Silyl enol ethers Chlorotrimethylsilane-Zinc

The conjugate addition of bis(iodozincio)methane to -unsaturated carbonyl compound gives y-zincio substituted enolate. As shown in equation 31, bis(iodozincio)methane reacts with. v-cis a,/3-unsaturated ketone in the presence of chlorotrimethylsilane to afford the silyl enol ether carrying a C—Zn bond. These zinc-substituted silyl enolates can be used for further coupling reactions (equation 32)54. 

A derivatization of zinc enolates like 418, formed in a copper-catalyzed conjugate addition, by trapping as silyl enol ethers 419 was reported by Alexakis group [209]. The addition occurred in very high enantioselectivity when mediated by phosphoramidite 417 or related ligands. Remarkably, the selectivity was distinctly lower when chlorotrimethylsilane was present from the beginning. Therefore,... 

The newest techniques employ silylation. Even the anions of saturated butenolides afford the enol ester on reaction with chlorotrimethylsilane91 applied to a butenolide the method readily supplies a 2-silyloxyfuran. Such ethers are even more easily procured by allowing a butenolide to react with chlorotrimethylsilane in the presence of triethylamine and zinc chloride but for reasons that remain unclear, acetonitrile is the only satisfactory solvent.92 A typical transformation of 2-trimethylsilyloxyfuran is shown in Scheme 19. 

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