反应详情

To a solution of LiOAc.2H2O (0.16 g, 1.62 mmol) in 97:3 CH3CN/H2O (30 mL) was added 6-chloro-2H-1-benzopyran-3-carboxylic acid (1.43 g, 8.12 mmol), followed by NBS (1.52 g, 8.53 mmol) and the mixture was stirred at room temperature for 5 hours. The reaction mixture was then concentrated to dryness under reduced pressure. Purification by flash column chromatography (gradient, hexanes, then 98:2 to 90:10 hexanes/Et2O) gave 3-bromo-6-chloro-2H-chromene (0.47 g, 27%) as a pale yellow oil: 1H NMR (300 MHz, CDCl3) δ 7.14-7.10 (m, 1H), 6.94-6.88 (m, 2H), 6.79 (d, J=8.1 Hz, 1H), 6.75 (s, 1H), 4.88 (d, J=1.5 Hz, 2H).

1. concentrationThe reaction mixture was then concentrated to dryness under reduced pressure
2. customPurification by flash column chromatography (gradient, hexanes