Synthesis of Benzo-Fused Cyclic Ketones via Metal-Free Ring Expansion of Cyclopropanols Enabled by Proton-Coupled Electron Transfer.

The metal-free ring expansion of cyclopropanols containing a pendant styrene moiety was successfully achieved using a proton-coupled electron transfer enabled by an organic photoredox catalyst. Through this, variants of 1-tetralone and 1-benzosuberone bearing a substituent at the benzylic position were selectively obtained through the regioselective ring closure of alkyl radical intermediates depending on the substitution pattern of the alkene moiety.