Photolysis of acyl azides (1, 10) in diketene was investigated. Irradiation of a mixture of benzoyl azide (1a) and diketene in dichloromethane gave 1-benzoyl-4-hydroxy-3-pyrrolin-2-one (2a) in 17% yield. Similarly, reaction of diketene with p-anisoyl azide (1b), p-toluoyl azide (1c), p-chlorobenzoyl azide (1d) and ethyl azidoformate (10) gave the corresponding pyrrolinones (2b, 2c, 2d, and 11) in 7-22% yields.
