Dilithium cyanobis(dimethyl(phenyl)silyl)cuprate(2-)

Physical properties

relatively stable reagent at rt; usually prepared in situ at 0°C.

The Uses of Dilithium cyanobis(dimethyl(phenyl)silyl)cuprate(2-)

DilithiumCyanobis(dimethylphenylsilyl)- cuprate is a higher-order copper reagent for transfer of a dimethylphenylsilyl group to enones, allenes, alkynes, epoxides, and alkyl halides.
The silylcuprate reacts with allylic acetates directly to give allylsilanes (eqs 16–18). Bissecondary allylic acetates are apt to form both regioisomers, but some control of the regiochemistry is possible, using a cis double bond, which encourages reaction with allylic shift, especially when the silyl group is delivered to the less-hindered end of the allylic system (eq 16).An alternative protocol, assembling a mixed silylcuprate on a carbamate group, is even better at controlling the regioselectivity, usually giving complete allylic shift (eq 17). Tertiary acetates in contrast are well behaved regiochemically, giving only the product with the silyl group at the less-substituted end of the allylic system (eq 18)Allylsilanes have many uses as carbon nucleophiles in organic synthesis.A similar reaction takes place with allylic epoxides.
The acetate reaction (eq 16) and the carbamate alternative (eq 17) are complementary in their stereochemistry, the former taking place stereospecifically anti and the latter stereospecifically syn.

Preparation

prepared by adding 0.5 equiv of dry copper(I) cyanide to dimethylphenylsilyllithium in THF (eq 1), which in turn is generated from chlorodimethylphenylsilane and lithium metal. Analogous bis(trimethylsilyl)cyanocuprates are prepared in a similar manner.