Photochemical studies on heterocyclic compounds. Part I. Rearrangements of pyrazolinones and pyrazolidinones

Abstract

2,3-Dimethyl-1-phenyl-3-pyrazolin-5-one (I) undergoes a transposition of its ring atoms to give 1,5-dimethyl-3-phenyl-4-imidazolin-2-one (II) as well as the appropriate N-acetonylphenylcarbamata (IIIa or b) on irradiation in alcohols. Irradiation in acetone gives N-acetonylformanilide (VIII) instead of the carbamate (III). A series of 2-phenyl-pyrazolidin-3-ones (IXa–c), on irradiation, rearranged to 1-anilinoazetidin-2-ones (Xa–c), and gave, as well, cis- and trans-phenylazoalkanoates (XI and XII).