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LetterAugust 19, 2020

Ru₃(CO)₁₂-Catalyzed Reaction of 1,6-Diynes, Carbon Monoxide, and Water via the Reductive Coupling of Carbon Monoxide
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Cathleen M. Crudden*
Cathleen M. Crudden
Department of Chemistry, Queen’s University, Chernoff Hall, Kingston, Ontario K7L 3N6, Canada
Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Chikusa, Nagoya 464-8601, Japan
*Email: [email protected]
More by Cathleen M. Crudden
http://orcid.org/0000-0003-2154-8107
Yuuki Maekawa
Yuuki Maekawa
Department of Chemistry, Queen’s University, Chernoff Hall, Kingston, Ontario K7L 3N6, Canada
Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Chikusa, Nagoya 464-8601, Japan
More by Yuuki Maekawa
Joshua J. Clarke
Joshua J. Clarke
Department of Chemistry, Queen’s University, Chernoff Hall, Kingston, Ontario K7L 3N6, Canada
More by Joshua J. Clarke
Tomohide Ida
Tomohide Ida
Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
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Yoshiya Fukumoto
Yoshiya Fukumoto
Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
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http://orcid.org/0000-0003-1064-0354
Naoto Chatani*
Naoto Chatani
Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
*Email: [email protected]
More by Naoto Chatani
http://orcid.org/0000-0001-8330-7478
Shinji Murai*
Shinji Murai
Nara Institute of Science and Technology, Ikoma, Nara 630-0192, Japan
*Email: [email protected]
More by Shinji Murai

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Organic Letters

Cite this: Org. Lett. 2020, 22, 22, 8747–8751

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https://doi.org/10.1021/acs.orglett.0c02349

Published August 19, 2020

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Abstract

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We report the ruthenium-catalyzed cyclization of 1,6-diynes with two molecules of carbon monoxide and water to give a variety of catechols. This reaction likely proceeds through the intermediacy of the water–gas shift reaction to generate an yne–diol-type intermediate followed by a [4 + 2] cycloaddition with 1,6-diynes. The reaction requires no external reductants or hydride sources and provides a novel and valuable method for the synthesis of a variety of catechols.

Subjects

The water–gas shift (WGS) reaction is a crucial industrial process for the production of high purity hydrogen gas from carbon monoxide (CO) and water. Metal dihydrides (I) are key intermediates (Scheme 1A). (1) The WGS reaction has been also applied in hydrogenation reactions as well as catalytic reactions for the regeneration of active catalytic species; (2) however, its use in organic synthesis remains underdeveloped.

Scheme 1. Water–Gas Shift Reaction for the Synthesis of Catechols from 1,6-Diynes

Our group previously reported that 1,6-diynes react with carbon monoxide and hydrosilane in the presence of simple Ru catalysts to provide catechol derivatives (Scheme 1B). (3) This reaction is proposed to proceed via a unique 1,3-shift of the silyl group in complex II to the oxygen atom of a coordinated CO. (4) Reaction of the resulting silyloxycarbyne complex III with a second molecule of CO gives dioxyacetylene IV. (5) This species can be trapped by cycloaddition with diynes 1, (6) yielding monosilylated catechols 2-Si (Scheme 1B). We speculated that this reaction might be carried out under WGS conditions if metal dihydride I could be considered a surrogate for II.

The use of metal catalysts to affect the cycloaddition of alkynes and diynes with a variety of partners, including other alkynes, alkenes, carbon dioxide, and nitriles, has become a topic of intense interest. (7) However, the synthesis of catechols through this type of cycloaddition has not been reported, even though early transition metals have been shown to affect the reductive coupling of CO to yield disiloxyethylenes under stoichiometric conditions. (8) Other examples where two molecules of CO are incorporated result in the preparation of 1,4-benzoquinones or 1,4-hydroquinones and thus do not proceed through the intermediacy of dihydroxyethyne. (9) Interestingly, despite their well-documented use in metathesis reactions and stoichiometric organometallic chemistry, (10a,b) metal carbyne species are scarcely invoked in catalytic transformations. (10c,d)

Herein, we report a novel, scalable synthesis of catechols through the intermediacy of a WGS reaction, where water is employed as the source of hydrogen, via metal carbynes as likely intermediates (Scheme 1C).

To optimize the reaction, we began with substrate 1a, which is predisposed toward cyclization because of the Thorpe–Ingold effect introduced by the geminal ester substituents. Reaction between 1a and carbon monoxide was carried out in a stainless steel autoclave employing 50 atm of CO and a polar solvent to which several equivalents of water was added. Ru₃(CO)₁₂ was employed as the catalyst at 2 mol % loading and the reaction carried out at 140 °C for 20 h. Under these conditions, the desired product (2a) was isolated after trituration in 81% yield (Table 1, entry 1).

Table 1. Optimization of Reaction Conditions for Cycloaddition of 1,6-Diyne 1a

entry	catalyst	H₂O (equiv)	solvent	yield (%)
1	Ru₃(CO)₁₂	4	1,4-dioxane	81
2	Ru₃(CO)₁₂	5	1,4-dioxane	70
3	Ru₃(CO)₁₂	2	1,4-dioxane	51
4^a	Ru₃(CO)₁₂	4	1,4-dioxane	61
5^b	Ru₃(CO)₁₂	4	1,4-dioxane	24
6	Fe₃(CO)₁₂	4	1,4-dioxane	0
7	Os₃(CO)₁₂	4	1,4-dioxane	0
8	Ru₃(CO)₁₂	4	CH₃CN	79
9	Ru₃(CO)₁₂	4	THF	81
10	Ru₃(CO)₁₂	4	CH₂Cl₂	46
11	Ru₃(CO)₁₂	4	toluene	38
12	Ru₃(CO)₁₂	4	CH₃OH	51

^{^a}

CO pressure: 30 bar.

^{^b}

Reaction temperature:120 °C.

Using larger or smaller amounts of water gave decreased yields of product 2a (70% yield for 15 mmol of H₂O and 51% yield for 6 mmol of H₂O, entries 2 and 3). Decreasing the CO pressure also led to lower product yields (30 atm of CO gave 61% yield) as did lower temperatures (24% yield at 120 °C) (entries 4 and 5). Using Fe₃(CO)₁₂ or Os₃(CO)₁₂ as the catalyst in place of Ru₃(CO)₁₂ gave no reaction (entries 6 and 7). The reaction was tolerant to other solvents such as CH₃CN (79%) and THF (81%); however, lower yields were obtained in CH₂Cl₂ (46%), toluene (38%), and CH₃OH (51%) (entries 8–12).

These optimized conditions (Table 1, entry 1) were then applied to a variety of diyne substrates (Table 2). Gratifyingly, the cycloaddition reaction did not require geminal substitution on the diyne, with the simple 1,6-heptadiyne (1b) reacting to give catechol 2b in 59% yield. Oxygen or nitrogen substitution in the tether as in 1c and 1d were well tolerated as was the ketone in 1e, yielding catechols 2c–2e. However, 1,7-heptadiyne (1f), which would yield the tetrahydronaphthalene structure, gave a complex mixture of products as did the related ether 1g, illustrating the importance of the fused 5/6 ring.

Table 2. Reaction of Terminal Alkynes with CO and H₂O in the Presence of Ru₃(CO)₁₂^a

^{^a}

Yields reported for isolated products.

Internal alkynes could also be employed as shown in Table 3. Diynes bearing a single substituent at the acetylenic terminus (methyl, 1h, or phenyl, 1j) gave adducts 2h and 2j in good yields, although terminal ethyl ester-substituted diyne 1i reacted with much lower efficiency. Disubstituted diynes 1k and 1l reacted smoothly to afford the corresponding hexasubstituted catechols 2k and 2l; however, diphenyl derivative 1m gave none of the desired product.

Table 3. Reaction of Internal Alkynes with CO and H₂O in the Presence of Ru₃(CO)₁₂^a

^{^a}

Yields reported for isolated products. ¹H NMR yields are shown in parentheses (1,3,5-trimethoxybenzene was used as an internal standard).

^{^b}

With 6 mol % of Ru₃(CO)₁₂.

Although identifiable byproducts were rarely observed, a side product from the reaction of diphenyl diyne 1m was instructive. Instead of the desired catechol, cyclopentadieneone–Ru complex 3m was isolated. This species results from incorporation of a single molecule of carbon monoxide in a well-precedented [2 + 2 + 1] cycloaddition, with Ru(CO)₃ binding to the cyclopentadieneone unit. (11) This compound was isolated in 89% yield relative to the added ruthenium catalyst (Scheme 2), and its structure was confirmed spectroscopically and by X-ray crystallography (Figure 1). The observation of compound 3m suggests that the [2 + 2 + 1] cycloaddition reaction is less sensitive to steric constraints than the desired [2 + 2 + 2] and that, once formed, these adducts can serve as catalyst sinks halting further transformations. Previous studies of Ru-catalyzed cycloadditions of diynes have documented the observation of related compounds, especially with sterically hindered diynes. (12)

Figure 1. Single-crystal X-ray structure of compound 3m (Ru, green; C, gray; O, red). Thermal elipsoids are shown at 50% probability. Selected bond lengths (Å) and angles [degs]: avg Ru–C_(C≡O) = 1.936(2); avg C–O_(C≡O) = 1.130(2); avg C_(C≡O)–Ru–C_(C≡O) = 94.86(7).

The catechol synthesis was also attempted employing alkyne 1n, which contains a terminal nitrile, since a successful cycloaddition would yield a pyridone product. Unfortunately, conditions were not found to affect pyridone synthesis, although product 2n was observed in small amounts along with other unidentified products (Scheme 3). Since catechol 2n was presumably produced by an unprecedented intermolecular cycloaddition, we also examined the reaction of phenyl acetylene; however, none of the desired product was observed from this alkyne.

Scheme 3. Reaction of Alkyne Bearing a Terminal Nitrile

From a mechanistic point of view, the use of water in place of hydrosilane is somewhat remarkable since these two reagents are at different oxidation states. As noted in the introduction, the most reasonable suggestion for the observed product is that metal hydrides are generated in situ via the water gas shift reaction (Scheme 4). (1) Isomerization of the proposed intermediate metal carbonyl dihydride via a 1,3-metal hydride shift gives hydroxycarbyne metal complex 4. The suggested 1,3-hydride shift (Scheme 4) is proposed on the basis of precedent from related silyl systems (4) and considerable other literature describing the intermediacy of hydroxy carbynes such as 4 as an alternative to the less stable formyl tautomers. (13) Reaction of this species with another molecule of carbon monoxide would result in yne–-diol metal complex 6 via a metallacyclopropenone 5 in analogy with similar reactivity seen in other metal complexes. (5,14)

The feasibility of yne–diol complex 6 is supported by reactions of related hydrosilanes performed in the absence of the 1,6-diyne (Scheme 5). (15) We previously reported that the Rh-catalyzed reaction between CO and a hydrosilane gives ene–diol 8, presumably derived from metal ene-silanol derivative 7. The stereochemistry of the ene-silanol 8 was shown to be cis, as expected for the mechanism shown.

Scheme 5. Formation of Ene–Diol in the Absence of Diene

In conclusion, we have developed a ruthenium-catalyzed catechol synthesis from a variety of diynes utilizing the WGS reaction to generate 1,2-hydroxyethyne from two molecules of CO and water. Reactions proceeding via metal carbyne complexes remain under represented in catalytic transformations. In this context, it is noteworthy that formation of a metal oxy–acetylene complex from a metal carbyne, carbon monoxide, and hydrogen is a likely pathway for the transformations described. Efforts to expand the synthetic applicability of this unique reactive intermediate are in progress.

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Author Information

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Corresponding Authors
- Cathleen M. Crudden - Department of Chemistry, Queen’s University, Chernoff Hall, Kingston, Ontario K7L 3N6, Canada; Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Chikusa, Nagoya 464-8601, Japan; http://orcid.org/0000-0003-2154-8107; Email: [email protected]
- Naoto Chatani - Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan; http://orcid.org/0000-0001-8330-7478; Email: [email protected]
- Shinji Murai - Nara Institute of Science and Technology, Ikoma, Nara 630-0192, Japan; Email: [email protected]
Authors
- Yuuki Maekawa - Department of Chemistry, Queen’s University, Chernoff Hall, Kingston, Ontario K7L 3N6, Canada; Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Chikusa, Nagoya 464-8601, Japan
- Joshua J. Clarke - Department of Chemistry, Queen’s University, Chernoff Hall, Kingston, Ontario K7L 3N6, Canada
- Tomohide Ida - Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
- Yoshiya Fukumoto - Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan; http://orcid.org/0000-0003-1064-0354
Notes
The authors declare no competing financial interest.

Acknowledgments

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We acknowledge the Natural Sciences and Engineering Research Council of Canada (NSERC) and the Canada Foundation for Innovation (CFI) for funding of the work from this lab as described in this article. Y.M. is a recipient of a JSPS postdoctoral fellowship. JSPS and NU are acknowledged for funding of this research through the World Premier International Research Center Initiative (WPI) program. This work was partially supported by a Grant in Aid for Specially Promoted Research by MEXT (No. 17H06091).

References

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This article references 15 other publications.

