反应详情

A mixture of 3,4-dihydroxybenzoic acid methyl ester (5.2 g, 31 mmol), 1,2-dibromoethane (2.9 mL, 34 mmol), and pulverized KOH (3.8 g, 68 mmol) in MeOH was heated at reflux for 30 hrs. After removal of the solvent under reduced pressure, the residue was partitioned between ethyl acetate and water. The ethyl acetate layer was washed with water, dried over MgSO4, concentrated in vacuo and purified by purified by column chromatography on silica gel eluting with 40% ethyl acetate in hexane to yield methyl 2,3-dihydrobenzo[b][1,4]dioxine-6-carboxylate (780 mg, 13%) along with the unreacted starting material (2.6 g). 1H NMR (DMSO-d6, 600 MHz) δ 7.45 (d, 1H, J=8.4 Hz), 7.39 (s, 1H), 6.96 (d, 1H, J=8.4 Hz), 4.33-4.28 (m, 4H), 3.80 (s, 3H); MS (ES+) m/z 195.1 (M+H)+

1. temperaturewas heated
2. temperatureat reflux for 30 hrs
3. customAfter removal of the solvent under reduced pressure
4. customthe residue was partitioned between ethyl acetate and water
5. washThe ethyl acetate layer was washed with water
6. dry with materialdried over MgSO4
7. concentrationconcentrated in vacuo
8. custompurified
9. customby purified by column chromatography on silica gel eluting with 40% ethyl acetate in hexane