Synthesis of 1,2,4-Triazole-3-Thiol Derivatives from Thiosemicarbazides and Carboxylic Acids Using Polyphosphate Ester.

Conditions have been established for the direct reaction of thiosemicarbazides with carboxylic acids in the presence of polyphosphate ester (PPE) to synthesize 1,2,4-triazole-3-thiol derivatives. The synthesis involves two consecutive steps: (i) acylation of the thiosemicarbazide with a carboxylic acid in chloroform in the presence of PPE at 90 °C using a hydrothermal reaction vessel, followed by (ii) cyclodehydration of the acylation product by treatment with an aqueous alkali solution. Using this new synthetic approach, 15 derivatives of 1,2,4-triazole-3-thiol were obtained, five of which were synthesized for the first time. The structures of the synthesized compounds were confirmed by NMR spectroscopy and mass spectrometry.