PHOTO-OXYGENATIONS OF SYDNONES AND AZOMETHINE IMINES

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 α,β-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 α,β-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, α,β-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 α,β-dibenzoylmethylhydrazine (16e, 5%), whereas irradiation of le in benzene gave a 10% yield of 4-methyl-2-phenyl-∇2-l, 3, 4-oxadiazolin-5-one (5e). The photooxygenation of an azomethine imine, namely, C-biphenylene-Nα-(4-chlorophenyl)-Nβ-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. © 1979, American Chemical Society. All rights reserved.