Unified Gold(I/III)-Catalyzed Arylative, Vinylative, and Alkynylative Lactonization via Iminium-Directed Cyclization Enabled by Hemilabile Ligands

We report a unified strategy for the synthesis of functionalized lactones via hemilabile Au(I)/Au(III) redox catalysis. Oxidative addition of aryl, vinyl, or alkynyl iodides to Au(I) is followed by iminium-directed π-activation and lactonization, using AgOTf as a halide scavenger. The method affords 49 lactones under mild, scalable conditions with broad functional group tolerance. Mechanistic studies support iminium and Au(III) intermediates. Moreover, we present a new Au(I)/(III) hemilabile complex that is particularly effective in alkynylation.