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

Abstract

2,5-Bihydrazino-1,3,4-thiadiazole (2) was synthesized by condensation of 2,5-bimercapto-1,3,4-thiadiazole (1) with hydrazine hydrate, and compound 2 reacted with acyl chloride to give 2,5-biacylhydrazino-1,3,4-thiadiazole derivatives (3a?3e). Ring closure of compounds 3a?3e was achieved with POCl₃ as the cyclization agent giving 3,6-bisubstituted phenyl-bi-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazole derivatives (4a?4e), respectively. The novel compounds were identified by elemental analysis, and by infrared (IR), ¹H- nuclear magnetic resonance (NMR), and mass (MS) spectrometry. The mechanism of the cyclization is also discussed.