General procedure for the synthesis of 3-trifluoromethyl-4-(hydroxymethyl)pyrazole from ethyl 3-trifluoromethylpyrazole-4-carboxylate: ethyl 3-(trifluoromethyl)-1H-pyrazole-4-carboxylate (95.00 g, 0.456 mol) was dissolved in anhydrous tetrahydrofuran (THF, 1 L) and the resulting solution was cooled in an acetone/ice bath. A 1 M solution of lithium tetrahydroaluminum (LiAlH4) in THF (550 mL, 0.550 mol) was slowly added over a period of 30 min, keeping the reaction temperature below 10 °C. Subsequently, the cooling device was removed and the reaction mixture was stirred at room temperature for 4 hours. The reaction was cooled again and a 1:1 solution of THF:water mixture (250 mL) was slowly added under cooling conditions, keeping the temperature below 20 °C, followed by the addition of 5 M hydrochloric acid (HCl, 160 mL) adjusted to neutral (pH 6). Ethyl acetate (EtOAc, 1.5 L) was added and the mixture was stirred for 30 min and then left overnight. The resulting gray granular solid was removed by diatomaceous earth filtration and washed with ethyl acetate. The combined filtrates were washed with brine, dried over anhydrous magnesium sulfate (MgSO4) and subsequently concentrated under vacuum to give a white solid product (76.00 g, 0.457 mol, 100% yield).1H NMR (400 MHz, CD3OD) data: δ 4.61 (s, 2H), 7.75 (s, 1H).
