Bis(α‐bromo ketones): Versatile Precursors for Novel Bis( s ‐triazolo[3,4‐ b ][1,3,4]thiadiazines) and Bis( as ‐triazino[3,4‐ b ][1,3,4]thiadiazines)

A synthesis of bis(α‐bromo ketones) 5a‐c and 6b,c was accomplished by the reaction of bis(acetophenones) 3a‐c and 4b,c with N ‐bromosuccinimide in the presence of p ‐toluenesulfonic acid ( p ‐TsOH). Treatment of 5a‐c and 6b,c with each of 4‐amino‐3‐mercapto‐1,2,4‐triazoles 9a,b and 4‐amino‐6‐phenyl‐3‐mercapto‐1,2,4‐triazin‐5(4 H )‐ones 13 in refluxing ethanol afforded the novel bis( s ‐triazolo[3,4‐ b ][1,3,4]thiadiazines) 10a‐d and 11a‐c as well as bis( as ‐triazino[3,4‐ b ][1,3,4]thiadiazines) 14a‐c and 15 , respectively, in good yields. Compounds 11b and 11c underwent NaBH 4 reduction in methanol to give the target 1,ω‐bis{4‐(6,7‐dihydro‐3‐substituted‐5 H ‐1,2,4‐triazolo[3,4‐ b ][1,3,4]thiadiazin‐6‐yl)phenoxy}butanes 12a and 12b in 42 and 46% yields, respectively.