Stereoselective Reaction of α-Sulfinyl Carbanion Derived from Chiral 2-(Trialkylsilyl)ethyl Sulfoxides:  Evidence for a Novel Silicon−Oxygen Interaction

Reactions of α-sulfinyl carbanions, derived from p-tolyl sulfoxides bearing various alkyl groups, with various electrophiles were examined. The reaction of α-sulfinyl carbanions, derived from the β-silylethyl sulfoxides, with ketones or trimethyl phosphate, gave the syn products with high stereoselectivity. Interaction between the silicon in the trialkylsilyl group and the carbonyl oxygen in nucleophiles was postulated to stabilize the transition state, leading preferably to the syn diastereisomers. This novel silicon−oxygen interaction was supported by an MO calculation study using the MOPAC 93/PM3 and the Gaussian 94 Beche3LYP/3-21+G* methods.