Derivatives of arylhydrazonic acids. Part 2: A facile approach to novel 4,5-dihydro-1H-1,2,4-triazoles via cyclization of amidrazones

Starting from arylhydrazonoyl chlorides, the amide arylhydrazones (amidrazones) were obtained by nucleophilic substitution of the chloride function with ammonia, amines or anilines. Treatment of amidrazones with alkyl ketones under acidic catalysis led generally to 4,5-dihydro-1H-1,2,4-triazoles. In addition, with aldehydes 1H-1,2,4-triazoles or aryl condensed 4,5-dihydro-1H-1,3,4-triazepines were formed depending on substitution pattern of amidrazone moiety. The structures of the new products have been established by 1H and 13C NMR studies.