反应详情

To a mixture of methyl 4-bromo-3,5-dihydroxybenzoate (18.8 g, 76 mmol) and potassium carbonate (5.26 g, 38.1 mmol) in DMF (190 mL) was added benzyl bromide (3.17 mL, 26.6 mmol). The mixture was stirred overnight, diluted with 200 mL water and acidified to pH 1 by slow addition of concentrated hydrochloric acid. The solution was extracted with 1:1 ethyl acetate/ether (6×) and the combined extracts were washed with water (8×), saturated sodium bicarbonate, brine, then dried over magnesium sulfate and concentrated to provide an orange solid. The solid was suspended in DCM (200 mL) and stirred overnight. The solid (primarily unreacted 4-bromo-3,5-dihydroxybenzoate) was removed by filtration and the filtrate was concentrated to provide an orange oil which was purified by column chromatography (80 g silica gel, 2:1 DCM in heptane elution, followed by DCM elution) to provide methyl 3-(benzyloxy)-4-bromo-5-hydroxybenzoate (4.66 g). MS (M+1)=337.0. 1H NMR (400 MHz, CHLOROFORM-d) δ ppm 7.32-7.57 (m, 6H), 7.26 (d, J=1.52 Hz, 1H), 5.77 (s, 1H), 5.22 (s, 2H), 3.93 (s, 3H) as well as the di-benzylated methyl 3,5-bis(benzyloxy)-4-bromobenzoate (1.8 g).

1. extractionThe solution was extracted with 1:1 ethyl acetate/ether (6×)
2. washthe combined extracts were washed with water (8×), saturated sodium bicarbonate, brine
3. dry with materialdried over magnesium sulfate
4. concentrationconcentrated
5. customto provide an orange solid
6. stirringstirred overnight
7. customThe solid (primarily unreacted 4-bromo-3,5-dihydroxybenzoate) was removed by filtration
8. concentrationthe filtrate was concentrated
9. customto provide an orange oil which
10. customwas purified by column chromatography (80 g silica gel, 2:1 DCM in heptane elution, followed by DCM elution)