Visible-light-induced Mn(0)-catalyzed direct C-3 mono-, di- and perfluoroalkylation reactions of 2H-indazoles

A general and efficient method for visible-light-driven fluoroalkylation, such as difluoromethylphosphonation, difluoroacetamidation, monofluoromethylation, difluoromethylation, and perfluoroalkyalation, of 2H-indazoles using an inexpensive Mn2(CO)10 photocatalyst has been developed. The present methodology affords a new series of C-3 fluoroalkylated 2H-indazole derivatives with wide functional group tolerance in good to excellent yields. Difluoromethylenated indiazoles are also prepared from difluoroester derivatives. Our mechanistic investigations support a radical pathway for the reaction.