Thermal behaviour of 3-phenyl-1,2,4-oxadiazol-5-ylhydrazines

Abstract

Depending on the substitution on the hydrazine moiety, thermolysis of 3-phenyl-1,2,4-oxadiazol-5-ylhydrazines (1)–(5) gives variable amounts of 1-amino-Δ²-1,2,4-triazolin-5-ones (13) or (17), Δ²- or Δ³-1,2,4-triazolin-5-ones (12), (18), or (19), and the s-triazine (20). A possible mechanism accounting for the products and the effects is discussed. A diradical intermediate and a hydrogen transfer from the reaction medium are suggested on the basis of the effect of benzoyl peroxide on the reaction and on the behaviour of the hydrazines (1)–(4) towards catalytic hydrogenation.