Synthesis
General procedure for the synthesis of 3-ethyl-1-methyl-1H-pyrazole-5-carboxylic acid from ethyl 3-ethyl-1-methyl-1H-pyrazole-5-carboxylate: ethyl 3-ethyl-1-methyl-1H-pyrazole-5-carboxylate (50 mmol), sodium hydroxide (150 mmol), water (120 mL), and ethanol (20 mL) were mixed, and the reaction was stirred under reflux conditions for 4-5 hours. After completion of the reaction, the reaction solution was cooled to room temperature and separated by extraction with ethyl acetate. The aqueous phase was collected and the pH was adjusted to 5-6 with dilute hydrochloric acid, acidified and left to precipitate the product. The precipitate was collected by filtration and dried to give 3-ethyl-1-methyl-1H-pyrazole-5-carboxylic acid in 4.8 g yield.
References
[1] Journal of Agricultural and Food Chemistry, 2012, vol. 60, # 6, p. 1470 - 1479
[2] Patent: CN106608873, 2017, A. Location in patent: Paragraph 0111; 0112; 0115
[3] Patent: CN106608872, 2017, A. Location in patent: Paragraph 0104; 0107
[4] Chemical Papers, 2017, vol. 71, # 11, p. 2053 - 2061
[5] European Journal of Medicinal Chemistry, 2018, vol. 149, p. 170 - 181