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5b
Transformation of a tungsten(0) alkyne to a tungsten(II) alkyne via vinylidene, carbyne, and ketenyl ligands
Birdwhistell, K. R.; Tonker, T. L.; Templeton, J. L.; Kenan, W. R., Jr.
Journal of the American Chemical Society (1985), 107 (15), 4474-83CODEN: JACSAT; ISSN:0002-7863.
Rearrangement of the W(0) d6 η2-alkyne complex fac-(dppe)(OC)3W(η2-PhC≡CH) (dppe = Ph2PCH2CH2PPh2) yields a meridional tricarbonyltungsten vinylidene complex, mer-(dppe)(OC)3W:C:CHPh, which provides an M-C-C framework for further ligand-based transformations. Electrophilic addn. at the β-C atom of the vinylidene ligand generates a cationic W carbyne, [mer-(dppe)(CO)3W≡CCH2Ph][BF4]. This carbyne cation undergoes CO substitution by Cl-, Br- and iodide, and in the absence of added ligand thermal dissocn. of CO it allows isolation of the highly electrophilic [(dppe)(OC)2W≡CCH2Ph][BF4] complex. This reagent adds F- to form a trans-FW≡CCH2Ph unit in (dppe)(OC)2FW≡CCH2Ph and also adds neutral ligands to form cationic dicarbonyl derivs., [(dppe)(OC)2LW≡CCH2Ph][BF4] (L = PMe3, MeCOMe, H2O). Addn. of dithiocarbamate salts -S2CNR2 (R = Me, Et) to the electrophilic dicarbonyl cation initially forms an η1-S2CNR2 adduct, which leads to coupling of carbyne and CO ligands to form an η2-ketenyl complex upon chelation of the dithiocarbamate ligand. Addn. of H+ or Me+ to the electron-rich ketenyl O of (S2CNMe2)(dppe)(OC)W(C,C-η2-OC:CCH2Ph) yields cationic W(II) alkyne complexes of the type [(S2CNMe2)(dppe)(OC)W(η2-ROC≡CCH2Ph)][BF4] (R = H, Me). The conversion from a d6 alkyne complex to a d4 alkoxyalkyne complex presented here combines electrophilic addn. at ligand β-positions, effectively oxidizing the metal, with known carbyne-carbonyl coupling reactions. The (S2CNEt2)(dppe)(OC)W(C,C-η2-OC=CCH2Ph) (I) complex was characterized by x-ray crystallog.
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(c) Mayr, A.; Bastos, C. M.; Chang, R. T.; Haberman, J. X.; Robinson, K. S.; Belle-Oudry, D. A. Assistance by Electrophiles in Photoinduced Alkylidyne–Carbonyl Coupling. Angew. Chem., Int. Ed. Engl. 1992, 31, 747– 749, DOI: 10.1002/anie.199207471
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6
Sivavec, T. M.; Katz, T. J. Synthesis of phenols from metal-carbynes and diynes. Tetrahedron Lett. 1985, 26, 2159– 2162, DOI: 10.1016/S0040-4039(00)98950-0
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6
Synthesis of phenols from metal-carbynes and diynes
Sivavec, Timothy M.; Katz, Thomas J.
Tetrahedron Letters (1985), 26 (18), 2159-62CODEN: TELEAY; ISSN:0040-4039.
Metal carbynes RC≡M(CO)4Br (R = Me, Ph; M = W, Cr) were treated with diynes R1C≡C(CH2)nC≡CH (R1 = H, Me, Ph; n = 2-4) or (MeO2C)2C(CH2C≡CH)2 followed by acid hydrolysis to yield phenols I or II, resp.
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7
Select reviews on [2 + 2 + 2] cycloaddition:
(a) Lautens, M.; Klute, W.; Tam, W. Transition Metal-Mediated Cycloaddition Reactions. Chem. Rev. 1996, 96, 49– 92, DOI: 10.1021/cr950016l
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7a
Transition Metal-Mediated Cycloaddition Reactions
Lautens, Mark; Klute, Wolfgang; Tam, William
Chemical Reviews (Washington, D. C.) (1996), 96 (1), 49-92CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
A review with 226 refs. A discussion of established and interesting new cycloaddn. reactions promoted by metal species is presented.
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(b) Inglesby, P. A.; Evans, P. A. Stereoselective transition metal-catalysed higher-order carbocyclisation reactions. Chem. Soc. Rev. 2010, 39, 2791– 805, DOI: 10.1039/b913110h
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7b
Stereoselective transition metal-catalysed higher-order carbocyclisation reactions
Inglesby, Phillip A.; Evans, P. Andrew
Chemical Society Reviews (2010), 39 (8), 2791-2805CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
A review. Transition metal-catalyzed higher-order carbocyclization reactions represent an important class of reactions due to their ability to construct complex polycyclic systems in a highly selective and atom-economical fashion. A key and striking feature with these transformations is the dichotomy in reactivity that a substrate displays with different transition metal complexes, which is akin to the manner enzymes direct terpene biosynthesis. This tutorial review details the historical development of higher-order carbocyclization reactions, specifically the variants of [m+2+2] that involve carbon-based π-systems, where m = 2, 3 and 4, in the context of crit. developments with various transition metal complexes.
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(c) Tanaka, K.; Shibata, Y. Rhodium-Catalyzed [2 + 2+2] Cycloaddition of Alkynes for the Synthesis of Substituted Benzenes: Catalysts, Reaction Scope, and Synthetic Applications. Synthesis 2012, 44, 323– 350, DOI: 10.1055/s-0031-1289665
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7c
Rhodium-catalyzed [2+2+2] cycloaddition of alkynes for the synthesis of substituted benzenes: catalysts, reaction scope, and synthetic applications
Shibata, Yu; Tanaka, Ken
Synthesis (2012), 44 (3), 323-350CODEN: SYNTBF; ISSN:0039-7881. (Georg Thieme Verlag)
A review. The transition-metal-catalyzed [2+2+2] cycloaddn. of alkynes is a useful and atom-economical method for the synthesis of substituted benzenes. This comprehensive review covered the [2+2+2] cycloaddn. reactions catalyzed by rhodium complexes. Applications of the rhodium-catalyzed [2+2+2] cycloaddn. in the synthesis of functional org. compds. were also described.
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(d) Thakur, A.; Louie, J. Advances in nickel-catalyzed cycloaddition reactions to construct carbocycles and heterocycles. Acc. Chem. Res. 2015, 48, 2354– 65, DOI: 10.1021/acs.accounts.5b00054
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7d
Advances in Nickel-Catalyzed Cycloaddition Reactions To Construct Carbocycles and Heterocycles
Thakur, Ashish; Louie, Janis
Accounts of Chemical Research (2015), 48 (8), 2354-2365CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)
A review. Transition-metal catalysis has revolutionized the field of org. synthesis by facilitating the construction of complex org. mols. in a highly efficient manner. Although these catalysts are typically based on precious metals, researchers have made great strides in discovering new base metal catalysts over the past decade. This account describes the authors' efforts in this area and details the development of versatile Ni complexes that catalyze a variety of cycloaddn. reactions to afford interesting carbocycles and heterocycles. First, the authors describe their early work in investigating the efficacy of N-heterocyclic carbene (NHC) ligands in Ni-catalyzed cycloaddn. reactions with carbon dioxide and isocyanate. The use of sterically hindered, electron donating NHC ligands in these reactions significantly improved the substrate scope as well as reaction conditions in the syntheses of a variety of pyrones and pyridones. The high reactivity and versatility of these unique Ni(NHC) catalytic systems allowed the authors to develop unprecedented Ni-catalyzed cycloaddns. that were unexplored due to the inefficacy of early Ni catalysts to promote hetero-oxidative coupling steps. The authors describe the development and mechanistic anal. of Ni/NHC catalysts that couple diynes and nitriles to form pyridines. Kinetic studies and stoichiometric reactions confirmed a hetero-oxidative coupling pathway assocd. with this Ni-catalyzed cycloaddn. The authors, next, describe a series of new substrates for Ni-catalyzed cycloaddn. reactions such as vinylcyclopropanes, aldehydes, ketones, tropones, 3-azetidinones, and 3-oxetanones. In reactions with vinycyclopropanes and tropones, DFT calcns. reveal noteworthy mechanistic steps such as a C-C σ-bond activation and an 8π-insertion of vinylcyclopropane and tropone, resp. Similarly, the cycloaddn. of 3-azetidinones and 3-oxetanones also requires Ni-catalyzed C-C σ-bond activation to form N- and O-contg. heterocycles.
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8
(a) Protasiewicz, J. D.; Lippard, S. J. Vanadium-Promoted Reductive Coupling of CO and Facile Hydrogenation to Form cis-Disiloxyethylenes. J. Am. Chem. Soc. 1991, 113, 6564– 6570, DOI: 10.1021/ja00017a030
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8a
Vanadium-promoted reductive coupling of carbon monoxide and facile hydrogenation to form cis-disiloxyethylenes
Protasiewicz, John D.; Lippard, Stephen J.
Journal of the American Chemical Society (1991), 113 (17), 6564-70CODEN: JACSAT; ISSN:0002-7863.
Reaction of trimethylsilyl reagents with Na[V(CO)2(dmpe)2] (I; dmpe = Me2PCH2CH2PMe2) leads to reductive coupling of the 2 CO ligands to form a coordinated bis(trimethylsiloxy)acetylene ligand. Me3SiOTf (OTf = triflate) gave a novel 6-coordinate, paramagnetic (μeff = 2.81 μB at 20 K) complex [V(Me3SiOC≡COSiMe3)(dmpe)2]OTf, while addn. of Me3SiBr afforded diamagnetic [V(Me3SiOC≡COSiMe3)(dmpe)2Br], analogs of which are known in Nb and Ta chem. Both complexes were characterized in the solid state by single-crystal x-ray diffraction, and the latter was identified in soln. by NMR spectroscopy. Significantly, these V complexes react with H at room temp. and mild pressures in the absence of external catalysts to afford exclusively cis-Me3SiOCH:CHOSiMe3 in good yield. In an expt. designed to study the mechanism of this reductive coupling, V carbyne species were prepd. by adding 1 equiv of a trialkyl- or triarylsilyl chloride to I. One such complex, [V(COSiPh3)(CO)(dmpe)2], was crystd. and characterized structurally as the 1st unambiguous example of a V carbyne complex. Carbynes of this kind are known intermediates in the reductive coupling of CO ligands in [M(CO)2(dmpe)2X] compds. (M = Nb, Ta; X = halide, triflate). These results extend significantly the generality of CO reductive coupling chem. to a 1st-row transition metal.
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(b) Bianconi, P. A.; Williams, I. D.; Engeler, M. P.; Lippard, S. J. Reductive Coupling of Two Carbon Monoxide Ligands to Form a Coordinated Alkyne. J. Am. Chem. Soc. 1986, 108, 311– 313, DOI: 10.1021/ja00262a030
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8b
Reductive coupling of two carbon monoxide ligands to form a coordinated alkyne
Bianconi, Patricia A.; Williams, Ian D.; Engeler, Mary P.; Lippard, Stephen J.
Journal of the American Chemical Society (1986), 108 (2), 311-13CODEN: JACSAT; ISSN:0002-7863.
Two CO mols. bound to Ta in [Ta(CO)2(dmpe)2Cl] [I, dmpe = 1,2-bis(dimethylphosphino)ethane] are reductively coupled to form a new C-C bond. The resulting bis(trimethylsiloxy)ethyne is bonded to the Ta atom in the product [Ta(Me3SiOC≡COSiMe3)(dmpe)2X], [X = Cl (II), SiMe3 (III)]. The reaction is effected by addn. of Mg dust, activated by I2 or HgCl2, to a THF soln. of I in the presence of a Lewis acid, (C5R5)2MCl2 (M = Ti, R = H, Me; M = Zr, R = Me). An intermediate isocarbonyl species (IV) formed in this reaction is identified by IR. Addn. of Me3SiCl to solns. of IV leads, upon workup, to a crystn. mixt. of II and III. Conditions for prepg. pure II are described, whereas III has only been identified by its 1H, 13C, 31P NMR and IR spectral properties. The structure of II was detd. in an x-ray crystal structure anal. The Ta atom sits on a twofold axis passing through the Ta-Cl bond and the midpoint of the alkyne C≡C bond.
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(c) Bronk, B. S.; Protasiewicz, J. D.; Lippard, S. J. Reductive Coupling of Group 5 Dicarbonyls to Disiloxyacetylene Complexes: Ring Formation and Effects of Increasing Steric Demands. Organometallics 1995, 14, 1385– 1392, DOI: 10.1021/om00003a044
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8c
Reductive Coupling of Group 5 Dicarbonyls to Disiloxyacetylene Complexes: Ring Formation and Effects of Increasing Steric Demands
Bronk, Brian S.; Protasiewicz, John D.; Lippard, Stephen J.
Organometallics (1995), 14 (3), 1385-92CODEN: ORGND7; ISSN:0276-7333. (American Chemical Society)
Convenient syntheses of dicarbonyl complexes [M(CO)2(depe)2Cl] (depe = 1,2-bis(diethylphosphino)ethane, M = Ta (1), Nb (3)) and [M(CO)2(dbpe)2Cl] (dbpe = 1,2-bis(dibutylphosphino)ethane, M = Ta (2), Nb (4)) having increased steric demands at the high coordinate metal centers are described. Single crystal x-ray structural studies were carried out for two reductively coupled products prepd. with 1,2-bis(chlorodimethylsilyl)ethane as the electrophile, I (M = V, R = Me) (monoclinic, space group C2/c, a 9.349(2), b 20.548(3), c 16.146(4) Å, β 104.79(1)°) and I (M = Ta, R = Et) (monoclinic, space group Cc, a 11.512(1), b 18.311(3), c 18.493(3) Å, β 97.322(7)°). In these complexes, the acetylene is contained within a newly formed eight-membered ring, and the ligands are arranged in a pentagonal bipyramid geometry comprising two axial P atoms and five equatorial ligands, the coupled carbons, a trans chloride, and the remaining two P atoms.
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9
(a) Reppe, W.; v. Kutepow, N.; Magin, A. Cyclization of Acetylenic Compounds. Angew. Chem., Int. Ed. Engl. 1969, 8, 727– 733, DOI: 10.1002/anie.196907271
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9a
Cyclization of acetylenic compounds
