Regio- and stereoselective tert-butylthiolation of internal alkynes with thioethers initiated and maintained by silylium-ion catalysis

Abstract

A two-component protocol for the regio- and trans-selective addition of aryl tertiary alkyl (especially tert-butyl) thioethers across internal C≡C triple bonds is reported. This carbothiolation is initiated by the catalytic formation of a silylated sulfonium ion as tertiary carbenium ion (tert-butyl cation) source. Competing loss of a proton by β-elimination of that carbenium-ion intermediate and as such a potential hydrothiolation pathway are efficiently suppressed by the substoichiometric addition of an arylsilane as a “proton-into-silylium ion” generator. Through this, the silylium-ion activation is restored, thereby maintaining the carbothiolation pathway. The method enables the synthesis of sterically crowded, fully substituted aryl vinyl sulfides as well as the sulfoxides and sulfones.