16034-46-1

930-36-9

124-38-9

16034-46-1

1-Methyl-1H-pyrazole (2.0 g, 24.4 mmol) was dissolved in tetrahydrofuran (THF, 30 mL) at room temperature. The reaction mixture was cooled to -78 °C under nitrogen protection, followed by slow dropwise addition of n-butyllithium (n-BuLi, 10.72 mL, 26.8 mmol). The reaction temperature of -78 °C was maintained and the reaction mixture was stirred for 2 h. Subsequently, it was gradually warmed up to room temperature and stirring was continued for 1 h. The reaction temperature was maintained at -78 °C. Under the condition of maintaining the reaction temperature, dry carbon dioxide gas was passed into the reaction solution for about 5 minutes. The reaction mixture continued to be stirred at room temperature for 1 hour. Subsequently, water (30 mL) was added to the reaction mixture to quench the reaction and dilute the mixture. The reaction mixture was extracted with dichloromethane. After precipitation of a large amount of solid from the acidic aqueous phase, the separation was carried out by filtration. The resulting filter cake was dried to give a final 1.5 g of white solid product 1-methyl-1H-pyrazole-5-carboxylic acid in 48.8% yield.