Electrochemical Arene Radical Cation Promoted Spirocyclization of Biaryl Ynones: Access to Alkoxylated Spiro[5,5]trienones.

Herein, a novel electrochemical arene radical cation promoted dearomative spirocyclization of biaryl ynones with alcohols is described, providing a conceptually novel transformation mode for producing diverse alkoxylated spiro[5,5]trienones. The catalyst- and chemical-oxidant-free spirocyclization protocol features broad substrate scope and high functional group tolerance. Mechanistic studies reveal that the generation of arene radical cation via anodic single-electron oxidation is crucial, with sequential 6- endo - dig cyclization, dissociation of hemiketal, anodic oxidation, and nucleophilic attack of alcohols.