Diphenyl Ether → HCID 178469631, compound

Participants

Reaction Steps

253 g. [[(1-Ethyl-5-pyrazolyl)amino]methylene]malonic acid diethyl ester (0.09 mol.) are 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 1-2 hours while the resulting ethanol is continuously distilled off. The last amount of 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]pyridine-5-carboxylic acid ethyl ester is obtained at b.p. 0.05 115°-120°, yield 195 g. (92%), m.p. 85°-87°. The compound is recrystallized from ligroin (90°-100°), m.p. 87°-89°. Hydrolysis of this product with aqueous sodium hydroxide yields 1-ethyl-4-hydroxy-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid, m.p. 201°-202°.

Provenance & Evidence