反应详情

1-Methyl-1H-pyrazole-3,5-dicarboxylic acid dimethyl ester (640, 3.7 g, 19.0 mmol) was combined with 1,4-dioxane (20 mL) and water (60 mL). Concentrated sulfuric acid (1.0 mL) in 2 mL of water was added to the solution. After the reaction was stirred at reflux overnight, it was cooled to room temperature and concentrated until precipitation began. The obtained mixture was left standing overnight. The resulting solid was filtered and dried under reduced pressure. The collected aqueous fractions were extracted with ethyl acetate. The organic portion was dried over anhydrous sodium sulfate and concentrated. Additional solid was crystallized from ethyl acetate to give the desired compound (641, 2.33 g, 68%). MS (ESI) [M+H+]+=185.0, melting point 175° C.

1. temperatureat reflux overnight
2. concentrationconcentrated until precipitation
3. waitThe obtained mixture was left
4. filtrationThe resulting solid was filtered
5. customdried under reduced pressure
6. extractionThe collected aqueous fractions were extracted with ethyl acetate
7. dry with materialThe organic portion was dried over anhydrous sodium sulfate
8. concentrationconcentrated
9. customAdditional solid was crystallized from ethyl acetate