17827-60-0

Under argon protection, 1-methyl-1H-pyrazole-5-carboxylic acid (5 g, 39.7 mmol) was dissolved in methanol (100 mL) and cooled to 0 °C. Thionyl chloride (103.2 mmol) was slowly added dropwise, keeping the reaction temperature at 0 °C. After the dropwise addition, the reaction mixture was gradually warmed up to room temperature and stirred continuously for 12 hours. After completion of the reaction, the reaction mixture was concentrated under reduced pressure. The concentrate was diluted with water (100 mL) and centrifuged with saturated aqueous sodium bicarbonate solution to pH neutral. Subsequently, extraction was performed with ethyl acetate (100 mL x 3). The organic phases were combined and dried over anhydrous sodium sulfate. The desiccant was removed by filtration and the filtrate was concentrated under reduced pressure to give methyl 1-methyl-1H-pyrazole-5-carboxylate as a white solid in 90% yield (5 g) with a mass m/z of 240, which did not require further purification.

[1] Patent: WO2014/151142, 2014, A1. Location in patent: Paragraph 0092
[2] Bulletin of the Academy of Sciences of the USSR, Division of Chemical Science (English Translation), 1980, vol. 29, # 5, p. 778 - 784
[3] Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, 1980, # 5, p. 1071 - 1077