Regio- and stereospecific cleavage of α,β-epoxysilanes with lithium phenylsulfide

Trimethyl- or dimethylphenylsilylepoxides react with lithium phenylsulfide to give regio- and stereodefined vinyl sulfides resulting from α-ring opening and Peterson elimination. When the epoxide bears the bulky tert-butyldiphenylsilyl group the reaction is more puzzling. Depending on the β-substitution and the presence of aluminium chloride, we obtained silyl enol ethers, α-silylaldehydes or α-hydroxy-β-phenylthiosilanes, all resulting from β-opening.