Reppe, W.; Von Kutepow, N.; Magin, A.
Angewandte Chemie, International Edition in English (1969), 8 (10), 727-33CODEN: ACIEAY; ISSN:0570-0833.
A review, with 21 references, of the cyclization of alkynes to benzenes, the prepn. of hydroquinone from acetylene and Fe(CO)5, the reaction of alkylated alkynes with CO and water to give alkylated hydroquinones, and the prepn. of unsatd. dilactones.
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(b) Pino, P.; Braca, G.; Sbrana, G.; Cuccuru, A. Chem. Ind. 1968, 1732
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9b
Carbonylation of acetylene with [Ru(CO)4]3 as catalyst
Pino, Piero; Braca, Giuseppe; Sbrana, Giuseppe; Cuccuru, A.
Chemistry & Industry (London, United Kingdom) (1968), (49), 1732-3CODEN: CHINAG; ISSN:0009-3068.
Hydroquinone (I) is prepd. from acetylene, CO, and H at 200-20° in the presence of [Ru(CO)4]3 (II) in tetrahydrofuran (THF), and from C2H2, CO, and water in the presence of II at 190-250° in THF, Me2CO, PhMe, and MeCN. Thus, 0.248 mole C2H2 is treated with CO (partial pressure 120 atm.) and H (partial pressure 10 atm.) 268 min. at 200° in 177 g. THF in the presence of 0.1 g. II to give 58.5% I; 34.6% I is obtained when the H partial pressure is 75 atm. Acetylene (0.109 mole) ls treated with CO (initial partial pressure 53 atm.) and water in 65.0 g. THF in the presence of 0.1 g. II at 190° to give 58.0% I.
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(c) Suzuki, N.; Kondo, T.; Mitsudo, T.-A. Novel Ruthenium-Catalyzed Cross-Carbonylation of Alkynes and 2-Norbornenes to Hydroquinones. Organometallics 1998, 17, 766– 769, DOI: 10.1021/om970880z
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9c
Novel Ruthenium-Catalyzed Cross-Carbonylation of Alkynes and 2-Norbornenes to Hydroquinones
Suzuki, Nobuyoshi; Kondo, Teruyuki; Mitsudo, Take-aki
Organometallics (1998), 17 (4), 766-769CODEN: ORGND7; ISSN:0276-7333. (American Chemical Society)
Unsym. substituted hydroquinones were obtained in high yields by the novel ruthenium-catalyzed cross-carbonylation of alkynes and 2-norbornenes. For example, treatment of 4-octyne and 2-norbornene with 2 mol % Ru3(CO)12 in N-methylpiperidine under 60 atm of carbon monoxide at 140° for 20 h gave 4,5-dipropyltricyclo[6.2.1.02,7]undeca-2(7),3,5-triene-3,6-diol (I) in 85% yield. The reaction apparently involves a maleoylruthenium intermediate, which is generated by the reaction of an alkyne and two mols. of carbon monoxide on ruthenium.
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10
(a) Fürstner, A. Alkyne Metathesis on the Rise. Angew. Chem., Int. Ed. 2013, 52, 2794– 2819, DOI: 10.1002/anie.201204513
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10a
Alkyne Metathesis on the Rise
Fuerstner, Alois
Angewandte Chemie, International Edition (2013), 52 (10), 2794-2819CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
A review. The early years of alkyne metathesis were marked by a somewhat ironic state of affairs: the proposed mechanism was swiftly validated and more than one effective catalyst became available shortly after the discovery of this transformation; surprisingly, however, the impact on synthesis remained very limited for a long period of time. Recent advances, however, suggest that this situation is about to change: the remarkable activity, functional-group tolerance, and reliability of the latest generation of catalysts open the door for highly advanced applications. The resulting (cyclo)alkynes are amenable to numerous postmetathetic transformations, which diversify the product portfolio and bring many different structural motifs into reach. Since the catalysts have also evolved from the glovebox to the benchtop, there should be little barrier left for a wider use of this reaction in org. synthesis.
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(b) Engel, P. F.; Pfeffer, M. Carbon-Carbon and Carbon-Heteroatom Coupling Reactions of Metallacarbynes. Chem. Rev. 1995, 95, 2281– 2309, DOI: 10.1021/cr00039a002
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10b
Carbon-Carbon and Carbon-Heteroatom Coupling Reactions of Metallacarbynes
Engel, Philippus F.; Pfeffer, Michel
Chemical Reviews (Washington, D. C.) (1995), 95 (7), 2281-309CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
A review with > 220 refs.
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(c) Wang, Z.; Herraiz, A. G.; del Hoyo, A. M.; Suero, M. G. Generating carbyne equivalents with photoredox catalysis. Nature 2018, 554, 86– 91, DOI: 10.1038/nature25185
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10c
Generating carbyne equivalents with photoredox catalysis
Wang, Zhaofeng; Herraiz, Ana G.; del Hoyo, Ana M.; Suero, Marcos G.
Nature (London, United Kingdom) (2018), 554 (7690), 86-91CODEN: NATUAS; ISSN:0028-0836. (Nature Research)
Carbon has the unique ability to bind four atoms and form stable tetravalent structures that are prevalent in nature. The lack of one or two valences leads to a set of species-carbocations, carbanions, radicals and carbenes-that is fundamental to our understanding of chem. reactivity. In contrast, the carbyne-a monovalent carbon with three non-bonded electrons-is a relatively unexplored reactive intermediate; the design of reactions involving a carbyne is limited by challenges assocd. with controlling its extreme reactivity and the lack of efficient sources. Given the innate ability of carbynes to form three new covalent bonds sequentially, we anticipated that a catalytic method of generating carbynes or related stabilized species would allow what we term an 'assembly point' disconnection approach for the construction of chiral centers. Here we describe a catalytic strategy that generates diazomethyl radicals as direct equiv. of carbyne species using visible-light photoredox catalysis. The ability of these carbyne equiv. to induce site-selective carbon-hydrogen bond cleavage in arom. rings enables a useful diazomethylation reaction, which underpins sequencing control for the late-stage assembly-point functionalization of medically relevant agents. Our strategy provides an efficient route to libraries of potentially bioactive mols. through the installation of tailored chiral centers at carbon-hydrogen bonds, while complementing current translational late-stage functionalization processes. Furthermore, we exploit the dual radical and carbene character of the generated carbyne equiv. in the direct transformation of abundant chem. feedstocks into valuable chiral mols.
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(d) Wang, Z.; Jiang, L.; Sarró, P.; Suero, M. G. Catalytic Cleavage of C(sp²)–C(sp²) Bonds with Rh-Carbynoids. J. Am. Chem. Soc. 2019, 141, 15509– 15514, DOI: 10.1021/jacs.9b08632
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10d
Catalytic Cleavage of C(sp2)-C(sp2) Bonds with Rh-Carbynoids
Wang, Zhaofeng; Jiang, Liyin; Sarro, Pau; Suero, Marcos G.
Journal of the American Chemical Society (2019), 141 (39), 15509-15514CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
We report a catalytic strategy that generates rhodium-carbynoids by selective diazo activation of designed carbyne sources. We found that rhodium-carbynoid species provoke C(sp2)-C(sp2) bond scission in alkenes by inserting a monovalent carbon unit between both sp2-hybridized carbons. This skeletal remodeling process accesses synthetically useful allyl cation intermediates that conduct to valuable allylic building blocks upon nucleophile attack. Our results rely on the formation of cyclopropyl-I(III) intermediates able to undergo electrocyclic ring-opening, following the Woodward-Hoffmann-DePuy rules.
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11
(a) Sato, H.; Bender, M.; Chen, W. J.; Krische, M. J. Diols, α-Ketols, and Diones as 22π Components in [2 + 2+2] Cycloadditions of 1,6-Diynes via Ruthenium(0)-Catalyzed Transfer Hydrogenation. J. Am. Chem. Soc. 2016, 138, 16244– 16247, DOI: 10.1021/jacs.6b11746
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11a
Diols, α-Ketols, and Diones as 22π Components in [2+2+2] Cycloadditions of 1,6-Diynes via Ruthenium(0)-Catalyzed Transfer Hydrogenation
Sato, Hiroki; Bender, Matthias; Chen, Weijie; Krische, Michael J.
Journal of the American Chemical Society (2016), 138 (50), 16244-16247CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
The first use of vicinal diols, ketols, or diones as 22π components in metal-catalyzed [2+2+2] cycloaddn. is described. Using ruthenium(0) catalysts, 1,6-diynes form ruthenacyclopentadienes that engage transient diones in successive carbonyl addn. Transfer hydrogenolysis of the resulting ruthenium(II) diolate mediated by the diol or ketol reactant releases the cycloadduct with regeneration of ruthenium(0) and the requisite dione.
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(b) Shibata, T.; Yamashita, K.; Ishida, H.; Takagi, K. Iridium Complex Catalyzed Carbonylative Alkyne–Alkyne Coupling for the Synthesis of Cyclopentadienones. Org. Lett. 2001, 3, 1217– 1219, DOI: 10.1021/ol015708c
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11b
Iridium Complex Catalyzed Carbonylative Alkyne-Alkyne Coupling for the Synthesis of Cyclopentadienones
Shibata, Takanori; Yamashita, Koji; Ishida, Hiroyuki; Takagi, Kentaro
Organic Letters (2001), 3 (8), 1217-1219CODEN: ORLEF7; ISSN:1523-7060. (American Chemical Society)
Fused cyclopentadienones I [X = O, H2C, (EtO2C)2C, (PhCH2O2C)2C; R = Ph3Si, Ph, 4-MeOC6H4, 4-ClC6H4, 4-MeO2CC6H4] are prepd. in 52-99% yields by catalytic carbonylative alkyne-alkyne coupling of the bisalkynes RC≡CCH2XCH2C≡CR II using iridium diphosphine complexes under carbon monoxide at atm. pressure or a partial pressure of 0.2 atm. Either Ir(1,5-COD)(Ph2PCH2CH2CH2PPh2)Cl2 or Ir(1,5-COD)(Ph3P)2Cl2 (Vaska's complex) are optimal catalysts for this process. E.g., stirring II [R = Ph; X = (PhCH2O2C)2C] in xylene under 1 atm. CO pressure at 120° in the presence of Vaska's complex for 2-7 h gives I [R = Ph; X = (PhCH2O2C)2C] in 99% yield. The crystal structure of the chloroform solvate of the iridium biphosphine Ir(1,5-COD)(Ph2PCH2CH2CH2PPh2)Cl2 [Ir(COD)(dppp)Cl2·CHCl3] was detd.
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(c) Lee, S. I.; Son, S. U.; Choi, M. R.; Chung, Y. K.; Lee, S.-G. Co/C-catalyzed tandem carbocyclization reaction of 1,6-diynes. Tetrahedron Lett. 2003, 44, 4705– 4709, DOI: 10.1016/S0040-4039(03)01053-0
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11c
Co/C-catalyzed tandem carbocyclization reaction of 1,6-diynes
Lee, Sang Ick; Son, Seung Uk; Choi, Mi Ra; Chung, Young Keun; Lee, Sueg-Geun
Tetrahedron Letters (2003), 44 (25), 4705-4709CODEN: TELEAY; ISSN:0040-4039. (Elsevier Science Ltd.)
Cobalt on charcoal (Co/C) can be used as a catalyst in the tandem carbocycloaddn. reaction of 1,6-diynes and carbon monoxide. The reaction products, e.g., I and II, depend on the reaction temp., the position of functional groups, and the substrate itself.
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12
(a) Yamamoto, Y.; Miyabe, Y.; Itoh, K. Synthesis of a Dinuclear Ruthenabicyclic Complex and Its Ligand-Substitution Reactions. Eur. J. Inorg. Chem. 2004, 3651– 3661, DOI: 10.1002/ejic.200400128
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12a
Synthesis of a dinuclear ruthenabicyclic complex and its ligand-substitution reactions
Yamamoto, Yoshihiko; Miyabe, Yumiko; Itoh, Kenji
European Journal of Inorganic Chemistry (2004), (18), 3651-3661CODEN: EJICFO; ISSN:1434-1948. (Wiley-VCH Verlag GmbH & Co. KGaA)
Binuclear η5-dihydrofurano-ruthenacyclopentadiene ruthenium half-sandwich complexes I were prepd. by coupling of bis-propargyl ether O(CH2C≡CCO2Me)2 with Ru3(CO)12. Reaction of Ru3(CO)12 with O(CH2C≡CCO2Me)2 gave I, L1, L2, L3, L4 = CO (3a), ligand substitution with Me3NO gave trimethylamine complex (12, shown as I, L1 = Me3N, L2, L3, L4 = CO). Phosphines react with 12 giving products of mono- and di-substitution, [13a-c, shown as I, L2, L3, L4 = CO, L1 = PPh3, monodentate Ph2PCH2CH2PPh2 and Ph2P(2-Py); 14, L3-L4 = dppm-P,P', L1, L2 = CO; 15b,c; L1-L2 = dppe-P,P', Ph2P(2-Py)-P,N, L3, L3 = CO]. When a phenyl-substituted diyne O(CH2C≡CPh)2 was employed, a cyclopentadienone complex was formed together with the expected dinuclear ruthenacycle complex. In contrast, O(CH2C≡CTMS)2 gave the corresponding cyclopentadienone complex as the only product. The dinuclear mono(amine)ruthenacycle complex also reacted with di-Me butynedioate (DMAD) in refluxing THF to afford a novel μ-η2-alkyne complex [16, shown as I, L3-L4 = C(CO2Me):C(CO2Me)] together with the [2+2+2] cycloadduct between the diyne and DMAD. The highly electron-deficient character of DMAD is imperative for the formation of the μ-alkyne complex. Me propiolate and diphenylacetylene gave no corresponding μ-alkyne complexes.
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(b) Kim, M.-S.; Lee, J. W.; Lee, J. E.; Kang, J. Synthesis of Enantiopure Ruthenium Tricarbonyl Complexes of a Bicyclic Cyclopentadienone Derivative. Eur. J. Inorg. Chem. 2008, 2008, 2510– 2513, DOI: 10.1002/ejic.200800174
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(c) Sato, H.; Bender, M.; Chen, W.; Krische, M. J. Diols, α-Ketols, and Diones as 2_2π Components in [2 + 2+2] Cycloadditions of 1,6-Diynes via Ruthenium(0)-Catalyzed Transfer Hydrogenation. J. Am. Chem. Soc. 2016, 138, 16244– 16247, DOI: 10.1021/jacs.6b11746
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12c
