反应详情

Concentrated sulfuric acid. (10 drops) was added to a stirred methanol suspension of thoroughly dried 19 (0.60 g, 2.0 mmol) under argon and heated at reflux for 18 h. Methanol was evaporated under reduced pressure, residue was taken up in ethyl acetate (20 mL) and washed with water (20 mL), saturated aqueous Na HCO3 (10 mL) and brine (10 mL). The organic layer was dried on anhydrous magnesium sulfate, filtered and the solvent was evaporated. The crude product obtained was purified by chromatography over silica gel and eluted with hexane-ethyl acetate (7:3) to yield 20 as white solid (0.24 g, 35%): 1HNMR (400 MHz, CDCl3) δ 7.26 (d, J=8.4 Hz, 2H), 6.82 (s, 1H), 6.76 (d, J=8.4 Hz, 2H), 6.45 (d, J=2.0 Hz, 2H), 6.34 (t, J=2.0 Hz, 1H), 4.97 (s, 1H), 3.73 (s, 3H), 3.72 (s, 6H).

1. temperatureheated
2. temperatureat reflux for 18 h
3. customMethanol was evaporated under reduced pressure, residue
4. washwashed with water (20 mL), saturated aqueous Na HCO3 (10 mL) and brine (10 mL)
5. dry with materialThe organic layer was dried on anhydrous magnesium sulfate
6. filtrationfiltered
7. customthe solvent was evaporated
8. customThe crude product obtained
9. customwas purified by chromatography over silica gel
10. washeluted with hexane-ethyl acetate (7:3)