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-(C4F9)-C-n and Ar-(C6F13)-C-n 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.

Automated summary

Site-selective and direct C-F bond transformation of perfluoroalkylarenes was achieved using an iridium photoredox catalyst system with allylic stannanes. The defluoroallylation process exclusively occurs at the benzylic position through perfluoroalkyl radicals generated by a single-electron transfer. Different perfluoroalkyl groups are applicable, and the utility of this reaction was demonstrated through the synthesis of a specific compound.