Diols, α-Ketols, and Diones as 22π Components in [2+2+2] Cycloadditions of 1,6-Diynes via Ruthenium(0)-Catalyzed Transfer Hydrogenation
Sato, Hiroki; Bender, Matthias; Chen, Weijie; Krische, Michael J.
Journal of the American Chemical Society (2016), 138 (50), 16244-16247CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
The first use of vicinal diols, ketols, or diones as 22π components in metal-catalyzed [2+2+2] cycloaddn. is described. Using ruthenium(0) catalysts, 1,6-diynes form ruthenacyclopentadienes that engage transient diones in successive carbonyl addn. Transfer hydrogenolysis of the resulting ruthenium(II) diolate mediated by the diol or ketol reactant releases the cycloadduct with regeneration of ruthenium(0) and the requisite dione.
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(d) Yamamoto, Y.; Yamashita, K.; Nakamura, M. Synthesis of Organometallic Analogues of Spirocyclic C-Arylribosides. Organometallics 2010, 29, 1472– 1478, DOI: 10.1021/om100043f
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12d
Synthesis of Organometallic Analogues of Spirocyclic C-Arylribosides
Yamamoto, Yoshihiko; Yamashita, Ken; Nakamura, Mitsutaka
Organometallics (2010), 29 (6), 1472-1478CODEN: ORGND7; ISSN:0276-7333. (American Chemical Society)
Spirocyclic C-riboside/ruthenium cyclopentadienone complex hybrid mols. were synthesized from silyldiynes, which were derived from the protected γ-ribonolactone and Ru3(CO)12. The structure and stereochem. of the obtained complexes were unambiguously confirmed by x-ray crystallog. The catalytic activity of selected complexes was tested in the hydrogenation of acetophenone and ruthenium hydride species were obsd. by 1H NMR spectroscopy.
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13
(a) Casey, C. P.; Andrews, M. A.; Rinz, J. E. Rhenium formyl and carboxy complexes derived from the cyclopentadienyl(dicarbonyl)nitrosylrhenium(1+) cation: models for the Fischer–Tropsch and water gas shift reactions. J. Am. Chem. Soc. 1979, 101, 741– 743, DOI: 10.1021/ja00497a045
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13a
Rhenium formyl and carboxy complexes derived from the cyclopentadienyl(dicarbonyl)nitrosylrhenium(1+) cation: models for the Fischer-Tropsch and water gas shift reactions
Casey, Charles P.; Andrews, Mark A.; Rinz, James E.
Journal of the American Chemical Society (1979), 101 (3), 741-3CODEN: JACSAT; ISSN:0002-7863.
The reaction of (C5H5)Re(CO)2(NO)+PF6- with K+ HB[OCHMe2]3- in THF gives (C5H5)Re(CO)(NO)(CHO) (I), a neutral transition metal formyl complex. Dil. solns. of I gradually decomp. to give (C5H5)Re(CO)(NO)(H). Redn. of I with BH3.THF yields (C5H5)Re(CO)(NO)(Me) while redn. of I with Li+ HBEt3- gives (C5H5)Re(NO)(CHO)2-, the first bis formyl metal complex. Reaction of (C5H5)Re(CO)2(NO)+PF6- with NaOH in water-ether gives the carboxy complex (C5H5)Re(CO)(NO)(CO2H) which reacts with CF3CO2H to reform the starting cation. Treatment of the carboxy complex with Et3N converts it to the hydride (C5H5)Re(CO)(NO)(H). The reaction of (C5H5)Re(CO)2(NO)+PF6- with NaBH4 in benzene-water yields formyl complex I as the major product, not (C5H5)Re(CO)(NO)(CH2OH) as previously reported.
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(b) Nicholas, K. M. Possible intermediacy of hydrocarbyne complexes in carbon monoxide reduction. Organometallics 1982, 1, 1713– 1715, DOI: 10.1021/om00072a031
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13b
Possible intermediacy of hydrocarbyne complexes in carbon monoxide reduction
Nicholas, K. M.
Organometallics (1982), 1 (12), 1713-15CODEN: ORGND7; ISSN:0276-7333.
Thermochem. data, modified EHMO calcns., and reactivity and kinetic data suggest that hydroxycarbyne complexes may be important intermediates in homogeneous transition-metal-catalyzed CO redn.
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(c) Fu, X.; Wayland, B. B. Thermodynamics of Rhodium Hydride Reactions with CO, Aldehydes, and Olefins in Water: Organo-Rhodium Porphyrin Bond Dissociation Free Energies. J. Am. Chem. Soc. 2005, 127, 16460– 16467, DOI: 10.1021/ja054548n
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13c
Thermodynamics of Rhodium Hydride Reactions with CO, Aldehydes, and Olefins in Water: Organo-Rhodium Porphyrin Bond Dissociation Free Energies
Fu, Xuefeng; Wayland, Bradford B.
Journal of the American Chemical Society (2005), 127 (47), 16460-16467CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
Tetra(p-sulfonato-phenyl) porphyrin Rh hydride ([(TSPP)Rh-D(D2O)]-4) (1) reacts in H2O (D2O) with CO, aldehydes, and olefins to produce metallo formyl, α-hydroxyalkyl, and alkyl complexes, resp. The hydride complex (1) functions as a weak acid in D2O and partially dissocs. into a Rh(I) complex ([(TSPP)RhI(D2O)]-5) and a proton (D+). Fast substrate reactions of 1 in D2O compared to reactions of Rh porphyrin hydride ((por)Rh-H) in benzene are ascribed to aq. media promoting formation of ions and supporting ionic reaction pathways. The regioselectivity for addn. of 1 to olefins is predominantly anti-Markovnikov in acidic D2O and exclusively anti-Markovnikov in basic D2O. The range of accessible equil. thermodn. measurements for Rh hydride substrate reactions is substantially increased in H2O compared to that in org. media through exploiting the H ion dependence for the equil. distribution of species in aq. media. Thermodn. measurements are reported for reactions of a Rh porphyrin hydride in H2O with each of the substrates, including CO, H2CO, CH3CHO, CH2:CH2, and sets of aldehydes and olefins. Reactions of Rh porphyrin hydrides with CO and aldehydes have nearly equal free-energy changes in H2O and benzene, but alkene reactions that form hydrophobic alkyl groups are substantially less favorable in H2O than in benzene. Bond dissocn. free energies in H2O are derived from thermodn. results for (TSPP)Rh-organo complexes in aq. soln. for Rh-CDO, Rh-CH(R)OD, and Rh-CH2CH(D)R units and are compared with related values detd. in benzene.
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(d) Imler, G. H.; Zdilla, M. J.; Wayland, B. B. Equilibrium Thermodynamics To Form a Rhodium Formyl Complex from Reactions of CO and H₂: Metal σ Donor Activation of CO. J. Am. Chem. Soc. 2014, 136, 5856– 5859, DOI: 10.1021/ja501173d
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13d
Equilibrium Thermodynamics To Form a Rhodium Formyl Complex from Reactions of CO and H2: Metal σ Donor Activation of CO
Imler, Gregory H.; Zdilla, Michael J.; Wayland, Bradford B.
Journal of the American Chemical Society (2014), 136 (16), 5856-5859CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
A Rh(II) dibenzotetramethylaza[14]annulene dimer ([(tmtaa)Rh]2) (1) reacts with CO and H2 in toluene and pyridine to form equil. distributions with hydride and formyl complexes ((tmtaa)Rh-H (2); (tmtaa)Rh-C(O)H (3)). The Rh formyl complex ((tmtaa)Rh-C(O)H) was isolated under a CO/H2 atmosphere, and the mol. structure was detd. by x-ray diffraction. Equil. consts. were evaluated for reactions of (tmtaa)Rh-H with CO to produce formyl complexes in toluene (K2(298 K)(tol) = 10.8 (1.0) × 103) and pyridine (K2(298 K)(py) = 2.2 (0.2) × 103). Reactions of 1 and 2 in toluene and pyridine are discussed in the context of alternative radical and ionic pathways. The five-coordinate 18-electron Rh(I) complex ([(py)(tmtaa)Rh(I)]-) is proposed to function as a nucleophile toward CO to give a two-electron activated bent Rh-CO unit. Results from DFT calcns. on the (tmtaa)Rh system correlate well with exptl. observations. Reactions of 1 with CO and H2 suggest metal catalyst design features to reduce the activation barriers for homogeneous CO hydrogenation.
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(e) Teets, T. S.; Labinger, J. A.; Bercaw, J. E. Guanidine-Functionalized Rhenium Cyclopentadienyl Carbonyl Complexes: Synthesis and Cooperative Activation of H–H and O–H Bonds. Organometallics 2014, 33, 4107– 4117, DOI: 10.1021/om500650b
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13e
Guanidine-functionalized rhenium cyclopentadienyl carbonyl complexes: synthesis and cooperative activation of H-H and O-H bonds
Teets, Thomas S.; Labinger, Jay A.; Bercaw, John E.
Organometallics (2014), 33 (15), 4107-4117CODEN: ORGND7; ISSN:0276-7333. (American Chemical Society)
Catalytic reactions utilizing carbon monoxide as a substrate are numerous, and they typically involve selective functionalization of a metal-bound CO. We have developed Group 7 carbonyl complexes where secondary coordination sphere, Lewis acidic functionalities can assist in the activation of substrate mols., mainly in the context of syngas conversion. This work describes a new class of cyclopentadienyl (Cp) rhenium carbonyl compds. of the type [Re(η5-C5H4DMEG)(CO)3-n(NO)n]n (DMEG = dimethylethyleneguanidine or 1,3-dimethylimidazolidin-2-imino, n = 0, 1), where a tethered guanidine base is appended to the Cp ring to participate in cooperative substrate activation with the electrophilic carbonyl. A reliable synthetic route for these complexes is presented, with crystallog. characterization of the free-base and protonated forms for both the carbonyl and mixed carbonyl-nitrosyl complexes. The latter are employed as platforms to study heterolytic H-H and O-H bond cleavage reactions that result in nucleophilic CO functionalization. The corresponding formyl complex is prepd. by hydride transfer, and by measuring its hydricity (ΔG°H-) and pKa of the protonated base, the free energy of H2 cleavage is found to be +3.3(6) kcal/mol. The activation of methanol to form methoxycarbonyl complexes is found to be more favorable, with ΔG° ≈ 0 for the intramol. addn. of methanol to the guanidine-appended carbonyl complex. A detailed thermodn. study is described for both the intramol. methanol activation reaction and related intermol. reactions with external bases. The results highlight some tangible thermodn. benefits of tethering the base in the secondary coordination sphere.
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(f) Wiedner, E. S.; Appel, A. M. Thermochemical Insight into the Reduction of CO to CH₃OH with [Re(CO)]⁺ and [Mn(CO)]⁺ Complexes. J. Am. Chem. Soc. 2014, 136, 8661– 8668, DOI: 10.1021/ja502316e
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13f
Thermochemical Insight into the Reduction of CO to CH3OH with [Re(CO)]+ and [Mn(CO)]+ Complexes
Wiedner, Eric S.; Appel, Aaron M.
Journal of the American Chemical Society (2014), 136 (24), 8661-8668CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
To gain insight into thermodn. barriers for redn. of CO into CH3OH, free energies for redn. of [CpRe(PPh3)(NO)(CO)]+ into CpRe(PPh3)(NO)(CH2OH) have been detd. from exptl. measurements. Using model complexes, the free energies for the transfer of H+, H-, and e- have been detd. A pKa of 10.6 was estd. for [CpRe(PPh3)(NO)(CHOH)]+ by measuring the pKa for the analogous [CpRe(PPh3)(NO)(CMeOH)]+. The hydride donor ability (ΔG°H-) of CpRe(PPh3)(NO)(CH2OH) was estd. to be 58.0 kcal mol-1, based on calorimetry measurements of the hydride-transfer reaction between CpRe(PPh3)(NO)(CHO) and [CpRe(PPh3)(NO)(CHOMe)]+ to generate the methylated analog, CpRe(PPh3)(NO)(CH2OMe). Cyclic voltammograms recorded on CpRe(PPh3)(NO)(CMeO), CpRe(PPh3)(NO)(CH2OMe), and [CpRe(PPh3)(NO)(CHOMe)]+ displayed either a quasireversible oxidn. (neutral species) or redn. (cationic species). These potentials were used as ests. for the oxidn. of CpRe(PPh3)(NO)(CHO) or CpRe(PPh3)(NO)(CH2OH) or the redn. of [CpRe(PPh3)(NO)(CHOH)]+. Combination of the thermodn. data permits construction of three-dimensional free energy landscapes under varying conditions of pH and PH2. The free energy for H2 addn. (ΔG°H2) to [CpRe(PPh3)(NO)(CO)]+ (+15 kcal mol-1) was identified as the most significant thermodn. impediment for the redn. of CO. DFT computations on a series of [CpXM(L)(NO)(CO)]+ (M = Re, Mn) complexes indicate that ΔG°H2 can be varied by 11 kcal mol-1 through variation of both the ancillary ligands and the metal.
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Churchill, M. R.; Wasserman, H. J.; Holmes, S. J.; Schrock, R. R. Coupling of methylidyne and carbonyl ligands on tungsten. Crystal structure of W(η²-HC≡COAlCl₃)(CO)(PMe₃)₃Cl. Organometallics 1982, 1, 766– 768, DOI: 10.1021/om00065a022
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14
Coupling of methylidyne and carbonyl ligands on tungsten. Crystal structure of W(η2-HC≡COAlCl3)(CO)(PMe3)3Cl
Churchill, Melvyn Rowen; Wasserman, Harvey J.; Holmes, S. J.; Schrock, R. R.
Organometallics (1982), 1 (5), 766-8CODEN: ORGND7; ISSN:0276-7333.
(Me3P)4W(CH)Cl reacts with CO in the presence of AlX3 (X = Me, Cl) to give complexes (Me3P)3W(η2-HC≡COAlX3)(CO)Cl (I). Single crystals of I (X = Cl) are monoclinic, space group P21/c. The essentially planar HC≡COAl system is best regarded as a coordinated acetylene deriv. The role of AlX3 is postulated to be 2-fold, i.e., removal of 1 of the Me3P ligands and activation of either the methylidyne or CO ligand toward the coupling reaction.
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Chatani, N.; Shinohara, M.; Ikeda, S.; Murai, S. Reductive Oligomerization of Carbon Monoxide by Rhodium-Catalyzed Reaction with Hydrosilanes. J. Am. Chem. Soc. 1997, 119, 4303– 4304, DOI: 10.1021/ja9631561
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15
Reductive Oligomerization of Carbon Monoxide by Rhodium-Catalyzed Reaction with Hydrosilanes
