反应详情

33 g. of 5-amino-1-ethylpyrazole (0.3 mol.) in 310 g. of polyphosphoric acid are heated to 80° (bath temperature). While stirring, 70.5 g. of 2-(2-phenylethyl)acetoacetic acid, ethyl ester (0.3 mol.) are added to the mixture. The bath temperature is increased to 100°, the temperature of the solution rising to about 130°. As soon as the reaction temperature begins to drop the bath temperature is elevated to 140° and maintained for 45 minutes. After the mixture has cooled to room temperature, 650 ml. of water are added in portions and stirring is continued until the polyphosphoric acid is dissolved. The the aqueous phosphoric acid solution is decanted and the undissolved residue is treated with 400 ml. of 5% aqueous ammonia to neutralize the mixture. The mixture is extracted with chloroform and the chloroform extract is washed with water and dried with Na2SO4. Addition of ether precipitates 37 g. (44%) of 1-ethyl-6-methyl-5-(2-phenylethyl)-1H-pyrazolo[3,4-b]pyridin-4-ol; m.p. 251°-256°. Recrystallization from ethanol raises the m.p. to 258°-260°.

1. temperatureThe bath temperature is increased to 100°
2. customrising to about 130°
3. customis elevated to 140°
4. temperaturemaintained for 45 minutes
5. stirringstirring
6. dissolutionis dissolved
7. customThe the aqueous phosphoric acid solution is decanted
8. additionthe undissolved residue is treated with 400 ml
9. extractionThe mixture is extracted with chloroform
10. extractionthe chloroform extract
11. washis washed with water
12. dry with materialdried with Na2SO4
13. additionAddition of ether
14. customprecipitates 37 g
15. customRecrystallization from ethanol
16. temperatureraises the m.p. to 258°-260°