted alkene unit. The synthetic utility is further demonstrated by the total syntheses of salinipyrones A and B.(e) Chen, J.; Chen, M. Enantioselective syntheses of (Z)-6′-boryl-anti-1,2-oxaborinan-3-enes via a dienylboronate protoboration and asymmetric allylation reaction sequence. Org. Lett. 2020, 22, 7321, DOI: 10.1021/acs.orglett.0c0265714ehttps://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXhslOitr3I&md5=3f32fbff9243342497f55eff5ae0c2b8Enantioselective Syntheses of (Z)-6'-Boryl-anti-1,2-oxaborinan-3-enes via a Dienylboronate Protoboration and Asymmetric Allylation Reaction SequenceChen, Jichao; Chen, MingOrganic Letters (2020), 22 (18), 7321-7326CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)Asym. allylboration of aldehydes RCHO with allyltriboronate pinBCH2CH:CHCH(Bpin)2 afforded chiral 1,2-oxaborinanes I. Enantioselective synthesis of 6'-boryl-anti-1,2-oxaborinan-3-enes is reported. A Cu-catalyzed highly stereoselective 1,4-protoboration of 1,1-bisboryl-1,3-butadiene is developed to generate (E)-α,δ-bisboryl-crotylboronate. Chiral phosphoric acid-catalyzed asym. allylboration of aldehydes with the boron reagent produces 6'-boryl-anti-1,2-oxaborinan-3-enes with excellent Z-selectivities and enantioselectivities. The product contains a vinyl and alkyl boronate unit that can directly participate in a variety of subsequent transformations.(f) Zhang, Z.; Liu, J.; Gao, S.; Su, B.; Chen, M. Highly stereoselective syntheses of α,α-disubstituted (E)- and (Z)-crotylboronates. J. Org. Chem. 2023, 88, 3288, DOI: 10.1021/acs.joc.2c02606There is no corresponding record for this reference.
- 15Hoffmann, R. W. Allylic 1,3-strain as a controlling factor in stereoselective transformations. Chem. Rev. 1989, 89, 1841, DOI: 10.1021/cr00098a00915https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL1MXmtlWnurc%253D&md5=91540e91c0c31a112831dd5ac9d73f4dAllylic 1,3-strain as a controlling factor in stereoselective transformationsHoffmann, Reinhard W.Chemical Reviews (Washington, DC, United States) (1989), 89 (8), 1841-60CODEN: CHREAY; ISSN:0009-2665.A review with 155 refs. on the manifestation of allylic strain in the stereochem. of a host of chem. reactions, including cyclizations, intermol. addn., hydrogenation, cyclopropanation, and others.
Supporting Information
Supporting Information
The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.orglett.4c04663.
Experimental procedures, spectra for all new compounds (PDF)
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