Chatani, Naoto; Shinohara, Masaaki; Ikeda, Shin-ichi; Murai, Shinji
Journal of the American Chemical Society (1997), 119 (18), 4303-4304CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
The reaction of CO with HSiEt2Me at 140° in the presence of [RhCl2(CO)2]2/Et3N in C6H6 gave MeEt2SiOSiEt2Me as the main product (31% yield) along with reductive coupling of CO which gave diethylmethylsiloxymethane (I), 1,2-bis(diethylmethylsiloxy)ethylene (II), and 1,2,3-tris(diethylmethoxylsiloxy)propylene (III). The reaction of CO with with HSiMe2Ph gave 1,2-bis(dimethylphenylsiloxy)ethylene in yields as high as 62%. The key intermediates were a carbyne-metal complex and dioxyacetylene-metal complex. The reaction of paraformaldehyde with HSiEt2Me and CO in the presence of [RhCl(CO)2]2/Et3N for 1 day gave MeEt2SiOSiEt2Me, I (1%), II (10%), and III (5%), in yields comparable to those obsd. for reactions without paraformaldehyde.
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Abstract
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Scheme 1
Scheme 1. Water–Gas Shift Reaction for the Synthesis of Catechols from 1,6-Diynes
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Scheme 2
Scheme 2. Reaction of Diphenyl Diyne
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Figure 1
Figure 1. Single-crystal X-ray structure of compound 3m (Ru, green; C, gray; O, red). Thermal elipsoids are shown at 50% probability. Selected bond lengths (Å) and angles [degs]: avg Ru–C_(C≡O) = 1.936(2); avg C–O_(C≡O) = 1.130(2); avg C_(C≡O)–Ru–C_(C≡O) = 94.86(7).
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Scheme 3
Scheme 3. Reaction of Alkyne Bearing a Terminal Nitrile
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Scheme 4
Scheme 4. Proposed Reaction Pathway
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Scheme 5
Scheme 5. Formation of Ene–Diol in the Absence of Diene
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References
This article references 15 other publications.
1. 1
  (a) Ambrosi, A.; Denmark, S. E. Harnessing the Power of the Water-Gas Shift Reaction for Organic Synthesis. Angew. Chem., Int. Ed. 2016, 55, 12164– 89, DOI: 10.1002/anie.201601803
  1a
  Harnessing the Power of the Water-Gas Shift Reaction for Organic Synthesis
  Ambrosi, Andrea; Denmark, Scott E.
  Angewandte Chemie, International Edition (2016), 55 (40), 12164-12189CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
  A review. Since its original discovery over a century ago, the water-gas shift reaction (WGSR) has played a crucial role in industrial chem., providing a source of H2 to feed fundamental industrial transformations such as the Haber-Bosch synthesis of ammonia. Although the prodn. of hydrogen remains nowadays the major application of the WGSR, the advent of homogeneous catalysis in the 1970s marked the beginning of a synergy between WGSR and org. chem. Thus, the reducing power provided by the CO/H2O couple has been exploited in the synthesis of fine chems.; not only hydrogenation-type reactions, but also catalytic processes that require a reductive step for the turnover of the catalytic cycle. Despite the potential and unique features of the WGSR, its applications in org. synthesis remain largely underdeveloped. The topic will be critically reviewed herein, with the expectation that an increased awareness may stimulate new, creative work in the area.
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  (b) Schaper, L.-A.; Herrmann, W. A.; Kühn, F. E. Water-Gas Shift Reaction. Applied Homogeneous Catalysis with Organometallic Compounds 2017, 1689– 1698, DOI: 10.1002/9783527651733.ch38
  There is no corresponding record for this reference.
2. 2
  For selected recent reports using the WGS reaction for transformations of organic molecules, see:
  (a) Beucher, H.; Merino, E.; Genoux, A.; Fox, T.; Nevado, C. κ³-(N^C^C)Gold(III) Carboxylates: Evidence for Decarbonylation Processes. Angew. Chem., Int. Ed. 2019, 58, 9064– 9067, DOI: 10.1002/anie.201903098
  2a
  κ3-(N̂ĈC)Gold(III) Carboxylates: Evidence for Decarbonylation Processes
  Beucher, Helene; Merino, Estibaliz; Genoux, Alexandre; Fox, Thomas; Nevado, Cristina
  Angewandte Chemie, International Edition (2019), 58 (27), 9064-9067CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
  Gold(III) carboxylate species, stabilized by a κ3-(N̂ĈC) ligand template, are presented herein. A η1-AuIII-C(O)-OH species has been characterized under cryogenic conditions as a result of the nucleophilic attack of an ammonium hydroxide onto a dinuclear μ-CO2-κ3-(N̂ĈC)AuIII precursor. Thermal decompn. for these species proceeds by an unusual decarbonylation process, in contrast to typical decarboxylation pathways obsd. in related metallocarboxylic acids.
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  (b) Kolesnikov, P. N.; Usanov, D. L.; Muratov, K. M.; Chusov, D. Dichotomy of Atom-Economical Hydrogen-Free Reductive Amidation vs Exhaustive Reductive Amination. Org. Lett. 2017, 19, 5657– 5660, DOI: 10.1021/acs.orglett.7b02821
  2b
  Dichotomy of Atom-Economical Hydrogen-Free Reductive Amidation vs Exhaustive Reductive Amination
  Kolesnikov, Pavel N.; Usanov, Dmitry L.; Muratov, Karim M.; Chusov, Denis
  Organic Letters (2017), 19 (20), 5657-5660CODEN: ORLEF7; ISSN:1523-7052. (American Chemical Society)
  Rh-catalyzed one-step reductive amidation of aldehydes was developed. The protocol does not require an external hydrogen source and employs carbon monoxide as a deoxygenative agent. The direction of the reaction can be altered simply by changing the solvent: reaction in THF leads to amides, whereas methanol favors formation of tertiary amines.
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  (c) Zhou, P.; Yu, C.; Jiang, L.; Lv, K.; Zhang, Z. One-pot reductive amination of carbonyl compounds with nitro compounds with CO/H₂O as the hydrogen donor over non-noble cobalt catalyst. J. Catal. 2017, 352, 264– 273, DOI: 10.1016/j.jcat.2017.05.026
  2c
  One-pot reductive amination of carbonyl compounds with nitro compounds using CO/H2O as the hydrogen donor over non-noble cobalt catalyst
  Zhou, Peng; Yu, Changlin; Jiang, Liang; Lv, Kangle; Zhang, Zehui
  Journal of Catalysis (2017), 352 (), 264-273CODEN: JCTLA5; ISSN:0021-9517. (Elsevier Inc.)
  The one-pot reductive amination of nitro compds. RNO2 [R = (CH2)2CH3, c-C6H11, C6H5, etc.] with carbonyl compds. R1C(O)R2 [R1 = CH(CH3)2, C6H5, c-C6H11, 4-pyridyl, etc.; R2 = H; R1R2 = -(CH2)5-] over heterogeneous non-noble metal catalysts was developed for the first time by transfer hydrogenation with CO/H2O as the hydrogen donor. Nitrogen-doped carbon supported cobalt nanoparticles were obsd. to be active toward this reaction, affording structurally-diverse secondary amines RNHCHR1R2 with high yields. Kinetic studies revealed that the transfer hydrogenation of imines (C=N bonds) was the rate-detg. step. Reaction mechanism studies indicated that both nitrogen and cobalt nanoparticles were important for the transfer hydrogenation with CO/H2O to generate the proton (N-H+) and hydride (Co-H-) as the active species. Furthermore, the heterogeneous cobalt catalyst was highly stable without the loss of its catalytic activity during the recycling expts.
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  (d) Ibrahim, M. Y. S.; Denmark, S. E. Palladium/Rhodium Cooperative Catalysis for the Production of Aryl Aldehydes and Their Deuterated Analogues Using the Water-Gas Shift Reaction. Angew. Chem., Int. Ed. 2018, 57, 10362– 10367, DOI: 10.1002/anie.201806148
  2d
  Palladium/Rhodium Cooperative Catalysis for the Production of Aryl Aldehydes and Their Deuterated Analogues Using the Water-Gas Shift Reaction
  Ibrahim, Malek Y. S.; Denmark, Scott E.
  Angewandte Chemie, International Edition (2018), 57 (32), 10362-10367CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
  A novel Pd/Rh dual-metallic cooperative catalytic process has been developed to effect the reductive carbonylation of aryl halides in moderate to good yield. In this reaction, water is the hydride source, and CO serves both as the carbonyl source and the terminal reductant through the water-gas shift reaction. The catalytic generation of the Rh hydride allows for the selective formation of highly hindered aryl aldehydes that are inaccessible through previously reported reductive carbonylation protocols. Moreover, aldehydes with deuterated formyl groups can be efficiently and selectively synthesized using D2O as a cost-effective deuterium source without the need for presynthesizing the aldehyde.
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3. 3
  Chatani, N.; Fukumoto, Y.; Ida, T.; Murai, S. Ruthenium-catalyzed reaction of 1,6-diynes with hydrosilanes and carbon monoxide: a third way of incorporating CO. J. Am. Chem. Soc. 1993, 115, 11614– 11615, DOI: 10.1021/ja00077a077
  3
  Ruthenium-catalyzed reaction of 1,6-diynes with hydrosilanes and carbon monoxide: a third way of incorporating CO
  Chatani, Naoto; Fukumoto, Yoshiya; Ida, Tomohide; Murai, Shinji
  Journal of the American Chemical Society (1993), 115 (24), 11614-15CODEN: JACSAT; ISSN:0002-7863.
  A new ruthenium-catalyzed carbonylation of 1,6-diynes with HSiR3 (R = alkyl) and carbon monoxide leading to catechol derivs. was reported. For example, carbonylation of di-Et bis(2-propynyl)malonate I (1,6-diyne) gave 5-(tert-butyldimethylsiloxy)-1,3-dihydro-6-hydroxy-2H-indenedicarboxylate II and 5,6-bis(tert-butyldimethylsiloxy)-1,3-dihydro-2H-indenedicarboxylate III. The formation of an intermediate siloxy-carbyne complex or hydroxy-carbyne complex was proposed; an oxycarbyne-based catalyst cycle was discussed.
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4. 4
  (a) Ingle, W. M.; Preti, G.; MacDiarmid, A. G. Cobalt to oxygen migration of the trimethylsilyl group in trimethylsilylcobalt tetracarbonyl. J. Chem. Soc., Chem. Commun. 1973, 497– 498, DOI: 10.1039/c39730000497
  4a
  Cobalt to oxygen migration of the trimethylsilyl group in (trimethylsilyl)cobalt tetracarbonyl
  Ingle, William M.; Preti, George; MacDiarmid, Alan G.
  Journal of the Chemical Society, Chemical Communications (1973), (14), 497-8CODEN: JCCCAT; ISSN:0022-4936.
  Heating Me3SiCo(CO)4 at 105° for 50 hr in a sealed tube gave Me3SiOCCo3(CO)9 (I) and (Me3SiOC)4Co2(CO)4 (II) by migration of the Me3Si group from Co to O. II contains bridging Me3SiOC≡COSiMe3 groups, and had no bridging CO groups and no Co-Co double bond character as in (tert-BuC≡CBu-tert)2Fe2(CO)4. Reaction of Me3SiCo(CO)4 with THF for 1 hr at room temp. gave I.
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  (b) Fuchs, J.; Irran, E.; Hrobarik, P.; Klare, H. F. T.; Oestreich, M. Si-H Bond Activation with Bullock’s Cationic Tungsten(II) Catalyst: CO as Cooperating Ligand. J. Am. Chem. Soc. 2019, 141, 18845– 18850, DOI: 10.1021/jacs.9b10304
  4b
  Si-H Bond Activation with Bullock's Cationic Tungsten(II) Catalyst: CO as Cooperating Ligand
  Fuchs, Julien; Irran, Elisabeth; Hrobarik, Peter; Klare, Hendrik F. T.; Oestreich, Martin
  Journal of the American Chemical Society (2019), 141 (47), 18845-18850CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
  An in-depth investigation of the reaction of tertiary hydrosilanes with [CpW(CO)2(IMes)]+[B(C6F5)4]- reveals a fundamentally new Si-H bond activation mode. Unlike the originally proposed oxidative addn. of the Si-H bond to the tungsten(II) center, there is strong exptl. and NMR spectroscopic evidence for the involvement of one of the CO ligands of the cationic complex in the Si-H bond breaking event. The Si-H bond is heterolytically cleaved to form a tungsten(II) hydride and a silylium ion, which is stabilized by one of the CO ligands. This reactive hydrosilane adduct was eventually isolated and characterized by X-ray diffraction anal. Quantum-chem. calcns. support a cooperative mechanism, but a stepwise process consisting of oxidative addn. and subsequent tungsten-to-oxygen silyl migration in the tungsten(IV) silyl hydride is also energetically feasible. However, our combined spectroscopic and computational anal. favors the cooperative pathway. The newly identified hydrosilane adduct is the key intermediate of Bullock's ionic carbonyl hydrosilylation.
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5. 5
  (a) Fischer, E. O.; Friedrich, P. Complex-Stabilized Hydroxy (p-tolyl)acetylene by Reaction of trans-Chlorotetracarbonyl(tolylcarbyne)tungsten with Acetylacetone. Angew. Chem., Int. Ed. Engl. 1979, 18, 327– 328, DOI: 10.1002/anie.197903271
  There is no corresponding record for this reference.
  (b) Birdwhistell, K. R.; Tonker, T. L.; Templeton, J. L.; Kenan, W. R. Transformation of a tungsten(0) alkyne to a tungsten(II) alkyne via vinylidene, carbyne, and ketenyl ligands. J. Am. Chem. Soc. 1985, 107, 4474– 4483, DOI: 10.1021/ja00301a017
  5b
  Transformation of a tungsten(0) alkyne to a tungsten(II) alkyne via vinylidene, carbyne, and ketenyl ligands
  Birdwhistell, K. R.; Tonker, T. L.; Templeton, J. L.; Kenan, W. R., Jr.
  Journal of the American Chemical Society (1985), 107 (15), 4474-83CODEN: JACSAT; ISSN:0002-7863.
