1,2,4-TRIAZOLE FUSED HETEROCYCLES .3. PREPARATION OF 1-(1-PHENYLETHENYL)-5-(N-SUBSTITUTED AMINO)-1,2,4-TRIAZOLES AND 4H-1,2,4-TRIAZOLO[1,5-C][1,3,5]OXADIAZINES

The reaction of acetophenone 1-ureidoethylidenehydrazones 6 with a mix ture of triphenylphosphine, carbon tetrachloride, and triethylamine in dichloromethane provides a general route to 1-(1-phenylethenyl)-5-(N- substituted amino)-1,2,4-triazoles 11 via the electrocyclization of th e expected azino carbodiimide intermediates 9 to give the resonance st abilized azomethine imine 10a followed by a proton abstraction from th e methyl group by amide anion. However, the same reaction of benzaldeh yde 1-ureidoethylidenehydrazones 5 was unsuccessful. Under the same co nditions, the reactions of benzaldehyde 1-N-acylureidoethylidenehydraz ones 7 or acetophenone 1-N-acylureidoethylidenehydrazones 8 afforded 4 H-1,2,4-triazolo[1,5-c][1,3,5]oxadiazines 16 or 17 via the zwitterioni c species 15, or a [4+2] intramolecular cycloaddition from the carbodi imide intermediates 14, respectively.