Visible-Light-Driven Dearomatization Reaction toward the Formation of Spiro[4.5]deca-1,6,9-trien-8-ones.

A visible-light-driven regioselective dearomative cyclization between 2-benzyl-2-bromomalonate and alkynes under mild conditions leading to the formation of spiro[4,5]decanes has been developed. In the presence of H2O, a variety of 2-benzyl-2-bromomalonates smoothly undergo 5-exo-dig radical dearomative cyclization with alkynes to afford the corresponding spiro[4,5]decanes in moderate to good yield in a step-economical manner under oxidant-free conditions.