  Rearrangement of the W(0) d6 η2-alkyne complex fac-(dppe)(OC)3W(η2-PhC≡CH) (dppe = Ph2PCH2CH2PPh2) yields a meridional tricarbonyltungsten vinylidene complex, mer-(dppe)(OC)3W:C:CHPh, which provides an M-C-C framework for further ligand-based transformations. Electrophilic addn. at the β-C atom of the vinylidene ligand generates a cationic W carbyne, [mer-(dppe)(CO)3W≡CCH2Ph][BF4]. This carbyne cation undergoes CO substitution by Cl-, Br- and iodide, and in the absence of added ligand thermal dissocn. of CO it allows isolation of the highly electrophilic [(dppe)(OC)2W≡CCH2Ph][BF4] complex. This reagent adds F- to form a trans-FW≡CCH2Ph unit in (dppe)(OC)2FW≡CCH2Ph and also adds neutral ligands to form cationic dicarbonyl derivs., [(dppe)(OC)2LW≡CCH2Ph][BF4] (L = PMe3, MeCOMe, H2O). Addn. of dithiocarbamate salts -S2CNR2 (R = Me, Et) to the electrophilic dicarbonyl cation initially forms an η1-S2CNR2 adduct, which leads to coupling of carbyne and CO ligands to form an η2-ketenyl complex upon chelation of the dithiocarbamate ligand. Addn. of H+ or Me+ to the electron-rich ketenyl O of (S2CNMe2)(dppe)(OC)W(C,C-η2-OC:CCH2Ph) yields cationic W(II) alkyne complexes of the type [(S2CNMe2)(dppe)(OC)W(η2-ROC≡CCH2Ph)][BF4] (R = H, Me). The conversion from a d6 alkyne complex to a d4 alkoxyalkyne complex presented here combines electrophilic addn. at ligand β-positions, effectively oxidizing the metal, with known carbyne-carbonyl coupling reactions. The (S2CNEt2)(dppe)(OC)W(C,C-η2-OC=CCH2Ph) (I) complex was characterized by x-ray crystallog.
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  (c) Mayr, A.; Bastos, C. M.; Chang, R. T.; Haberman, J. X.; Robinson, K. S.; Belle-Oudry, D. A. Assistance by Electrophiles in Photoinduced Alkylidyne–Carbonyl Coupling. Angew. Chem., Int. Ed. Engl. 1992, 31, 747– 749, DOI: 10.1002/anie.199207471
  There is no corresponding record for this reference.
6. 6
  Sivavec, T. M.; Katz, T. J. Synthesis of phenols from metal-carbynes and diynes. Tetrahedron Lett. 1985, 26, 2159– 2162, DOI: 10.1016/S0040-4039(00)98950-0
  6
  Synthesis of phenols from metal-carbynes and diynes
  Sivavec, Timothy M.; Katz, Thomas J.
  Tetrahedron Letters (1985), 26 (18), 2159-62CODEN: TELEAY; ISSN:0040-4039.
  Metal carbynes RC≡M(CO)4Br (R = Me, Ph; M = W, Cr) were treated with diynes R1C≡C(CH2)nC≡CH (R1 = H, Me, Ph; n = 2-4) or (MeO2C)2C(CH2C≡CH)2 followed by acid hydrolysis to yield phenols I or II, resp.
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7. 7
  Select reviews on [2 + 2 + 2] cycloaddition:
  (a) Lautens, M.; Klute, W.; Tam, W. Transition Metal-Mediated Cycloaddition Reactions. Chem. Rev. 1996, 96, 49– 92, DOI: 10.1021/cr950016l
  7a
  Transition Metal-Mediated Cycloaddition Reactions
  Lautens, Mark; Klute, Wolfgang; Tam, William
  Chemical Reviews (Washington, D. C.) (1996), 96 (1), 49-92CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
  A review with 226 refs. A discussion of established and interesting new cycloaddn. reactions promoted by metal species is presented.
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  (b) Inglesby, P. A.; Evans, P. A. Stereoselective transition metal-catalysed higher-order carbocyclisation reactions. Chem. Soc. Rev. 2010, 39, 2791– 805, DOI: 10.1039/b913110h
  7b
  Stereoselective transition metal-catalysed higher-order carbocyclisation reactions
  Inglesby, Phillip A.; Evans, P. Andrew
  Chemical Society Reviews (2010), 39 (8), 2791-2805CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)
  A review. Transition metal-catalyzed higher-order carbocyclization reactions represent an important class of reactions due to their ability to construct complex polycyclic systems in a highly selective and atom-economical fashion. A key and striking feature with these transformations is the dichotomy in reactivity that a substrate displays with different transition metal complexes, which is akin to the manner enzymes direct terpene biosynthesis. This tutorial review details the historical development of higher-order carbocyclization reactions, specifically the variants of [m+2+2] that involve carbon-based π-systems, where m = 2, 3 and 4, in the context of crit. developments with various transition metal complexes.
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  (c) Tanaka, K.; Shibata, Y. Rhodium-Catalyzed [2 + 2+2] Cycloaddition of Alkynes for the Synthesis of Substituted Benzenes: Catalysts, Reaction Scope, and Synthetic Applications. Synthesis 2012, 44, 323– 350, DOI: 10.1055/s-0031-1289665
  7c
  Rhodium-catalyzed [2+2+2] cycloaddition of alkynes for the synthesis of substituted benzenes: catalysts, reaction scope, and synthetic applications
  Shibata, Yu; Tanaka, Ken
  Synthesis (2012), 44 (3), 323-350CODEN: SYNTBF; ISSN:0039-7881. (Georg Thieme Verlag)
  A review. The transition-metal-catalyzed [2+2+2] cycloaddn. of alkynes is a useful and atom-economical method for the synthesis of substituted benzenes. This comprehensive review covered the [2+2+2] cycloaddn. reactions catalyzed by rhodium complexes. Applications of the rhodium-catalyzed [2+2+2] cycloaddn. in the synthesis of functional org. compds. were also described.
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  (d) Thakur, A.; Louie, J. Advances in nickel-catalyzed cycloaddition reactions to construct carbocycles and heterocycles. Acc. Chem. Res. 2015, 48, 2354– 65, DOI: 10.1021/acs.accounts.5b00054
  7d
  Advances in Nickel-Catalyzed Cycloaddition Reactions To Construct Carbocycles and Heterocycles
  Thakur, Ashish; Louie, Janis
  Accounts of Chemical Research (2015), 48 (8), 2354-2365CODEN: ACHRE4; ISSN:0001-4842. (American Chemical Society)
  A review. Transition-metal catalysis has revolutionized the field of org. synthesis by facilitating the construction of complex org. mols. in a highly efficient manner. Although these catalysts are typically based on precious metals, researchers have made great strides in discovering new base metal catalysts over the past decade. This account describes the authors' efforts in this area and details the development of versatile Ni complexes that catalyze a variety of cycloaddn. reactions to afford interesting carbocycles and heterocycles. First, the authors describe their early work in investigating the efficacy of N-heterocyclic carbene (NHC) ligands in Ni-catalyzed cycloaddn. reactions with carbon dioxide and isocyanate. The use of sterically hindered, electron donating NHC ligands in these reactions significantly improved the substrate scope as well as reaction conditions in the syntheses of a variety of pyrones and pyridones. The high reactivity and versatility of these unique Ni(NHC) catalytic systems allowed the authors to develop unprecedented Ni-catalyzed cycloaddns. that were unexplored due to the inefficacy of early Ni catalysts to promote hetero-oxidative coupling steps. The authors describe the development and mechanistic anal. of Ni/NHC catalysts that couple diynes and nitriles to form pyridines. Kinetic studies and stoichiometric reactions confirmed a hetero-oxidative coupling pathway assocd. with this Ni-catalyzed cycloaddn. The authors, next, describe a series of new substrates for Ni-catalyzed cycloaddn. reactions such as vinylcyclopropanes, aldehydes, ketones, tropones, 3-azetidinones, and 3-oxetanones. In reactions with vinycyclopropanes and tropones, DFT calcns. reveal noteworthy mechanistic steps such as a C-C σ-bond activation and an 8π-insertion of vinylcyclopropane and tropone, resp. Similarly, the cycloaddn. of 3-azetidinones and 3-oxetanones also requires Ni-catalyzed C-C σ-bond activation to form N- and O-contg. heterocycles.
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8. 8
  (a) Protasiewicz, J. D.; Lippard, S. J. Vanadium-Promoted Reductive Coupling of CO and Facile Hydrogenation to Form cis-Disiloxyethylenes. J. Am. Chem. Soc. 1991, 113, 6564– 6570, DOI: 10.1021/ja00017a030
  8a
  Vanadium-promoted reductive coupling of carbon monoxide and facile hydrogenation to form cis-disiloxyethylenes
  Protasiewicz, John D.; Lippard, Stephen J.
  Journal of the American Chemical Society (1991), 113 (17), 6564-70CODEN: JACSAT; ISSN:0002-7863.
  Reaction of trimethylsilyl reagents with Na[V(CO)2(dmpe)2] (I; dmpe = Me2PCH2CH2PMe2) leads to reductive coupling of the 2 CO ligands to form a coordinated bis(trimethylsiloxy)acetylene ligand. Me3SiOTf (OTf = triflate) gave a novel 6-coordinate, paramagnetic (μeff = 2.81 μB at 20 K) complex [V(Me3SiOC≡COSiMe3)(dmpe)2]OTf, while addn. of Me3SiBr afforded diamagnetic [V(Me3SiOC≡COSiMe3)(dmpe)2Br], analogs of which are known in Nb and Ta chem. Both complexes were characterized in the solid state by single-crystal x-ray diffraction, and the latter was identified in soln. by NMR spectroscopy. Significantly, these V complexes react with H at room temp. and mild pressures in the absence of external catalysts to afford exclusively cis-Me3SiOCH:CHOSiMe3 in good yield. In an expt. designed to study the mechanism of this reductive coupling, V carbyne species were prepd. by adding 1 equiv of a trialkyl- or triarylsilyl chloride to I. One such complex, [V(COSiPh3)(CO)(dmpe)2], was crystd. and characterized structurally as the 1st unambiguous example of a V carbyne complex. Carbynes of this kind are known intermediates in the reductive coupling of CO ligands in [M(CO)2(dmpe)2X] compds. (M = Nb, Ta; X = halide, triflate). These results extend significantly the generality of CO reductive coupling chem. to a 1st-row transition metal.
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  (b) Bianconi, P. A.; Williams, I. D.; Engeler, M. P.; Lippard, S. J. Reductive Coupling of Two Carbon Monoxide Ligands to Form a Coordinated Alkyne. J. Am. Chem. Soc. 1986, 108, 311– 313, DOI: 10.1021/ja00262a030
  8b
  Reductive coupling of two carbon monoxide ligands to form a coordinated alkyne
  Bianconi, Patricia A.; Williams, Ian D.; Engeler, Mary P.; Lippard, Stephen J.
  Journal of the American Chemical Society (1986), 108 (2), 311-13CODEN: JACSAT; ISSN:0002-7863.
  Two CO mols. bound to Ta in [Ta(CO)2(dmpe)2Cl] [I, dmpe = 1,2-bis(dimethylphosphino)ethane] are reductively coupled to form a new C-C bond. The resulting bis(trimethylsiloxy)ethyne is bonded to the Ta atom in the product [Ta(Me3SiOC≡COSiMe3)(dmpe)2X], [X = Cl (II), SiMe3 (III)]. The reaction is effected by addn. of Mg dust, activated by I2 or HgCl2, to a THF soln. of I in the presence of a Lewis acid, (C5R5)2MCl2 (M = Ti, R = H, Me; M = Zr, R = Me). An intermediate isocarbonyl species (IV) formed in this reaction is identified by IR. Addn. of Me3SiCl to solns. of IV leads, upon workup, to a crystn. mixt. of II and III. Conditions for prepg. pure II are described, whereas III has only been identified by its 1H, 13C, 31P NMR and IR spectral properties. The structure of II was detd. in an x-ray crystal structure anal. The Ta atom sits on a twofold axis passing through the Ta-Cl bond and the midpoint of the alkyne C≡C bond.
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  (c) Bronk, B. S.; Protasiewicz, J. D.; Lippard, S. J. Reductive Coupling of Group 5 Dicarbonyls to Disiloxyacetylene Complexes: Ring Formation and Effects of Increasing Steric Demands. Organometallics 1995, 14, 1385– 1392, DOI: 10.1021/om00003a044
  8c
  Reductive Coupling of Group 5 Dicarbonyls to Disiloxyacetylene Complexes: Ring Formation and Effects of Increasing Steric Demands
  Bronk, Brian S.; Protasiewicz, John D.; Lippard, Stephen J.
  Organometallics (1995), 14 (3), 1385-92CODEN: ORGND7; ISSN:0276-7333. (American Chemical Society)
  Convenient syntheses of dicarbonyl complexes [M(CO)2(depe)2Cl] (depe = 1,2-bis(diethylphosphino)ethane, M = Ta (1), Nb (3)) and [M(CO)2(dbpe)2Cl] (dbpe = 1,2-bis(dibutylphosphino)ethane, M = Ta (2), Nb (4)) having increased steric demands at the high coordinate metal centers are described. Single crystal x-ray structural studies were carried out for two reductively coupled products prepd. with 1,2-bis(chlorodimethylsilyl)ethane as the electrophile, I (M = V, R = Me) (monoclinic, space group C2/c, a 9.349(2), b 20.548(3), c 16.146(4) Å, β 104.79(1)°) and I (M = Ta, R = Et) (monoclinic, space group Cc, a 11.512(1), b 18.311(3), c 18.493(3) Å, β 97.322(7)°). In these complexes, the acetylene is contained within a newly formed eight-membered ring, and the ligands are arranged in a pentagonal bipyramid geometry comprising two axial P atoms and five equatorial ligands, the coupled carbons, a trans chloride, and the remaining two P atoms.
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9. 9
  (a) Reppe, W.; v. Kutepow, N.; Magin, A. Cyclization of Acetylenic Compounds. Angew. Chem., Int. Ed. Engl. 1969, 8, 727– 733, DOI: 10.1002/anie.196907271
  9a
  Cyclization of acetylenic compounds
  Reppe, W.; Von Kutepow, N.; Magin, A.
  Angewandte Chemie, International Edition in English (1969), 8 (10), 727-33CODEN: ACIEAY; ISSN:0570-0833.
  A review, with 21 references, of the cyclization of alkynes to benzenes, the prepn. of hydroquinone from acetylene and Fe(CO)5, the reaction of alkylated alkynes with CO and water to give alkylated hydroquinones, and the prepn. of unsatd. dilactones.
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  (b) Pino, P.; Braca, G.; Sbrana, G.; Cuccuru, A. Chem. Ind. 1968, 1732
  9b
  Carbonylation of acetylene with [Ru(CO)4]3 as catalyst
  Pino, Piero; Braca, Giuseppe; Sbrana, Giuseppe; Cuccuru, A.
  Chemistry & Industry (London, United Kingdom) (1968), (49), 1732-3CODEN: CHINAG; ISSN:0009-3068.
