Reductive Catalytic Difluorocarbene Transfer via Palladium Catalysis

Abstract

AbstractA palladium‐catalyzed reductive difluorocarbene transfer reaction that tames difluorocarbene to couple with two electrophiles has been developed, representing a new mode of difluorocarbene transfer reaction. The approach uses low‐cost and bulk industrial chemical chlorodifluoromethane (ClCF2H) as the difluorocarbene precursor. It produces a variety of difluoromethylated (hetero)arenes from widely available aryl halides/triflates and proton sources, featuring high functional group tolerance and synthetic convenience without preparing organometallic reagents. Experimental mechanistic studies reveal that an unexpected Pd0/II catalytic cycle is involved in this reductive reaction, wherein the oxidative addition of palladium(0) difluorocarbene ([Pd0(Ln)]=CF2) with aryl electrophile to generate the key intermediate aryldifluoromethylpalladium [ArCF2Pd(Ln)X], followed by reaction with hydroquinone, is responsible for the reductive difluorocarbene transfer.