Photochemistry of βγ-unsaturated carbonyl compounds. 3,3-Dimethyl-5,5-diphenylpent-4-en-2-one and 2,2-dimethyl-4,4-diphenylbut-3-enal

Abstract

Irradiation of 3,3-dimethyl-5,5-diphenylpent-4-en-2-one (1) resulted in formation of 5-methyl-3,3-diphenylhex-4-en-2-one (3), an allylic rearrangement product arising from the singlet excited state. The product 2,2-dimethyl-3,3-diphenylcyclopropyl methyl ketone (8), was absent from both direct and acetophenone-sensitised irradiations. Irradiation of 2,2-dimethyl-4,4-diphenylbut-3-enal (2) resulted in decarbonylation.