Synthesis of Aryl Alkyl Sulfides by γ-Addition of Aryl Thiols to Allenoates

Significance

Fu and co-workers have developed a methodology for the synthesis of aryl alkyl sulfides by γ-addition of aryl thiols to allenoates, ­catalyzed by monophosphepine (S)-1. In the proposed mechanism, racemic allenoates undergo de-racemization to the same chiral intermediate A. During the course of a mechanistic study, it was found that the resting state of the catalyst is the phosphine itself, and modest kinetic resolution of the unreacted allene was observed. All the data are consistent with a rate-determining irreversible 1,4-addition of the phosphepine catalyst to allen­oate.