The configurational stability of an enantioenriched alpha-thiobenzyllithium derivative and the stereochemical course of its electrophilic substitution reactions; synthesis of enantiomerically pure, tertiary benzylic thiols.

The lithium compound (S)-7, formed by deprotonation of the (S)-S-1-phenylethyl thiocarbamate (S)-10, is configurationally stable at -70 degrees C. Even at elevated temperatures it racemizes only very slowly. It represents the first essentially enantiopure alpha-thiocarbanion derivative and can be utilized in asymmetric synthesis. Most electrophiles (except proton acids) add to (S)-7 with complete stereoinversion. Cleavage of the substitution products leads to practically enantiopure, tertiary 1-phenylalkanethiols.