Radical Cation Cycloadditions Using Cleavable Redox Auxiliaries.

The incorporation of an easily oxidized arylsulfide moiety facilitates the photocatalytic generation of alkene radical cations that undergo a variety of cycloaddition reactions with electron-rich reaction partners. The sulfide moiety can subsequently be reductively cleaved in a traceless fashion, affording products that are not otherwise directly accessible using photoredox catalysis. This approach constitutes a novel oxidative "redox auxiliary" strategy that offers a practical means to circumvent a fundamental thermodynamic limitation facing photoredox reactions.