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(alpha-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(4H)-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 NaBH4 reduction in methanol to give the target 1,omega-bis{4-(6,7-dihydro-3-substituted-5H-1,2,4-triazolo[3,4-b][1,3,4]thiadiazin-6-yl)phenoxy}butanes 12a and 12b in 42 and 46% yields, respectively.