反应详情

To a solution of the product obtained from step A (640 mg, 1.76 mmol) in dichloromethane (5 mL) at 0° C. was added diisopropylethylamine (0.61 mL, 3.53 mmol) followed by ethyl chloroformate (0.34 mL, 3.53 mmol). The reaction mixture was allowed to warm to ambient temperature over 2 h before addition of water (10 mL). The mixture was extracted with dichloromethane (2×20 mL) and the combined organic extracts washed with brine, dried over Na2SO4, filtered and the filtrate concentrated in vacuo. Purification by flash column chromatography (SiO2, 9:1 to 1:1 hexanes/ethyl acetate) afforded ethyl 2-(5-bromo-7-chlorobenzofuran-2-yl)ethyl(2,2-dimethoxyethyl)carbamate (685 mg, 89%) as a colorless oil: 1H NMR (CDCl3, 300 MHz) δ 7.51 (s, 1H), 7.37 (s, 1H), 6.50-6.39 (m, 1H), 4.53-4.38 (m, 1H), 4.21-3.98 (m, 2H), 3.75-3.64 (m, 2H), 3.47-3.35 (m, 6H), 3.34-3.22 (m, 2H), 3.13-2.99 (m, 2H), 1.30-1.11 (m, 3H).

1. extractionThe mixture was extracted with dichloromethane (2×20 mL)
2. washthe combined organic extracts washed with brine
3. dry with materialdried over Na2SO4
4. filtrationfiltered
5. concentrationthe filtrate concentrated in vacuo
6. customPurification by flash column chromatography (SiO2, 9:1 to 1:1 hexanes/ethyl acetate)