Photoredox-Catalyzed C–F Bond Allylation of Perfluoroalkylarenes at the Benzylic Position

Site-selective and direct C–F bond transformation of perfluoroalkylarenes was achieved with allylic stannanes via an iridium photoredox catalyst system. The present defluoroallylation proceeds exclusively at the benzylic position through perfluoroalkyl radicals generated by a single-electron transfer from an excited photoredox catalyst to perfluoroalkylarenes. A variety of perfluoroalkyl groups are applicable: linear perfluoroalkyl-substituted arenes such as Ar– n C4F9 and Ar– n C6F13 and heptafluoroisopropylarenes (Ar–CF­(CF3)2) underwent site-selective defluoroallylation. DFT calculation studies revealed that the in situ generated Bu3SnF traps F– to prevent a retroreaction from the unstable perfluoroalkyl radical intermediate, and the radical intermediate favorably reacts with allylic stannanes. The synthesis of a bis­(trifluoromethyl)­methylene unit containing compound, which is an analog that is useful as a pharmaceutical agent for the prophylaxis or treatment of diabetes and inflammatory diseases, demonstrated the utility of this reaction.