Hydrazine, dihydrochloride → 3-(Trifluoromethyl)pyrazole

Hydrazine dihydrochloride (225 g, 2.14 mol) in ethanol (1400 mL) was stirred well. TEA (185.4 mL, 1.34 mol) was added drop wise for 45 min at ambient temperature. Then (E)-4-ethoxy-1,1,1-trifluorobut-3-en-2-one (225 g, crude) was added drop wise at room temperature and the overall reaction mixture was refluxed overnight. Progress of the reaction was monitored by TLC (20% ethyl acetate/hexane, Rf˜0.4). On completion of the reaction, ethanol was distilled off completely, residue was taken in ice water (500 mL) and the product extracted with ethyl acetate (2×400 mL). Combined extract was washed with ice water (300 mL), dried over sodium sulfate and concentrated under reduced pressure to yield 3-(trifluoromethyl)-1H-pyrazole as a off white solid (175 g, crude).