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

A synthesis of novel bis(s‐triazolo[3,4‐b][1,3,4]thiadiazines) 4, 5, 6 in which the triazolothiadiazine is linked to the benzene core through the thiadiazine ring via phenoxymethyl spacers was reported. First attempt to synthesize 4, 5, 6 by the reaction of the appropriate bis(acetophenones) with 4‐amino‐3‐mercapto‐1,2,4‐triazole derivatives using an acidified acetic acid method were unsuccessful. On the other hand, reaction of the corresponding bis(α‐bromoketones) with 4‐amino‐3‐mercapto‐1,2,4‐triazole derivatives afforded 4, 5, 6 in good yields. The reaction pathway is assumed to involve S‐alkylation to give bis(aminotriazole) intermediates, followed by intramolecular cyclocondensation to give 4, 5, 6. The successful isolation of the corresponding bis(aminotriazole) intermediates provides strong evidence for the proposed mechanism. The novel bis(thiazoles) 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, linked to alkyl or aryl spacers can also be synthesized by reaction of the appropriate bis(bromoacetyl) compounds 12a, 12b, 12c and 14, 15, 16, 17, 18, 19 with the corresponding thioamide derivatives 20, 21, 22.