  Hydroquinone (I) is prepd. from acetylene, CO, and H at 200-20° in the presence of [Ru(CO)4]3 (II) in tetrahydrofuran (THF), and from C2H2, CO, and water in the presence of II at 190-250° in THF, Me2CO, PhMe, and MeCN. Thus, 0.248 mole C2H2 is treated with CO (partial pressure 120 atm.) and H (partial pressure 10 atm.) 268 min. at 200° in 177 g. THF in the presence of 0.1 g. II to give 58.5% I; 34.6% I is obtained when the H partial pressure is 75 atm. Acetylene (0.109 mole) ls treated with CO (initial partial pressure 53 atm.) and water in 65.0 g. THF in the presence of 0.1 g. II at 190° to give 58.0% I.
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  (c) Suzuki, N.; Kondo, T.; Mitsudo, T.-A. Novel Ruthenium-Catalyzed Cross-Carbonylation of Alkynes and 2-Norbornenes to Hydroquinones. Organometallics 1998, 17, 766– 769, DOI: 10.1021/om970880z
  9c
  Novel Ruthenium-Catalyzed Cross-Carbonylation of Alkynes and 2-Norbornenes to Hydroquinones
  Suzuki, Nobuyoshi; Kondo, Teruyuki; Mitsudo, Take-aki
  Organometallics (1998), 17 (4), 766-769CODEN: ORGND7; ISSN:0276-7333. (American Chemical Society)
  Unsym. substituted hydroquinones were obtained in high yields by the novel ruthenium-catalyzed cross-carbonylation of alkynes and 2-norbornenes. For example, treatment of 4-octyne and 2-norbornene with 2 mol % Ru3(CO)12 in N-methylpiperidine under 60 atm of carbon monoxide at 140° for 20 h gave 4,5-dipropyltricyclo[6.2.1.02,7]undeca-2(7),3,5-triene-3,6-diol (I) in 85% yield. The reaction apparently involves a maleoylruthenium intermediate, which is generated by the reaction of an alkyne and two mols. of carbon monoxide on ruthenium.
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10. 10
  (a) Fürstner, A. Alkyne Metathesis on the Rise. Angew. Chem., Int. Ed. 2013, 52, 2794– 2819, DOI: 10.1002/anie.201204513
  10a
  Alkyne Metathesis on the Rise
  Fuerstner, Alois
  Angewandte Chemie, International Edition (2013), 52 (10), 2794-2819CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
  A review. The early years of alkyne metathesis were marked by a somewhat ironic state of affairs: the proposed mechanism was swiftly validated and more than one effective catalyst became available shortly after the discovery of this transformation; surprisingly, however, the impact on synthesis remained very limited for a long period of time. Recent advances, however, suggest that this situation is about to change: the remarkable activity, functional-group tolerance, and reliability of the latest generation of catalysts open the door for highly advanced applications. The resulting (cyclo)alkynes are amenable to numerous postmetathetic transformations, which diversify the product portfolio and bring many different structural motifs into reach. Since the catalysts have also evolved from the glovebox to the benchtop, there should be little barrier left for a wider use of this reaction in org. synthesis.
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  (b) Engel, P. F.; Pfeffer, M. Carbon-Carbon and Carbon-Heteroatom Coupling Reactions of Metallacarbynes. Chem. Rev. 1995, 95, 2281– 2309, DOI: 10.1021/cr00039a002
  10b
  Carbon-Carbon and Carbon-Heteroatom Coupling Reactions of Metallacarbynes
  Engel, Philippus F.; Pfeffer, Michel
  Chemical Reviews (Washington, D. C.) (1995), 95 (7), 2281-309CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
  A review with > 220 refs.
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  (c) Wang, Z.; Herraiz, A. G.; del Hoyo, A. M.; Suero, M. G. Generating carbyne equivalents with photoredox catalysis. Nature 2018, 554, 86– 91, DOI: 10.1038/nature25185
  10c
  Generating carbyne equivalents with photoredox catalysis
  Wang, Zhaofeng; Herraiz, Ana G.; del Hoyo, Ana M.; Suero, Marcos G.
  Nature (London, United Kingdom) (2018), 554 (7690), 86-91CODEN: NATUAS; ISSN:0028-0836. (Nature Research)
  Carbon has the unique ability to bind four atoms and form stable tetravalent structures that are prevalent in nature. The lack of one or two valences leads to a set of species-carbocations, carbanions, radicals and carbenes-that is fundamental to our understanding of chem. reactivity. In contrast, the carbyne-a monovalent carbon with three non-bonded electrons-is a relatively unexplored reactive intermediate; the design of reactions involving a carbyne is limited by challenges assocd. with controlling its extreme reactivity and the lack of efficient sources. Given the innate ability of carbynes to form three new covalent bonds sequentially, we anticipated that a catalytic method of generating carbynes or related stabilized species would allow what we term an 'assembly point' disconnection approach for the construction of chiral centers. Here we describe a catalytic strategy that generates diazomethyl radicals as direct equiv. of carbyne species using visible-light photoredox catalysis. The ability of these carbyne equiv. to induce site-selective carbon-hydrogen bond cleavage in arom. rings enables a useful diazomethylation reaction, which underpins sequencing control for the late-stage assembly-point functionalization of medically relevant agents. Our strategy provides an efficient route to libraries of potentially bioactive mols. through the installation of tailored chiral centers at carbon-hydrogen bonds, while complementing current translational late-stage functionalization processes. Furthermore, we exploit the dual radical and carbene character of the generated carbyne equiv. in the direct transformation of abundant chem. feedstocks into valuable chiral mols.
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  (d) Wang, Z.; Jiang, L.; Sarró, P.; Suero, M. G. Catalytic Cleavage of C(sp²)–C(sp²) Bonds with Rh-Carbynoids. J. Am. Chem. Soc. 2019, 141, 15509– 15514, DOI: 10.1021/jacs.9b08632
  10d
  Catalytic Cleavage of C(sp2)-C(sp2) Bonds with Rh-Carbynoids
  Wang, Zhaofeng; Jiang, Liyin; Sarro, Pau; Suero, Marcos G.
  Journal of the American Chemical Society (2019), 141 (39), 15509-15514CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
  We report a catalytic strategy that generates rhodium-carbynoids by selective diazo activation of designed carbyne sources. We found that rhodium-carbynoid species provoke C(sp2)-C(sp2) bond scission in alkenes by inserting a monovalent carbon unit between both sp2-hybridized carbons. This skeletal remodeling process accesses synthetically useful allyl cation intermediates that conduct to valuable allylic building blocks upon nucleophile attack. Our results rely on the formation of cyclopropyl-I(III) intermediates able to undergo electrocyclic ring-opening, following the Woodward-Hoffmann-DePuy rules.
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11. 11
  (a) Sato, H.; Bender, M.; Chen, W. J.; Krische, M. J. Diols, α-Ketols, and Diones as 22π Components in [2 + 2+2] Cycloadditions of 1,6-Diynes via Ruthenium(0)-Catalyzed Transfer Hydrogenation. J. Am. Chem. Soc. 2016, 138, 16244– 16247, DOI: 10.1021/jacs.6b11746
  11a
  Diols, α-Ketols, and Diones as 22π Components in [2+2+2] Cycloadditions of 1,6-Diynes via Ruthenium(0)-Catalyzed Transfer Hydrogenation
  Sato, Hiroki; Bender, Matthias; Chen, Weijie; Krische, Michael J.
  Journal of the American Chemical Society (2016), 138 (50), 16244-16247CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
  The first use of vicinal diols, ketols, or diones as 22π components in metal-catalyzed [2+2+2] cycloaddn. is described. Using ruthenium(0) catalysts, 1,6-diynes form ruthenacyclopentadienes that engage transient diones in successive carbonyl addn. Transfer hydrogenolysis of the resulting ruthenium(II) diolate mediated by the diol or ketol reactant releases the cycloadduct with regeneration of ruthenium(0) and the requisite dione.
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  (b) Shibata, T.; Yamashita, K.; Ishida, H.; Takagi, K. Iridium Complex Catalyzed Carbonylative Alkyne–Alkyne Coupling for the Synthesis of Cyclopentadienones. Org. Lett. 2001, 3, 1217– 1219, DOI: 10.1021/ol015708c
  11b
  Iridium Complex Catalyzed Carbonylative Alkyne-Alkyne Coupling for the Synthesis of Cyclopentadienones
  Shibata, Takanori; Yamashita, Koji; Ishida, Hiroyuki; Takagi, Kentaro
  Organic Letters (2001), 3 (8), 1217-1219CODEN: ORLEF7; ISSN:1523-7060. (American Chemical Society)
  Fused cyclopentadienones I [X = O, H2C, (EtO2C)2C, (PhCH2O2C)2C; R = Ph3Si, Ph, 4-MeOC6H4, 4-ClC6H4, 4-MeO2CC6H4] are prepd. in 52-99% yields by catalytic carbonylative alkyne-alkyne coupling of the bisalkynes RC≡CCH2XCH2C≡CR II using iridium diphosphine complexes under carbon monoxide at atm. pressure or a partial pressure of 0.2 atm. Either Ir(1,5-COD)(Ph2PCH2CH2CH2PPh2)Cl2 or Ir(1,5-COD)(Ph3P)2Cl2 (Vaska's complex) are optimal catalysts for this process. E.g., stirring II [R = Ph; X = (PhCH2O2C)2C] in xylene under 1 atm. CO pressure at 120° in the presence of Vaska's complex for 2-7 h gives I [R = Ph; X = (PhCH2O2C)2C] in 99% yield. The crystal structure of the chloroform solvate of the iridium biphosphine Ir(1,5-COD)(Ph2PCH2CH2CH2PPh2)Cl2 [Ir(COD)(dppp)Cl2·CHCl3] was detd.
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  (c) Lee, S. I.; Son, S. U.; Choi, M. R.; Chung, Y. K.; Lee, S.-G. Co/C-catalyzed tandem carbocyclization reaction of 1,6-diynes. Tetrahedron Lett. 2003, 44, 4705– 4709, DOI: 10.1016/S0040-4039(03)01053-0
  11c
  Co/C-catalyzed tandem carbocyclization reaction of 1,6-diynes
  Lee, Sang Ick; Son, Seung Uk; Choi, Mi Ra; Chung, Young Keun; Lee, Sueg-Geun
  Tetrahedron Letters (2003), 44 (25), 4705-4709CODEN: TELEAY; ISSN:0040-4039. (Elsevier Science Ltd.)
  Cobalt on charcoal (Co/C) can be used as a catalyst in the tandem carbocycloaddn. reaction of 1,6-diynes and carbon monoxide. The reaction products, e.g., I and II, depend on the reaction temp., the position of functional groups, and the substrate itself.
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12. 12
  (a) Yamamoto, Y.; Miyabe, Y.; Itoh, K. Synthesis of a Dinuclear Ruthenabicyclic Complex and Its Ligand-Substitution Reactions. Eur. J. Inorg. Chem. 2004, 3651– 3661, DOI: 10.1002/ejic.200400128
  12a
  Synthesis of a dinuclear ruthenabicyclic complex and its ligand-substitution reactions
  Yamamoto, Yoshihiko; Miyabe, Yumiko; Itoh, Kenji
  European Journal of Inorganic Chemistry (2004), (18), 3651-3661CODEN: EJICFO; ISSN:1434-1948. (Wiley-VCH Verlag GmbH & Co. KGaA)
  Binuclear η5-dihydrofurano-ruthenacyclopentadiene ruthenium half-sandwich complexes I were prepd. by coupling of bis-propargyl ether O(CH2C≡CCO2Me)2 with Ru3(CO)12. Reaction of Ru3(CO)12 with O(CH2C≡CCO2Me)2 gave I, L1, L2, L3, L4 = CO (3a), ligand substitution with Me3NO gave trimethylamine complex (12, shown as I, L1 = Me3N, L2, L3, L4 = CO). Phosphines react with 12 giving products of mono- and di-substitution, [13a-c, shown as I, L2, L3, L4 = CO, L1 = PPh3, monodentate Ph2PCH2CH2PPh2 and Ph2P(2-Py); 14, L3-L4 = dppm-P,P', L1, L2 = CO; 15b,c; L1-L2 = dppe-P,P', Ph2P(2-Py)-P,N, L3, L3 = CO]. When a phenyl-substituted diyne O(CH2C≡CPh)2 was employed, a cyclopentadienone complex was formed together with the expected dinuclear ruthenacycle complex. In contrast, O(CH2C≡CTMS)2 gave the corresponding cyclopentadienone complex as the only product. The dinuclear mono(amine)ruthenacycle complex also reacted with di-Me butynedioate (DMAD) in refluxing THF to afford a novel μ-η2-alkyne complex [16, shown as I, L3-L4 = C(CO2Me):C(CO2Me)] together with the [2+2+2] cycloadduct between the diyne and DMAD. The highly electron-deficient character of DMAD is imperative for the formation of the μ-alkyne complex. Me propiolate and diphenylacetylene gave no corresponding μ-alkyne complexes.
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  (b) Kim, M.-S.; Lee, J. W.; Lee, J. E.; Kang, J. Synthesis of Enantiopure Ruthenium Tricarbonyl Complexes of a Bicyclic Cyclopentadienone Derivative. Eur. J. Inorg. Chem. 2008, 2008, 2510– 2513, DOI: 10.1002/ejic.200800174
  There is no corresponding record for this reference.
  (c) Sato, H.; Bender, M.; Chen, W.; Krische, M. J. Diols, α-Ketols, and Diones as 2_2π Components in [2 + 2+2] Cycloadditions of 1,6-Diynes via Ruthenium(0)-Catalyzed Transfer Hydrogenation. J. Am. Chem. Soc. 2016, 138, 16244– 16247, DOI: 10.1021/jacs.6b11746
  12c
  Diols, α-Ketols, and Diones as 22π Components in [2+2+2] Cycloadditions of 1,6-Diynes via Ruthenium(0)-Catalyzed Transfer Hydrogenation
  Sato, Hiroki; Bender, Matthias; Chen, Weijie; Krische, Michael J.
  Journal of the American Chemical Society (2016), 138 (50), 16244-16247CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
  The first use of vicinal diols, ketols, or diones as 22π components in metal-catalyzed [2+2+2] cycloaddn. is described. Using ruthenium(0) catalysts, 1,6-diynes form ruthenacyclopentadienes that engage transient diones in successive carbonyl addn. Transfer hydrogenolysis of the resulting ruthenium(II) diolate mediated by the diol or ketol reactant releases the cycloadduct with regeneration of ruthenium(0) and the requisite dione.
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  (d) Yamamoto, Y.; Yamashita, K.; Nakamura, M. Synthesis of Organometallic Analogues of Spirocyclic C-Arylribosides. Organometallics 2010, 29, 1472– 1478, DOI: 10.1021/om100043f
  12d
  Synthesis of Organometallic Analogues of Spirocyclic C-Arylribosides
  Yamamoto, Yoshihiko; Yamashita, Ken; Nakamura, Mitsutaka
  Organometallics (2010), 29 (6), 1472-1478CODEN: ORGND7; ISSN:0276-7333. (American Chemical Society)
