(Trimethylsilyl)ethynylcopper(I)1

[53210-13-2]  · C5H9CuSi  · (Trimethylsilyl)ethynylcopper(I)  · (MW 160.78)

(coupling agent for introduction of the (trimethylsilyl)ethynyl group;2 preparation of mixed cuprates3)

Alternate Name: copper(I) trimethylsilylacetylide.

Physical Data: orange-red unstable solid.

Solubility: sol THF, THF-HMPA mixtures; insol ether.

Preparative Methods: by treatment of Trimethylsilylacetylene with Copper(I) t-Butoxide,2 by addition of CuBr.SMe2 (see Copper(I) Bromide) to a THF solution of Lithium (Trimethylsilyl)acetylide,4 or by treatment of trimethylsilylacetylene with Triethyl Phosphite and Copper(I) Chloride.5

Handling, Storage, and Precautions: best generated in situ and used immediately.2 THF solutions are unstable above -20 °C.2 The solid is unstable, and all such copper(I) acetylides are potentially explosive. Use in a fume hood.

Coupling Agent.

Copper trimethylsilylacetylide is a versatile coupling agent for introduction of the trimethylsilylethynyl group to activated molecules. Due to the instability of the reagent, the Castro coupling reaction cannot be attempted, but additions to acyl chlorides,2 activated amines,6 and terminal (methoxy)iodoallenes have been reported.7 This last reaction proceeds via an SN2 mechanism, and a similar addition has been observed with a-acetoxy alkynes (eq 1) giving allenic alkynes in high yield.8 Coupling between copper TMS-acetylide and 1,2-dichloroalkenes has also been demonstrated.9,10 Coupling of the copper acetylide (generated in situ) to give the biologically important enediyne framework can be achieved using palladium catalysis (eq 2).10

Mixed Organocuprates.

The trimethylsilylethynyl group acts as a nontransferable dummy ligand (see also 1-Pentynylcopper(I)-Hexamethylphosphorous Triamide, 1-Hexynylcopper(I), (3-Methoxy-3-methyl-1-butynyl)copper(I)) when copper trimethylsilylacetylide is converted to a mixed alkyl or vinyl cuprate.3,11,12 In one report, utilization of a mixed cuprate derived from a terminally lithiated allene allows chemoselective conjugate delivery of the allenic moiety to an a,b-unsaturated system (eq 3), which gives a functionalized and versatile enone system on hydrolysis.3 The effects of Chlorotrimethylsilane on such conjugate additions have been studied.11 On using a mixed cuprate derived from combination with n-Butyllithium in the presence of TMSCl, smooth and efficient 1,4-butylation ensues (eq 4).11 The stoichiometry of the TMSCl employed has a marked effect on the reaction profile. Mixed magnesioorganocuprates have also been employed in conjugate addition reactions.12 The highest yields of the corresponding 1,4-addition products are recovered using a stoichiometry of 3:1 Grignard reagent-copper TMS-acetylide.12

Copper Homoenolates.

Magnesium homoenolates, typically generated by addition of Vinylmagnesium Bromide to an acyltrimethylsilane, undergo conjugate addition to enones (eq 5) in the presence of copper trimethylsilylacetylide, giving easy access to 1,6-diketones.4,13 The reaction presumably proceeds via a mixed copper homoenolate, with the trimethylsilylethynyl group acting as a nontransferable ligand.

Related Reagents.

3-Trimethylsilyl-2-propynylcopper(I).


1. (a) Normant, J. F. S 1972, 63. (b) Sladkov, A. M.; Gol'ding, I. R. RCR 1979, 48, 868. (c) Lipshutz, B. H.; Sengupta, S. OR 1992, 41, 135. (d) FF 1977, 6, 148.
2. Logue, M. W.; Moore, G. L. JOC 1975, 40, 131.
3. Matsuoka, R.; Horiguchi, Y.; Kuwajima, I. TL 1987, 28, 1299.
4. Enda, J.; Kuwajima, I. JACS 1985, 107, 5495.
5. Shostakovskii, M. F.; Polyakova, L. A.; Vasil'eva, L. V.; Polyakov, A. I. ZOR 1966, 2, 1899.
6. Boche, G.; Bernheim, M.; Niessner, M. AG(E) 1983, 22, 53.
7. Oostveen, J. M.; Westmijze, H.; Vermeer, P. JOC 1980, 45, 1158.
8. Ruitenberg, K.; Kleijn, H.; Westmijze, H.; Meijer, J.; Vermeer, P. RTC 1982, 101, 405.
9. Rubin, Y.; Diederich, F. JACS 1989, 111, 6870.
10. Vollhardt, K. P. C.; Winn, L. S. TL 1985, 26, 709.
11. Sakata, H.; Kuwajima, I. TL 1987, 28, 5719.
12. Drouin, J.; Rousseau, G. JOM 1985, 289, 223.
13. Enda, J.; Matsutani, T.; Kuwajima, I. TL 1984, 25, 5307.

Graham B. Jones & Brant J. Chapman

Clemson University, SC, USA



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