Synthesis
General procedure for the synthesis of 1-methyl-3-trifluoromethyl-1H-pyrazole-4-carboxylic acid from ethyl 1-methyl-3-trifluoromethyl-1H-pyrazole-4-carboxylate: to a reaction vial, ethyl 1-methyl-3-(trifluoromethyl)-1H-pyrazole-4-carboxylate (5600 mg, 25 mmol) and potassium hydroxide (4740 mg, 30 mmol) were added in 50 mL of solvent. The reaction mixture was stirred at room temperature overnight. Upon completion of the reaction, the reaction solution was acidified to pH 1 with dilute hydrochloric acid and a white solid product was precipitated. The solid was collected by filtration and washed with an appropriate solvent and dried to give 1-methyl-3-trifluoromethyl-1H-pyrazole-4-carboxylic acid in 59% yield with a melting point of 195-196 °C. The structure of the product was confirmed by 1H NMR (500 MHz, DMSO-d6) with chemical shifts of δ 12.80 (s, 1H, COOH), 8.44 (s, 1H, CH on the pyrazole ring), 3.93 (s, 3H, CH3).
References
[1] Angewandte Chemie - International Edition, 2017, vol. 56, # 16, p. 4569 - 4574
[2] Angew. Chem., 2017, vol. 129, # 16, p. 4640 - 4645,6
[3] Molecules, 2012, vol. 17, # 12, p. 14205 - 14218
[4] Journal of Molecular Structure, 2018, vol. 1171, p. 631 - 638
[5] Patent: EP2263999, 2010, A1. Location in patent: Page/Page column 21-22
