Urea → Ethyl 4-hydroxyisoxazole-3-carboxylate

Temperature

100 °C

144 g of urea were added to 1 liter of a dimethylformamide solution containing 72 g of ethyl 4-bromo-2-hydroxyimino-3-oxobutyrate. The reaction solution was heated for 15 minutes at 100° C. and then cooled, after which water was added to the reaction solution, and the mixture was extracted with ethyl acetate. The extract was washed with dilute aqueous hydrochloric acid and with a saturated aqueous solution of sodium chloride, in that order, after which it was dried over anhydrous sodium sulfate. The solvent was then removed by distillation under reduced pressure, and a 1:1 by volume mixture of ethyl acetate and hexane was added to the residue, to remove insoluble materials. The solution thus obtained was purified by silica gel chromatography, eluted with a 1:4 by volume mixture of ethyl acetate and hexane, to give 19 g of the title compound, melting at 59°-60° C. (after recrystallization from a mixture of ethyl acetate and hexane).

1. temperaturecooled
2. extractionthe mixture was extracted with ethyl acetate
3. washThe extract was washed with dilute aqueous hydrochloric acid and with a saturated aqueous solution of sodium chloride, in that order
4. dry with materialafter which it was dried over anhydrous sodium sulfate
5. customThe solvent was then removed by distillation under reduced pressure
6. additiona 1:1 by volume mixture of ethyl acetate and hexane
7. additionwas added to the residue
8. customto remove insoluble materials
9. customThe solution thus obtained
10. customwas purified by silica gel chromatography
11. washeluted with a 1:4 by volume mixture of ethyl acetate and hexane

ORD record

ord-df8ceb63540f48a3bd61c4d66f026a5f

Source dataset

uspto-grants-1997_04

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US05616579