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.