Facile Route for the Synthesis of Pyridazine Derivatives: Unexpected Pathway to Benzothiazole,Benzimidazole, and Triazole Derivatives

4‐Amino‐5‐arylmethylidene‐3‐phenyl‐pyridazin‐6‐ones 7 have been synthesized and reacted with selected nucleophile reagents such as phenyl hydrazine, semicarbazide, semithiocarbazide, cyanoacetohydrazide, 2‐aminothiophenol, and 2‐phenylenediamine in ethanol triethyl‐amine solution. An unexpected 1‐phenyl‐3‐arylaziridene 10, 3‐aryl‐5‐oxo(thio)‐1,2,4‐triazole 21, 4‐amino‐3‐aryl‐6‐hydroxy‐pridazine 27, 2‐arylbenzothiazole 30a–c, and 2‐arylbenzimidazole 30d–f have been obtained, respectively. Also, 2‐aminothiophenol and 2‐phenylenediamine were reacted with N‐phenylmethylidene‐2‐cyanoacetohydrazide 2, affording the new 1,4‐benzodiazepine derivatives 35.