Photocatalytic Radical Ortho-Dearomative Cyclization: Access to Spiro[4.5]deca-1,7,9-trien-6-ones.

A highly efficient ortho-dearomative cyclization reaction between alkynes and 2-bromo-2-(2-methoxybenzyl)malonate via visible light-induced photoredox catalysis has been reported. In the presence of 1 mol % fac-Ir(ppy)3, a variety of spiro[4.5]deca-1,7,9-trien-6-ones were obtained in moderate to excellent yields under mild conditions. Under the optimized reaction conditions, a sample reaction of 3 mmol scale proceeded smoothly to give the desired products in 84% yield with a low catalyst loading of 0.1 mol %.