Intramolecular photo[4+2]cycloaddition of an enone with a benzene ring

N-Benzoyl-N-benzylcinnamamides 1, N-acetyl-N-(1-benzyl)cinnamamides 3 and N-[(1-benzyl)aminocarbonyl]-N-(1-benzyl)cinnamamides 5 have been irradiated by a high-pressure mercury lamp in the presence of benzil in benzene at room temperature to give 3-azatricyclo[5.2.2.01,5]undeca-8,10-dien-4-ones 2, 4 and 6 with high stereoselectivity. These are the first photo[4+2]cycloadducts of an enone and a benzene ring.