反应详情

47 g of 1-ethyl-4-hydroxy-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester (0.2 mol) are saponified by means of 400 ml of aqueous sodium hydroxide (2.5 N) by refluxing the mixture for 1 1/2 hours. After cooling of the filtering solution and diluting with 300 ml of water, it is acidified with glacial acetic acid. The precipitated 1-ehyl-4-hydroxy-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid is filtered under suction, washed with water and dried at 120°. Yield 37 g (89%), recrystallization from glacial acetic acid, and has a melting point of 201°-292°.

1. temperatureby refluxing the mixture for 1 1/2 hours
2. temperatureAfter cooling of the filtering solution
3. filtrationThe precipitated 1-ehyl-4-hydroxy-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid is filtered under suction
4. washwashed with water
5. customdried at 120°
6. customYield 37 g (89%), recrystallization from glacial acetic acid