反应详情

39 g. of 2-methyl-6-phenyl-2H-pyrazolo[3,4-b]pyridin-4-ol (0.17 mol.) are refluxed in 195 ml. of phosphorus oxychloride for 90 minutes. The excess phosphorus oxychloride is removed in vacuo and the residue is poured onto ice. Concentrated aqueous ammonia is added under external cooling to adjust the mixture to pH 8-9. Stirring is continued for one additional hour. The collected 4-chloro-2-methyl-6-phenyl-2H-pyrazolo[3,4-b]pyridine is washed with water and dried at 70°, yield: 41 g. (100%); m.p. 177°-179°. Recrystallization from ethyl acetate gives a melting point of 189°-190°.

1. customThe excess phosphorus oxychloride is removed in vacuo
2. additionthe residue is poured onto ice
3. additionConcentrated aqueous ammonia is added
4. temperatureunder external cooling
5. washThe collected 4-chloro-2-methyl-6-phenyl-2H-pyrazolo[3,4-b]pyridine is washed with water
6. customdried at 70°
7. customRecrystallization from ethyl acetate
8. customgives a melting point of 189°-190°