反应详情

Ethyl 3,4-dihydroxybenzoate (910.9 mg, 5 mmol) was combined with 2,2-dimethoxypropane (1.23 mL, 10 mmol) and a catalytic amount of p-toluene sulfonic acid in toluene. The mixture was heated to reflux using a Dean-Stark trap for 20 hours. After solvent removal under reduced pressure, the crude was dissolved in ethyl acetate and washed successively with a saturated aqueous solution of sodium bicarbonate, water, and brine. The organic layer was dried over anhydrous sodium sulfate. Purification by chromatography on silica gel using a gradient hexane:ethyl acetate, 90:10 to 75:25, afforded a white powder (539.1 mg, 49%). 1H NMR (CDCl3): 1.36 (t, 3H, J=7.2 Hz), 1.69 (s, 6H), 4.32 (q, 2H, J=7.1 Hz, J=14.2 Hz), 6.74 (d, 1H, d, J=8.2 Hz), 7.38 (d, 1 h, J=1.7 Hz), 7.61 (dd, 1H, J=1.8 Hz, J=8.3 Hz).

1. temperatureThe mixture was heated
2. temperatureto reflux
3. customfor 20 hours
4. customAfter solvent removal under reduced pressure
5. dissolutionthe crude was dissolved in ethyl acetate
6. washwashed successively with a saturated aqueous solution of sodium bicarbonate, water, and brine
7. dry with materialThe organic layer was dried over anhydrous sodium sulfate
8. customPurification by chromatography on silica gel using a gradient hexane