反应详情

Solution of 5-isopropyl-2-phenyl-oxazole-4-carboxylic acid benzyl ester (830 mg, 2.59 mmol) in a mix of tetrahydrofuran, methanol and water (3:1:1, 10 mL) was treated with lithium hydroxide monohydride (258 mg, 6.5 mmol) at room temperature for an hour. After the reaction was complete, solvent was removed. To the residue, water and dichloromethane were added, and white precipitate formed. After filtering off the solid, filtrate was collected and the phases were separated. The pH of the aqueous layer was adjusted to 1˜2 with dilute hydrochloride acid (1N). Then the aqueous layer was extracted with ethyl acetate three times. The ethyl acetate layers were collected, dried over sodium sulfate, and concentrated in vacuo. Flash chromatography (Merck silica gel 60, 230-400 mesh, 0-80% ethyl acetate in hexane for 20 min) gave 5-isopropyl-2-phenyl-oxazole-4-carboxylic acid (247 mg, 41%) as a white solid. LCMS calcd for C13H13NO3 (m/e) 231, obsd 232 (M+H).

1. customsolvent was removed
2. additionTo the residue, water and dichloromethane were added
3. customwhite precipitate formed
4. filtrationAfter filtering off the solid, filtrate
5. customwas collected
6. customthe phases were separated
7. extractionThen the aqueous layer was extracted with ethyl acetate three times
8. customThe ethyl acetate layers were collected
9. dry with materialdried over sodium sulfate
10. concentrationconcentrated in vacuo