反应详情

BBr3 (4.72 g, 1.78 ml, 18.9 mmol) was carefully added through a syringe over 5 min to a stirred solution of dimethoxy acid 4c (1.35 g, 4.7 mmol) in anhydrous CH2Cl2 (20 ml). Resulted mixture was magnetically stirred for 8 h and concentrated under vacuum. The residue was co-evaporated with toluene (2×20 ml), dissolved in methanol (20 ml) and HCl gas was bubbled into the solution for 2 min. The material obtained after evaporation of the solvent was partitioned between cold water (30 ml) and ethyl acetate (100 ml). The organic phase was washed with saturated NaHCO3 (2×10 ml), brine (20 ml), dried over MgSO4 and concentrated. The resultant crude product was chromatographed on a short silica gel column eluting with ethyl acetate. Pure product fractions were concentrated to afford 1.2 g (94%) of 5c as a tan oil. 1H NMR(DMSO-d6): δ 8.95 (s, 1H), 7.82 (s, 1H), 7.24-7.36 (m, 5H), 6.83 (d, J=8.2 Hz, 1H), 6.38 (d, J=8.2 Hz, 1H), 3.59 (s, 3H), 2.75 (t, J=8.0 Hz, 2H), 2.52 (t, J=8.0 Hz, 2).

1. customResulted mixture
2. concentrationconcentrated under vacuum
3. dissolutiondissolved in methanol (20 ml)
4. customHCl gas was bubbled into the solution for 2 min
5. customThe material obtained
6. customafter evaporation of the solvent
7. customwas partitioned between cold water (30 ml) and ethyl acetate (100 ml)
8. washThe organic phase was washed with saturated NaHCO3 (2×10 ml), brine (20 ml)
9. dry with materialdried over MgSO4
10. concentrationconcentrated
11. customThe resultant crude product was chromatographed on a short silica gel column
12. washeluting with ethyl acetate
13. concentrationPure product fractions were concentrated