Metal-Free Defluorinative Arylation of Trifluoromethyl Alkenes via Photoredox Catalysis

Literature methods to access gem-difluoroalkenes are largely limited to harsh, organometallic-based methods, and known photoredox mediated processes are not amenable to aryl radical addition to trifluoromethyl alkenes. A mild, metal-free, functional group-tolerant method for the preparation of benzylic gem-difluoroalkenes is described. The combination of organic dye photocatalyst and silanol reductant enables halogen atom abstration from (hetero)aryl halides to generate aryl radicals that undergo a defluorinative arylation of α-trifluoromethyl alkenes. A breadth of electronically disparate aryl radicals and α-trifluoromethyl alkenes are effective under the developed conditions, which demonstrates high functional group compatibility and allows access to structures previously untenable under traditional transition metal-mediated methods.