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 α-thioenones are formed in the reaction of propargylsulfoxides. The proposed mechanism proceeds via an α-carbonyl gold−carbenoid intermediate formed through gold-promoted oxygen atom transfer from the sulfoxide to the alkyne.