2-Methyl-5-trifluoromethyl-2H-pyrazole-3-carboxylic acid

1236144-18-5

128694-63-3

General procedure for the synthesis of 1-methyl-3-(trifluoromethyl)-1H-pyrazole-5-carboxylic acid from ethyl 1-methyl-3-(trifluoromethyl)-1H-pyrazole-5-carboxylate: To a 15 mL Schlenk reaction flask containing ethyl 1-methyl-3-(trifluoromethyl)-1H-pyrazole-5-carboxylate (1.5 mmol) was added a solution of 1 N sodium hydroxide (2.5 mL), the The resulting mixture was stirred vigorously for 24 h at room temperature. Upon completion of the reaction, the reaction mixture was acidified with 6 N HCl at 0 °C. The resulting solid was collected by filtration and the solid was suspended in dichloromethane. The organic and aqueous layers were separated and the aqueous layer was further extracted with dichloromethane. All organic layers were combined and dried with anhydrous Na2SO4 and subsequently concentrated under reduced pressure to remove the solvent. The residue was purified by silica gel column chromatography (eluent ratio: hexane/EtOAc = 5:1 to 2:1) to afford 1-methyl-3-trifluoromethyl-5-pyrazolecarboxylic acid (275 mg, 95% yield) as a white solid.