General procedure for the synthesis of 5-phenyl-1,3,4-oxadiazole-2-thione from carbon disulfide and benzoylhydrazine: a mixture of benzoylhydrazine (0.41 g, 3 mmol), potassium phosphate (1.02 g, 3 mmol) and carbon disulfide (0.23 g, 3 mmol) in water (15 mL) was stirred at room temperature for 10 minutes. The reaction mixture was then heated to reflux for 2 hours. After completion of the reaction, the pH was adjusted to 7 with 1N HCl, the precipitated solid was filtered and dried in vacuum to afford 5-phenyl-1,3,4-oxadiazole-2-thione (0.51 g, 96%) as a white solid. Melting point: 197-199°C (literature value: 199-201°C).1H NMR (400MHz, CDCl3) δ10.52 (broad single peak, 1H), 7.93 (double peak, J=7.2Hz, 2H), 7.42-7.65 (multiple peaks, 3H).
