Photoredox-Catalyzed 1,4-Peroxidation–Sulfonylation of Enynones: A Three-Component Radical Coupling Approach for the Synthesis of Highly Functionalized Allenes

An Eosin Y-catalyzed visible light-promoted 1,4-peroxidation–sulfonylation
of enynones was achieved to give tetrasubstituted allenes. The photoredox
catalysis of Eosin Y allowed the concomitant formation of peroxy and
sulfonyl radicals, where the preferential peroxy radical addition
to the alkene moiety of enynones resulted in the subsequent α-keto
radical–sulfonyl radical cross couplings. The developed photoredox
catalysis of Eosin Y demonstrates a regioselective 1,4-diradical addition
strategy, opening up a new possibility of diradical functionalization
of conjugate systems.