Difluoroacetic Acid as a New Reagent for Direct C-H Difluoromethylation of Heteroaromatic Compounds

A technically simple procedure for direct C-H difluoromethylation of heteroaromatic compounds using off-the-shelf difluoroacetic acid as the difluoromethylating reagent has been developed. Mono-difluoromethylation versus bis-difluoromethylation is controlled as the result of the reaction temperature. The reactions described here enable access to the late-stage C-H mono- and bis-difluoromethylation for preparation of tool compounds for chemical biology and provide access to this hitherto untapped substituent for drug discovery.