Copper-Catalyzed C-H Difluoroalkylation of Coumarins with Fluoroalkyl Bromides

An efficient method for the copper-catalyzed selective C-H difluoroalkylation of coumarins and with low cost and readily available ethyl bromodifluoroacetate andN-phenyl bromodifluoroacetamide has been reported. This reaction exhibits good functional group tolerance with respect to coumarins and difluoroalkylation reagents, and several redox-sensitive substrates have been successfully C-H difluoroalkylated in good to high yield. This design could further expand the scope to other heteroarenes, including furan, benzofuran, pyrrole, pyridinone, chromenone, indole, and quinolinone. A mechanism involving copper-catalyzed in-situ generation of fluoroalkyl radical is proposed.