Synthesis of heterocycles. Part VII Synthesis and antimicrobial activity of some 7 H‐s ‐triazolo[3,4‐ b ][1,3,4]thiadiazine and s ‐triazolo[3,4‐ b ][1,3,4]thiadiazole derivatives

The cyclization of 4‐amino‐5‐aryl‐3‐cyanomethylthio‐1,2,4‐triazoles II in the presence of concentrated sulfuric acid yields 7 H ‐6‐amino‐ s ‐triazolo[3,4‐ b ][1,3,4]thiadiazines III . Cyclization of 4‐amino‐5‐aryl‐1,2,4‐tria‐zole‐3‐thiones I with phenacyl chloride yields 7 H ‐3‐aryl‐6‐phenyl‐ s ‐triazolo[3,4‐ b ][1,3,4]thiadiazines IV . Similarly, compounds I condensed with cyanogen bromide, phenyl isothiocyanate and carbon disulfide to give the corresponding cyclized products 6‐amino‐3‐aryl‐ s ‐triazolo[3,4‐ b ][1,3,4]thiadiazoles V , 3‐aryl‐6‐phenyl‐amino‐ s ‐triazolo[3,4‐ b ][1,3,4]thiadiazoles VI and 3‐aryl‐striazolo[3,4‐ b ][1,3,4]thiadiazol‐6(5 H )thiones VII , respectively. Also in the presence of phosphoryl chloride, compounds I underwent cyclization with monocarbo‐xylic acids and oxalic acid to 3,6‐diaryl‐ s ‐triazolo[3,4‐ b ][1,3,4]thiadiazole VIII and 6,6′‐bis(3‐aryl‐ s ‐triazolo‐[3,4‐ b ][1,3,4]thiadiazoles) IX . The above compounds were screened for their antimicrobial activity.