反应详情

A mixture of 2-hydroxy-5-nitrobenzoic acid (50.0 g, 0.27 mol), acetone (40 mL, 0.54 mol) and trifluoroacetic anhydride (100 mL, 0.71 mol) in TFA (300 mL) was heated at reflux. After 1 hour, a supplementary amount of acetone (60 mL, 0.82 mol) was added and the reaction mixture was refluxed for 48 hours. The solvents were evaporated under reduced pressure. The residual brown solid was dissolved in DCM (800 mL) and washed with a mixture of saturated aqueous NaHCO3 (400 mL) and water (400 mL). The aqueous layer was extracted with DCM (2×400 mL). The combined organic layers were dried over MgSO4 and the solvent was removed under reduced pressure. The residual brown oil was taken up in cold pentane (300 mL, 0° C.) and a yellow solid precipitated off. Filtration and washing with pentane gave 53.8 g (88%) of the title compound as a yellow solid. HPLC, Rt: 2.9 min (purity: 99.8%). 1H NMR (CDCl3) δ: 8.88 (d, J=2.8 Hz, 1H), 8.44 (dd, J=9.0, 2.8 Hz, 1H), 7.14 (d, J=9.0 Hz 1H), 1.80 (s, 6H).

1. temperaturewas heated
2. temperatureat reflux
3. temperaturethe reaction mixture was refluxed for 48 hours
4. customThe solvents were evaporated under reduced pressure
5. dissolutionThe residual brown solid was dissolved in DCM (800 mL)
6. washwashed with a mixture of saturated aqueous NaHCO3 (400 mL) and water (400 mL)
7. extractionThe aqueous layer was extracted with DCM (2×400 mL)
8. dry with materialThe combined organic layers were dried over MgSO4
9. customthe solvent was removed under reduced pressure
10. customwas taken up in cold pentane (300 mL, 0° C.)
11. customa yellow solid precipitated off
12. filtrationFiltration
13. washwashing with pentane