Photolysis of Pyridazin-3-one 1-Imides : Ring Contraction into 3-Pyrrolin-2-one Derivatives

Abstract

Irradiation of pyridazin-3-one 1-ethoxycarbonylimide (9a) resulted in ring contraction to give the azamaleimide (11), whereas the 6-methyl derivative (9b), upon irradiation, afforded the 3-pyrrolin-2-one (12). On the other hand, the photolysis of 2-methylpyridazin-3-one 1-imides (10a, b) gave both azamaleimides (13a, b) and 3-pyrrolin-2-ones (14a, b). The mechanism of this photoinduced ring contraction reaction is discussed.