Chlorotrimethylsilane with enolate anions

The conj ugate addition of lithium dimethylcuprate and other organoeopper reagents to a,/ -unsaturated ketones is a reaction which has had wide application and which has been fairly well studied.6 In order that the positional specificity which has been conferred upon the enolate anions generated by such additions might be maintained, these intermediates have been intercepted with acetic anhydride,6 chlorotrimethylsilane, and diethyl phosphorochloridate.4 8... 

As we saw in section 9.4.B,C, the reaction of an ester such as 623 with LDA, under kinetic control conditions, and subsequent reaction of the enolate anion (624) with chlorotrimethylsilane gives the silyl enol... 

The anion 7 is quite nucleophilic and undergoes exclusive C-alkylation upon reaction with electrophiles including chlorotrimethylsilane °. These reactivity patterns have led to the suggestion that enolates of iron-acyl complexes may be considered to behave similarly to the organic dianion 910- u. 

Silylation of oxoenolate anions generally proceeds at the oxygen atom. So far, the only example of C-silylation is the reaction of the enolate derived from tricyclic taxane ketone 1 with chlorotrimethylsilane. The product 2 is obtained as a single diastereomer the configuration was established by X-ray analysis25. 

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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