Synthesis of 1,2,4‐triazole, 1,2,4‐triazolo[3,4‐b][1,3,4]thiadiazole and 1,2,4‐triazolo[3,4‐b][1,3,4]thiadiazine derivatives of benzotriazole

A novel series of 1‐(1‐carbonylmethyl‐1H‐benzotriazole) thiosemicarbazides 3a‐e was synthesized and then cyclized with sodium hydroxide to afford 1‐(4‐substituted‐4H‐1,2,4‐triazole‐3‐thion‐5‐yl)methyl‐1H‐benzotriazoles 4a‐e, which were alkylated with ethyl iodide to l‐(3‐ethylthio‐4‐substituted‐4H‐1,2,4‐triazol‐5‐yl)‐methyl‐1H‐benzotriazoles 5b‐e. The reaction of 1H‐benzotriazol‐1‐acetic acid hydrazide (2) with carbon disulphide and potassium hydroxide followed by hydrazine hydrate gave 1‐(4‐amino‐4H‐1,2,4‐triazole‐3‐thion‐5‐yl)methyl‐1H‐benzotriazole (6). Its subsequent condensation with carboxylic acids in the presence of phosphorus oxychloride or with phenacyl bromides afforded two series of fused heterocycles namely; 6‐substituted‐3‐[1‐(1H‐benzotriazole)methyl]‐1,2,4‐triazolo[3,4‐b][1,3,4]thiadiazoles 7a‐e and 6‐substituted phenyl‐3‐[1‐(1H‐benzotriazole)methyl]‐7H‐1,2,4‐triazolo[3,4‐b][1,3,4]thiadiazines 8a‐e respectively. The structure of the newly synthesized compounds was elucidated by elemental analyses, ir and nmr spectra.