Synthesis of 3,6-bisubstituted phenyl-bi-1,2,4-triazolo[3,4-b]1,3,4-thiadiazole derivatives

2,5-Bihydrazino-1,3,4-thiadiazole was synthesized by substitution of 2,5-bimercapto-1,3,4-thiadiazole with hydrazine hydrate and reacted with benzoyl chloride to give 2,5-biacylhydrazino-1,3,4-thiadiazole, which was further ring-closed by POCl3 as cyclization agent to synthesize 3,6-bisubstituted phenyl-bi-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazole derivatives. The novel compounds were confirmed by elemental analysis, IR, H-1 NMR and MS spectra. The mechanism of cycloreaction was also discussed.