Carbocation Generation by Organophotoredox Catalysis

抄録

Carbocations have gained much attention as fundamental and reactive chemical species, enabling the construction of sterically hindered and complex molecules. Conventionally, the generation of a carbocation requires the use of strong acid, which limits their applications to the synthesis of highly functionalized molecules. Herein, we present a visible light-mediated, organophotoredox, radical-polar crossover catalytic method for non-acidic generation of carbocations. Under blue light irradiation, a phenothiazine based- organophotoredox catalyst converts an alkyl electrophile to the corresponding alkylsulfonium species via sequential single electron transfer events. The generated alkylsulfonium species acts as a carbocation equivalent, and reacts with a broad range of nucleophiles. By taking advantage of the characteristics of radical-mediated reactions, a radical relay type, vicinal difunctionalization of alkenes has also been accomplished.