反应详情

151 g of the above product from (a) are stirred with 650 ml of 2N sodium hydroxide solution at 90° C. until a clear solution has formed. The solution is cooled and then washed with 200 ml of methylene chloride, the aqueous phase is acidified with concentrated hydrochloric acid and extracted several times with methylene chloride, and the extract is dried and evaporated down to give a colorless residue which crystallizes spontaneously. Yield: 129 g (88% of theory, based on methyl 1-hydroxypyrazole-4-carboxylate). M.p.: 85° C.

1. customhas formed
2. temperatureThe solution is cooled
3. washwashed with 200 ml of methylene chloride
4. extractionextracted several times with methylene chloride
5. customthe extract is dried
6. customevaporated down
7. customto give a colorless residue which
8. customcrystallizes spontaneously