Synthesis and Evaluation of Bioactivity of Thiazolo[3,2‐ b ]‐[1,2,4]‐triazoles and Isomeric Thiazolo[2,3‐ c ]‐[1,2,4]‐triazoles

Synthesis of 2‐( o ‐nitrophenyl)‐6‐arylthiazolo[3,2‐ b ]‐[1,2,4]‐triazoles 4 and its isomer 3‐( o ‐nitrophenyl)‐5‐arylthiazolo[2,3‐ c ]‐[1,2,4]‐triazoles 6 has been achieved starting from the appropriate 1‐( o ‐nitrobenzoyl)‐3‐thiosemicarbazide 1 . Compound 1 on condensation with α‐haloketones gives 2‐( o ‐nitrobenzoyl)hydrazino‐4‐arylthiazole hydrobromide 5 , which, on cyclization with POCl 3 , affords thiazolo[3,2‐ b ]‐[1,2,4]‐triazoles 6 and not the isomeric thiazolo[3,2‐ b ]‐[1,2,4]‐triazoles 4 . This has been established by an unequivocal synthesis of 4 through polyphosphoric acid cyclization of 5‐aroylmethylmercapto‐3‐ o ‐nitrophenyl‐[1,2,4]‐triazole 3 . Compound 3 was synthesized by condensation of α‐haloketones with 5‐mercapto‐3‐( o ‐nitrophenyl)‐[1,2,4]‐triazole 2 , obtained cyclization of 2‐( o ‐nitrobenzoyl)hydrazinecarbothioamide 1 with NaOH. The antibacterial and antifungal activities of some of the compounds have also been evaluated.