HFIP-Assisted Single C−F Bond Activation of Trifluoromethyl Ketones using Visible-Light Photoredox Catalysis

Abstract

A visible light photoredox catalytic method for the selective cleavage of single strong C−F bond in trifluoromethyl ketones is reported. Single electron reduction of trifluoromethyl ketones generates difluoromethyl radicals which can be engaged in intermolecular C−C bond formation with N-methyl-N-arylmethacrylamides to furnish fluorine-containing oxindole derivatives in good yields. The reaction shows excellent chemoselectivity with good functional group tolerance under mild conditions. 1,1,1,3,3,3-Hexafluoroisopropanol (HFIP) as a solvent plays a critical role for the selective single C−F bond cleavage. High-level DFT calculations are depicted to shed light on the mechanism.