Science of Synthesis

Singer, R. D., Science of Synthesis, (2002) 4, 231.

General Introduction

Triorganosilylcopper reagents are important reagents for the formation of Si—C bonds.[‌1‌] In fact, lithium-based (triorganosilyl)cuprates (R3Si)nCuLin-1•LiX (n = 1 or 2, X = Br, I or CN) are perhaps the most widely used reagents for the transfer of R3Si anions to organic substrates. Specifically, dilithium cyanobis(dimethylphenylsilyl)cuprate [(PhMe2Si)2CuCNLi2] is the most widely used triorganosilylcopper reagent in silylcuprations of unsaturated substrates such as acetylenes, allenes, and enones. Less-popular triorganosilylcopper reagents include the bulky dilithium bis(tert-butyldiphenylsilyl)cyanocuprate [(t-BuPh2Si)2CuCNLi2].[‌2‌] In general, reactions using these reagents occur under mild conditions and tolerate most polar functional groups. Triorganosilylcuprate reagents that contain only silyl moieties bonded to the copper are good reagents for the introduction of triorganosilyl groups to organic substrates. However, the fact that not all of the silyl moieties are transferred to the organic substrate when using the homo triorganosilylcuprate reagents (i.e., that contain only triorganosilyl groups bonded to the copper atom) can be viewed as a limitation. To address this drawback mixed alkyl(triorganosilyl)cuprate reagents have been developed.[‌3‌] These reagents have the general formula (R13Si)R2CuLi•LiX, where R2 = organo and SiR13 = SiMe2Ph (most commonly) and selectively transfer their triorganosilyl moiety while generally avoiding transfer of the less-expensive alkyl moiety. The silylcopper reagent lithium cyano(dimethylphenylsilyl)cuprate [PhMe2SiCuCNLi] has also been employed to reduce side product formation and loss of unreacted triorganosilyl anion.[‌3‌]

References