UC Berkeley

The gem-difluoromethylene functional group is an important motif in medicinal chemistry, and development of new fluoroalkyl-metal systems has been crucial to enable new syntheses of gem-difluoromethylenes. However, well-defined and isolable examples of either nucleophilic RCF₂M or difluorocyclopropenyl transition metal complexes are rare. The Au(I) platform has been useful for the synthesis of isolable transition-metal complexes bearing reactive ligands. Herein we utilize reactions of difluorocarbene with organogold(I) complexes, analogous to reactions of difluorocarbene with organic substrates, to access novel examples of gem-difluoromethylene organometallics. First, difluorocarbene insertion into the R─Au(I) bond of organogold(I) species with free difluorocarbene was demonstrated for the first time, forming alkyl-CF₂-Au(I) and aryl-CF₂-Au(I) species. Second, via a difluorocarbene cycloaddition reaction we isolate for the first time a κ¹-difluorocyclopropenyl-transition metal complex, formed by reaction of alkynylAu(I) complex with free difluorocarbene. Subsequent study of these reaction systems by density functional theory calculations facilitated study of the difluorocarbene insertion reactions, and a comparison of difluorocarbene insertion and cycloaddition pathways in the reaction of difluorocarbene and alkynylAu(I).