Rearrangement of alkynyl sulfoxides catalyzed by gold(I) complexes

A series of gold(I)-catalyzed rearrangement reactions of alkynyl sulfoxides are reported. Homopropargylsulfoxides are rearranged to benzothiepinones or benzothiopines, while alpha-thioenones are formed in the reaction of propargylsulfoxides. The proposed mechanism proceeds via an alpha-carbonyl gold-carbenoid intermediate formed through gold-promoted oxygen atom transfer from the sulfoxide to the alkyne.