2,5-Dihydro-1,2,3,5-thiatriazole1-oxides, 2H-1,2,3,5-thiatriazol-1-ium salts, and 2,5-dihydro-1,2,3,5-thiatriazol-5-yl radicals. X-Ray molecular structure of 2,5-dihydro-2,4-diphenyl-1,2,3,5-thiatriazole 1-oxide and 2,4-diphenyl-2H-1,2,3,5-thiatriazol-1-ium bromide

Abstract

N-Substituted amidrazones (4a–g) react with thionyl chloride to give 2,5-dihydro-1,2,3,5-thiatriazole 1-oxides (5a–g). X-Ray analysis of compound (5c) confirmed the 2,5-dihydro structure which is also the predominant tautomer in solution. Reaction of compounds (5a–g) with phosphorus pentachloride or pentabromide led to the formation of yellow 2H-1,2,3,5-thiatriazol-1-ium salts (6a–h), the structure being established by X-ray structure analysis of compound (6h). Reduction of compounds (6a–h) in 1,2-dimethoxyethane with sodium or potassium metal readily generated 2,5-dihydro-1,2,3,5-thiatriazol-5-yl radicals (1a–g) which were studied using ESR, EN DOR, and general triple resonance spectroscopy. The results led to a complete analysis and full assignment of all coupling constants.