Gold-Catalyzed Highly Selective Photoredox C(sp2)-H Difluoroalkylation and Perfluoroalkylation of Hydrazones

The first gold-catalyzed photoredox C(sp(2))-H difluoroalkylation and perfluoroalkylation of hydrazones with readily available R-F-Br reagents is reported. The resulting gem-difluoromethylated and perfluoroalkylated hydrazones are highly functionalized, versatile molecules. A mild reduction of the coupling products can efficiently produce gem-difluoromethylated beta-amino phosphonic acids and beta-amino acid derivatives. In mechanistic studies, a difluoroalkyl radical intermediate was detected by an EPR spin-trapping experiment, indicating that a gold-catalyzed radical pathway is operating.