反应详情

To a solution of 4-methoxy-2-methyl-benzoic acid methyl ester (1.47 g, 8.16 mmol, 1.0 equiv; commercially available) in CCl4 (15 mL) was added N-bromosuccinimide (1.60 g, 8.97 mmol, 1.1 equiv) and dibenzoyl peroxide (0.198 g, 0.45 mmol, 0.05 equiv). The mixture was heated to reflux for 1.5 h, when TLC indicated that still some starling material was left. Therefore, additional N-bromosuccinimide (0.16 g, 0.90 mmol, 0.11 equiv) and dibenzoyl peroxide (0.080 g, 0.41 mmol, 0.18 equiv) was added and heating continued for 1 h. The reaction mixture was cooled down, poured on crashed ice, extracted with ethyl acetate, the combined organic phases washed with a sat. solution of NaCl, dried over Na2SO4 and concentrated by evaporation under reduced pressure. The crude material was purified with silica column chromatography eluting with hexane/ethyl acetate (95:5) affording 1.43 g (68%) of the title compound as yellow crystals. 1H NMR (300 MHz, CDCl3): δ 3.87 (s, 3H), 3.91 (s, 3H), 4.97 (s, 2H), 6.86 (dd, J=8.7 Hz, J=2.7 Hz, 1H), 6.97 (d, J=2.7 Hz, 1H), 7.99 (d, J=8.7 Hz, 1H).

1. temperatureThe mixture was heated
2. temperatureto reflux for 1.5 h
3. waitwas left
4. temperatureheating
5. temperatureThe reaction mixture was cooled down
6. additionpoured
7. extractionextracted with ethyl acetate
8. washthe combined organic phases washed with a sat. solution of NaCl
9. dry with materialdried over Na2SO4
10. concentrationconcentrated by evaporation under reduced pressure
11. customThe crude material was purified with silica column chromatography
12. washeluting with hexane/ethyl acetate (95:5)