反应详情

253 g of [[(1-ethyl-5-pyrazolyl)amino]methylene]malonic acid diethyl ester (0.09 mol) is dissolved in 770 g of diphenyl ether. The reaction mixture is heated to 235°-250° (bath temperature) and allowed to react at this temperature for 1 to 2 hours, while the resulting ethanol is continuously distilled off. The remaining alcohol is removed by means of a water aspirator. The diphenyl ether is separated by distillation with a fractionating column in vacuo. The 1-ethyl-4-hydroxy-1H-pyrazolo[3,4-b]pyridinecarboxylic acid ethyl ester is obtained at b.p. 0.05 115°-120°, yield 195 g = 92% of theory, m.p. 85°-87°. The compound is recrystallized from ligroin (90° to 100°), and has a melting point of 87°-89°.

1. temperatureThe reaction mixture is heated to 235°-250° (bath temperature)
2. distillationis continuously distilled off
3. customThe remaining alcohol is removed by means of a water aspirator
4. customThe diphenyl ether is separated by distillation with a fractionating column in vacuo