  Spirocyclic C-riboside/ruthenium cyclopentadienone complex hybrid mols. were synthesized from silyldiynes, which were derived from the protected γ-ribonolactone and Ru3(CO)12. The structure and stereochem. of the obtained complexes were unambiguously confirmed by x-ray crystallog. The catalytic activity of selected complexes was tested in the hydrogenation of acetophenone and ruthenium hydride species were obsd. by 1H NMR spectroscopy.
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13. 13
  (a) Casey, C. P.; Andrews, M. A.; Rinz, J. E. Rhenium formyl and carboxy complexes derived from the cyclopentadienyl(dicarbonyl)nitrosylrhenium(1+) cation: models for the Fischer–Tropsch and water gas shift reactions. J. Am. Chem. Soc. 1979, 101, 741– 743, DOI: 10.1021/ja00497a045
  13a
  Rhenium formyl and carboxy complexes derived from the cyclopentadienyl(dicarbonyl)nitrosylrhenium(1+) cation: models for the Fischer-Tropsch and water gas shift reactions
  Casey, Charles P.; Andrews, Mark A.; Rinz, James E.
  Journal of the American Chemical Society (1979), 101 (3), 741-3CODEN: JACSAT; ISSN:0002-7863.
  The reaction of (C5H5)Re(CO)2(NO)+PF6- with K+ HB[OCHMe2]3- in THF gives (C5H5)Re(CO)(NO)(CHO) (I), a neutral transition metal formyl complex. Dil. solns. of I gradually decomp. to give (C5H5)Re(CO)(NO)(H). Redn. of I with BH3.THF yields (C5H5)Re(CO)(NO)(Me) while redn. of I with Li+ HBEt3- gives (C5H5)Re(NO)(CHO)2-, the first bis formyl metal complex. Reaction of (C5H5)Re(CO)2(NO)+PF6- with NaOH in water-ether gives the carboxy complex (C5H5)Re(CO)(NO)(CO2H) which reacts with CF3CO2H to reform the starting cation. Treatment of the carboxy complex with Et3N converts it to the hydride (C5H5)Re(CO)(NO)(H). The reaction of (C5H5)Re(CO)2(NO)+PF6- with NaBH4 in benzene-water yields formyl complex I as the major product, not (C5H5)Re(CO)(NO)(CH2OH) as previously reported.
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  (b) Nicholas, K. M. Possible intermediacy of hydrocarbyne complexes in carbon monoxide reduction. Organometallics 1982, 1, 1713– 1715, DOI: 10.1021/om00072a031
  13b
  Possible intermediacy of hydrocarbyne complexes in carbon monoxide reduction
  Nicholas, K. M.
  Organometallics (1982), 1 (12), 1713-15CODEN: ORGND7; ISSN:0276-7333.
  Thermochem. data, modified EHMO calcns., and reactivity and kinetic data suggest that hydroxycarbyne complexes may be important intermediates in homogeneous transition-metal-catalyzed CO redn.
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  (c) Fu, X.; Wayland, B. B. Thermodynamics of Rhodium Hydride Reactions with CO, Aldehydes, and Olefins in Water: Organo-Rhodium Porphyrin Bond Dissociation Free Energies. J. Am. Chem. Soc. 2005, 127, 16460– 16467, DOI: 10.1021/ja054548n
  13c
  Thermodynamics of Rhodium Hydride Reactions with CO, Aldehydes, and Olefins in Water: Organo-Rhodium Porphyrin Bond Dissociation Free Energies
  Fu, Xuefeng; Wayland, Bradford B.
  Journal of the American Chemical Society (2005), 127 (47), 16460-16467CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
  Tetra(p-sulfonato-phenyl) porphyrin Rh hydride ([(TSPP)Rh-D(D2O)]-4) (1) reacts in H2O (D2O) with CO, aldehydes, and olefins to produce metallo formyl, α-hydroxyalkyl, and alkyl complexes, resp. The hydride complex (1) functions as a weak acid in D2O and partially dissocs. into a Rh(I) complex ([(TSPP)RhI(D2O)]-5) and a proton (D+). Fast substrate reactions of 1 in D2O compared to reactions of Rh porphyrin hydride ((por)Rh-H) in benzene are ascribed to aq. media promoting formation of ions and supporting ionic reaction pathways. The regioselectivity for addn. of 1 to olefins is predominantly anti-Markovnikov in acidic D2O and exclusively anti-Markovnikov in basic D2O. The range of accessible equil. thermodn. measurements for Rh hydride substrate reactions is substantially increased in H2O compared to that in org. media through exploiting the H ion dependence for the equil. distribution of species in aq. media. Thermodn. measurements are reported for reactions of a Rh porphyrin hydride in H2O with each of the substrates, including CO, H2CO, CH3CHO, CH2:CH2, and sets of aldehydes and olefins. Reactions of Rh porphyrin hydrides with CO and aldehydes have nearly equal free-energy changes in H2O and benzene, but alkene reactions that form hydrophobic alkyl groups are substantially less favorable in H2O than in benzene. Bond dissocn. free energies in H2O are derived from thermodn. results for (TSPP)Rh-organo complexes in aq. soln. for Rh-CDO, Rh-CH(R)OD, and Rh-CH2CH(D)R units and are compared with related values detd. in benzene.
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  (d) Imler, G. H.; Zdilla, M. J.; Wayland, B. B. Equilibrium Thermodynamics To Form a Rhodium Formyl Complex from Reactions of CO and H₂: Metal σ Donor Activation of CO. J. Am. Chem. Soc. 2014, 136, 5856– 5859, DOI: 10.1021/ja501173d
  13d
  Equilibrium Thermodynamics To Form a Rhodium Formyl Complex from Reactions of CO and H2: Metal σ Donor Activation of CO
  Imler, Gregory H.; Zdilla, Michael J.; Wayland, Bradford B.
  Journal of the American Chemical Society (2014), 136 (16), 5856-5859CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
  A Rh(II) dibenzotetramethylaza[14]annulene dimer ([(tmtaa)Rh]2) (1) reacts with CO and H2 in toluene and pyridine to form equil. distributions with hydride and formyl complexes ((tmtaa)Rh-H (2); (tmtaa)Rh-C(O)H (3)). The Rh formyl complex ((tmtaa)Rh-C(O)H) was isolated under a CO/H2 atmosphere, and the mol. structure was detd. by x-ray diffraction. Equil. consts. were evaluated for reactions of (tmtaa)Rh-H with CO to produce formyl complexes in toluene (K2(298 K)(tol) = 10.8 (1.0) × 103) and pyridine (K2(298 K)(py) = 2.2 (0.2) × 103). Reactions of 1 and 2 in toluene and pyridine are discussed in the context of alternative radical and ionic pathways. The five-coordinate 18-electron Rh(I) complex ([(py)(tmtaa)Rh(I)]-) is proposed to function as a nucleophile toward CO to give a two-electron activated bent Rh-CO unit. Results from DFT calcns. on the (tmtaa)Rh system correlate well with exptl. observations. Reactions of 1 with CO and H2 suggest metal catalyst design features to reduce the activation barriers for homogeneous CO hydrogenation.
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  (e) Teets, T. S.; Labinger, J. A.; Bercaw, J. E. Guanidine-Functionalized Rhenium Cyclopentadienyl Carbonyl Complexes: Synthesis and Cooperative Activation of H–H and O–H Bonds. Organometallics 2014, 33, 4107– 4117, DOI: 10.1021/om500650b
  13e
  Guanidine-functionalized rhenium cyclopentadienyl carbonyl complexes: synthesis and cooperative activation of H-H and O-H bonds
  Teets, Thomas S.; Labinger, Jay A.; Bercaw, John E.
  Organometallics (2014), 33 (15), 4107-4117CODEN: ORGND7; ISSN:0276-7333. (American Chemical Society)
  Catalytic reactions utilizing carbon monoxide as a substrate are numerous, and they typically involve selective functionalization of a metal-bound CO. We have developed Group 7 carbonyl complexes where secondary coordination sphere, Lewis acidic functionalities can assist in the activation of substrate mols., mainly in the context of syngas conversion. This work describes a new class of cyclopentadienyl (Cp) rhenium carbonyl compds. of the type [Re(η5-C5H4DMEG)(CO)3-n(NO)n]n (DMEG = dimethylethyleneguanidine or 1,3-dimethylimidazolidin-2-imino, n = 0, 1), where a tethered guanidine base is appended to the Cp ring to participate in cooperative substrate activation with the electrophilic carbonyl. A reliable synthetic route for these complexes is presented, with crystallog. characterization of the free-base and protonated forms for both the carbonyl and mixed carbonyl-nitrosyl complexes. The latter are employed as platforms to study heterolytic H-H and O-H bond cleavage reactions that result in nucleophilic CO functionalization. The corresponding formyl complex is prepd. by hydride transfer, and by measuring its hydricity (ΔG°H-) and pKa of the protonated base, the free energy of H2 cleavage is found to be +3.3(6) kcal/mol. The activation of methanol to form methoxycarbonyl complexes is found to be more favorable, with ΔG° ≈ 0 for the intramol. addn. of methanol to the guanidine-appended carbonyl complex. A detailed thermodn. study is described for both the intramol. methanol activation reaction and related intermol. reactions with external bases. The results highlight some tangible thermodn. benefits of tethering the base in the secondary coordination sphere.
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  (f) Wiedner, E. S.; Appel, A. M. Thermochemical Insight into the Reduction of CO to CH₃OH with [Re(CO)]⁺ and [Mn(CO)]⁺ Complexes. J. Am. Chem. Soc. 2014, 136, 8661– 8668, DOI: 10.1021/ja502316e
  13f
  Thermochemical Insight into the Reduction of CO to CH3OH with [Re(CO)]+ and [Mn(CO)]+ Complexes
  Wiedner, Eric S.; Appel, Aaron M.
  Journal of the American Chemical Society (2014), 136 (24), 8661-8668CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
  To gain insight into thermodn. barriers for redn. of CO into CH3OH, free energies for redn. of [CpRe(PPh3)(NO)(CO)]+ into CpRe(PPh3)(NO)(CH2OH) have been detd. from exptl. measurements. Using model complexes, the free energies for the transfer of H+, H-, and e- have been detd. A pKa of 10.6 was estd. for [CpRe(PPh3)(NO)(CHOH)]+ by measuring the pKa for the analogous [CpRe(PPh3)(NO)(CMeOH)]+. The hydride donor ability (ΔG°H-) of CpRe(PPh3)(NO)(CH2OH) was estd. to be 58.0 kcal mol-1, based on calorimetry measurements of the hydride-transfer reaction between CpRe(PPh3)(NO)(CHO) and [CpRe(PPh3)(NO)(CHOMe)]+ to generate the methylated analog, CpRe(PPh3)(NO)(CH2OMe). Cyclic voltammograms recorded on CpRe(PPh3)(NO)(CMeO), CpRe(PPh3)(NO)(CH2OMe), and [CpRe(PPh3)(NO)(CHOMe)]+ displayed either a quasireversible oxidn. (neutral species) or redn. (cationic species). These potentials were used as ests. for the oxidn. of CpRe(PPh3)(NO)(CHO) or CpRe(PPh3)(NO)(CH2OH) or the redn. of [CpRe(PPh3)(NO)(CHOH)]+. Combination of the thermodn. data permits construction of three-dimensional free energy landscapes under varying conditions of pH and PH2. The free energy for H2 addn. (ΔG°H2) to [CpRe(PPh3)(NO)(CO)]+ (+15 kcal mol-1) was identified as the most significant thermodn. impediment for the redn. of CO. DFT computations on a series of [CpXM(L)(NO)(CO)]+ (M = Re, Mn) complexes indicate that ΔG°H2 can be varied by 11 kcal mol-1 through variation of both the ancillary ligands and the metal.
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14. 14
  Churchill, M. R.; Wasserman, H. J.; Holmes, S. J.; Schrock, R. R. Coupling of methylidyne and carbonyl ligands on tungsten. Crystal structure of W(η²-HC≡COAlCl₃)(CO)(PMe₃)₃Cl. Organometallics 1982, 1, 766– 768, DOI: 10.1021/om00065a022
  14
  Coupling of methylidyne and carbonyl ligands on tungsten. Crystal structure of W(η2-HC≡COAlCl3)(CO)(PMe3)3Cl
  Churchill, Melvyn Rowen; Wasserman, Harvey J.; Holmes, S. J.; Schrock, R. R.
  Organometallics (1982), 1 (5), 766-8CODEN: ORGND7; ISSN:0276-7333.
  (Me3P)4W(CH)Cl reacts with CO in the presence of AlX3 (X = Me, Cl) to give complexes (Me3P)3W(η2-HC≡COAlX3)(CO)Cl (I). Single crystals of I (X = Cl) are monoclinic, space group P21/c. The essentially planar HC≡COAl system is best regarded as a coordinated acetylene deriv. The role of AlX3 is postulated to be 2-fold, i.e., removal of 1 of the Me3P ligands and activation of either the methylidyne or CO ligand toward the coupling reaction.
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15. 15
  Chatani, N.; Shinohara, M.; Ikeda, S.; Murai, S. Reductive Oligomerization of Carbon Monoxide by Rhodium-Catalyzed Reaction with Hydrosilanes. J. Am. Chem. Soc. 1997, 119, 4303– 4304, DOI: 10.1021/ja9631561
  15
  Reductive Oligomerization of Carbon Monoxide by Rhodium-Catalyzed Reaction with Hydrosilanes
  Chatani, Naoto; Shinohara, Masaaki; Ikeda, Shin-ichi; Murai, Shinji
  Journal of the American Chemical Society (1997), 119 (18), 4303-4304CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)
  The reaction of CO with HSiEt2Me at 140° in the presence of [RhCl2(CO)2]2/Et3N in C6H6 gave MeEt2SiOSiEt2Me as the main product (31% yield) along with reductive coupling of CO which gave diethylmethylsiloxymethane (I), 1,2-bis(diethylmethylsiloxy)ethylene (II), and 1,2,3-tris(diethylmethoxylsiloxy)propylene (III). The reaction of CO with with HSiMe2Ph gave 1,2-bis(dimethylphenylsiloxy)ethylene in yields as high as 62%. The key intermediates were a carbyne-metal complex and dioxyacetylene-metal complex. The reaction of paraformaldehyde with HSiEt2Me and CO in the presence of [RhCl(CO)2]2/Et3N for 1 day gave MeEt2SiOSiEt2Me, I (1%), II (10%), and III (5%), in yields comparable to those obsd. for reactions without paraformaldehyde.
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- CCDC: 2010656
Supporting Information
Supporting Information
The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.orglett.0c02349.
- Experimental details and NMR spectra (PDF)
- ol0c02349_si_001.pdf (2.44 MB)
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CCDC 2010656 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

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Ru₃(CO)₁₂-Catalyzed Reaction of 1,6-Diynes, Carbon Monoxide, and Water via the Reductive Coupling of Carbon Monoxide
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Ru₃(CO)₁₂-Catalyzed Reaction of 1,6-Diynes, Carbon Monoxide, and Water via the Reductive Coupling of Carbon Monoxide
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