5-Acetyl-1H-pyrazole-3-carboxylic acid is a chemical compound that is synthesized from hydrazine and acetyl chloride.
Potassium tert-butoxide (102 g) was added lot-wise to the pre-cooled mixture of 3,3-dimethoxybutane-2-one (100 g) in toluene (1000 ml) at 5-10°C and stirred for 45 minutes. Diethyl oxalate (132 g) was added to the mixture at 10-15°C and stirred for 4 hours. Filtered the solid. To the filtered solid water (3000 ml) was added and cooled to 5-10°C. Solution of Hydrazine monohydrochloride (51.8 g) was slowly added to the mixture at 5-10°C and stirred for 4 hrs. Dichloromethane (1000 ml) was added to the mixture at 5-10°C and stirred for 15 minutes. Allowed to heat the mixture to 25-30°C and stirred for 15 minutes. Filtered the mixture through hyflow. Organic layer was separated from the filtrate. Distilled-off the organic layer and co-distilled in n-heptane (50 ml). n-heptane (300 ml) was added to the mixture at 25-30°C. Heated the mixture at 45-50°C and stirred for 1 hrs. Allowed to cool the mixture to 25-30°C and stirred for 3 hours. Filtered the solid. THF (150 ml) was added to the obtained solid. aq. Sodium hydroxide solution was added to the mixture at 10-15°C. Heated the mixture to 55-60°C and stirred for 2 hrs. Allowed to cool the mixture to 25-30°C and stirred for 15 minutes. Separated the aqueous layer from organic layer. Water was added to the aqueous layer at 25-30°C. Cooled the mixture to 20-25°C. Treated the mixture with hydrochloric acid at 20-25°C. Allowed to heat the mixture to 25-30°C and stirred for 4 hours. Filtered the solid and dried. Tetrahydrofuran (300 ml) was added to the obtained solid at 25-30°C. Heated the mixture to 50-55°C and stirred for 60 minutes. Allowed to cool the mixture to 25-30°C and stirred for 3 hours. Filtered the solid and dried to get 5-Acetyl-1H-pyrazole-3-carboxylic acid, Yield: 63 gm Purity by HPLC: 99.93%.
