1-Methyl-1H-pyrazol-3(2H)-one

5788-17-0

52867-35-3

Example 7: General procedure for the synthesis of 1-methyl-1H-pyrazol-3(2H)-one from methyl 3-methoxyacrylate and monomethylhydrazine. In a 250 mL flask, 70 g of methanol and 60.5 g (0.46 mol) of 35% concentration of monomethylhydrazine aqueous solution were first added and the reaction temperature was kept at 25 °C. Subsequently, 47.8 g (0.40 mol) of methyl 3-methoxyacrylate was slowly added dropwise over 25 min. The pH of the reaction mixture was maintained at 12 by parallel dropwise addition of a 17% concentration of aqueous NaOH solution during the dropwise addition and during subsequent stirring for 6 h. A total of 97.5 g of NaOH solution was consumed for this process. The yield of the target product 1-methyl-1H-pyrazol-3(2H)-one was 75% when the reaction reached 100% conversion. The ratio of 3-hydroxy isomer to 5-hydroxy isomer in the product was ≥15:1.