Microwave‐assisted synthesis of some 1,2,4‐triazol‐5‐one derivatives

A series of 3‐alkyl(aryl)‐4‐( p ‐hydroxy‐phenyl)‐4,5‐dihydro‐1 H ‐1,2,4‐triazol‐5‐ones 2 were obtained from the reaction of alkyl (aryl) ester ethoxycarbonyl hydrazones 1 with p ‐hydroxy aniline. The reaction of 1 with 1,4‐diamino benzene (1:1) to afford 3‐alkyl(aryl)‐4‐( p ‐aminophenyl)‐4,5‐dihydro‐1 H ‐1,2,4‐triazol‐5‐ones 3 . The reaction of 3 with benzaldehyde gave 3‐alkyl(aryl)‐4‐(4′‐benzilidenamino)‐4,5‐dihydro‐1 H ‐1,2,4‐triazol‐5‐ones 4 . All of the above reactions occurred under microwave heating and conventional methods. Their structures were confirmed by 1 H NMR, 13 C NMR, IR, and elemental analyses.