5744-56-9

10250-59-6

5744-56-9

1. 1,3-Dimethyl-1H-pyrazole-5-carboxylic acid methyl ester (5.14 kg) was slowly added to 20% aqueous sodium hydroxide solution (10 L) at 0 °C. 2. The reaction mixture was stirred at room temperature for 18 hours and then cooled to 0 °C. 3. Concentrated hydrochloric acid (4.2 L) was added slowly to the reaction mixture over a period of 7 hours. 4. The thick slurry formed was stirred for 18 hours at room temperature. 5. Stirring was continued at room temperature for 18 h. 5. The reaction mixture was filtered and the solid product was washed with water (500 mL). 6. The solid product was dried in a vacuum oven at 70 °C and 26 mmHg for 18 h to give 1,3-dimethyl-1H-pyrazole-5-carboxylic acid (3.8 kg, 81% yield, HPLC purity >97%).