Acetohydrazide → 3-methyl-5-phenyl-1H-1,2,4-triazole

To a suspension of ethyl benzimidate hydrochloride (2.0 g, 10.8 mmol) in EtOH (10 mL) was added sodium ethoxide (3.49 g, 4 mL, 10.8 mmol) at RT. The precipitated NaCl was filtrated off and washed with EtOH (14 mL). The filtrate was charged with acetohydrazide (880 mg, 11.9 mmol) and stirred at RT for 6 d. The crude reaction mixture was concentrated in vacuo. The crude product was suspended in NaOH (1M aqueous solution, 50 mL) and extracted with tert-butyl methyl ether (100 mL). The organic layer was washed with water (50 mL) and the aqueous layers were back-extracted with tert-butyl methyl ether (50 mL). After addition of dry ice to adjust the pH to 7, the organic layer appeared to contain almost no product and was discarded. The aqueous layer was adjusted to pH=7 by addition of HCl (25% aqueous solution) and extracted with dichloromethane (6×50 mL). The combined organic layer was dried over MgSO4 and concentrated in vacuo. The product was obtained after purification by flash chromatography (using silica gel and an ethyl acetate/hexane gradient) as white solid (154 mg, 9%).