Photochemical Synthesis of 2-Alkylidene-1,3-cyclocalkanediones. Preliminary Communication

Photolysis (λ = 254 nm) of 4-(tert-butyl)-4,6,7,8-tetrahydro-7,7-dimethy-2H-1-benzopyran-2,5(3H)-dione ( 3a ) in t-BuOH affords 2-(2,2-dimethylpropylidene)-5,5-dimethyl-1,3-cyclohexanedione ( 1a ) in 80% yield via homolysis of the lactone O? CO bond and subsequent ketene elimination.