反应详情

To 80.3 g. of 4-chloro-1-ethyl-3-methyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid, ethyl ester (0.3 mol.) [prepared according to Journal of Heterocyclic Chemistry 9, 235-253 (1972)] dissolved in 270 ml. glacial acetic acid, are added 33.4 g. of triethylamine (0.33 mol.) and 7.5 g. of palladium on charcoal (10%). The mixture is hydrogenated at room temperature and a pressure of 2.5 atm. After about 19 hours the theoretical amount of hydrogen is absorbed. Then the catalyst is filtered off and the filtrate evaporated. The residue is treated with 200 ml. of water and extracted with ether. The combined ether extracts are dried and the ether distilled off. The oily 1-ethyl-3-methyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid, ethyl ester is distilled in vacuo; b.p.0.3 144°-146°, which after a short time begins to crystallize, yield: 64.5 g. (92%).

1. customis hydrogenated at room temperature
2. customAfter about 19 hours the theoretical amount of hydrogen is absorbed
3. filtrationThen the catalyst is filtered off
4. customthe filtrate evaporated
5. additionThe residue is treated with 200 ml
6. extractionof water and extracted with ether
7. dry with materialThe combined ether extracts are dried
8. distillationthe ether distilled off
9. distillationThe oily 1-ethyl-3-methyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid, ethyl ester is distilled in vacuo
10. customb.p.0.3 144°-146°, which
11. customto crystallize