Sensitized photooxygenations of a few sydnones and azomethine imines have been studied. The photooxygenation of 3,4-diphenylsydnone (lb), for example, gave a 25% yield of a,d-dibenzoylphenylhydrazine (16b) as the only isolable product, whereas the photooxygenation of 4-phenyl-3-p-tolylsydnone (lc) resulted in the formation of a mixture of products containing ,/3-dibenzoyl-p-tolylhydrazine (16c, 8%) and 4,5-diphenyl-2-p-tolyl-1,2,3-triazole (8c, 8%). Under analogous conditions, 3-phenyl-4-p-tolylsydnone (Id) gave a mixture of products consisting of , -di-p-toluylphenylhydrazine (16d, 10%) and 2-phenyl-4,5-di-p-tolyl-l,2,3-triazole (8d, 1%). Irradiation of Id in either benzene or methanol and in the absence of any oxygen gave the triazole 8d as the only isolable product. Similarly, the photooxygenation of 3-methyl-4-phenylsydnone (le) in methanol gave a mixture of benzoic acid (12b, 10%) and ,ß-dibenzoylmethylhydrazine (16e, 5%), whereas irradiation of le in benzene gave a 10% yield of 4-methyl-2-phenyl-A2-l,3,4-oxadiazolin-5-one (5e). The photooxygenation of an azomethine imine, namely, C-biphenylene-7Va-(4-chlorophenyl)-iV8-cyanoazomethine imine (19), gave a 78% yield of 9-fluorenone (21). Reasonable mechanisms have been suggested for the formation of the various products in these reactions.
