反应详情

Concentrated HCl (450 ml) was added to ethyl 2,4-dioxovalerate ( 177.8 g, 1.1 mol ) followed by hydroxylamine hydrochloride (103.7 g, 1.68 mol). The reaction mixture was stirred for 7 hours, then allowed to stand for 60 hours. The solvent was removed in vacuo and the residue was chilled on ice. A solid formed which was collected by filtration and washed with cold water. The solid was dissolved in THF (11), the solution was filtered and the solvent was removed in vacuo. The residue was slurried with ethyl acetate (200 ml) and the solid collected by filtration. Concentration of filtrate to approximately 30 ml afforded a second crop of the product. The two crops were combined and recrystallized from methanol to afford 82.1 g (58%) of 3-methylisoxazole-5-carboxylic acid, m.p. 209°-211° C.

1. waitto stand for 60 hours
2. customThe solvent was removed in vacuo
3. temperaturethe residue was chilled on ice
4. customA solid formed which
5. filtrationwas collected by filtration
6. washwashed with cold water
7. dissolutionThe solid was dissolved in THF (11)
8. filtrationthe solution was filtered
9. customthe solvent was removed in vacuo
10. filtrationthe solid collected by filtration
11. customConcentration of filtrate to approximately 30 ml afforded a second crop of the product
12. customrecrystallized from methanol