反应详情

温度

60 °C

Phosphorus oxychloride (5.07 ml) was added dropwise to dimethylformamide (8.4 ml) at 0° C. under nitrogen. Ethyl pyruvate semicarbazide (4.3 g, Reference Example 58) was added portionwise to the stirring solution at 0° C. under a nitrogen positive pressure. The reaction mixture was heated at 60° C. for 2.5 hours and cooled to ambient temperature before pouring slowly onto ice (30 g). The pH of the reaction mixture was adjusted to pH12 with 6.25M sodium hydroxide solution whilst maintaining the temperature at 0° C. The aqueous reaction mixture was heated at 60° C. for 5 minutes and cooled to 0° C. The pH was re-adjusted to pH6 with 1M hydrochloric acid. The resulting precipitate which formed after 1 hour was collected by filtration to yield 4-formyl-1H-pyrazole-3-carboxylic acid ethyl ester (1.02 g) as a pale yellow solid. LC-MS (Method J): RT=2.55 minutes, 169.27 (M+H)+, 167.30 (M−H)−

1. temperaturecooled to ambient temperature
2. additionbefore pouring slowly onto ice (30 g)
3. temperaturewhilst maintaining the temperature at 0° C
4. temperatureThe aqueous reaction mixture was heated at 60° C. for 5 minutes
5. temperaturecooled to 0° C
6. customThe resulting precipitate which formed after 1 hour
7. filtrationwas collected by filtration