反应详情

温度

-78 °C

The ethyl 7-methoxy-8-methyl-2-(trifluoromethyl)-2H-chromene-3-carboxylate from Example 3a, Step 2 (3.0 g, 9.49 mmole) was dissolved in methylene chloride (120 mL). The solution was chilled to −78° C. and BBr3 (94.9 mL, 1 M solution in CH2Cl2) was added slowly to the above solution. The reaction was slowly warmed to room temperature and stirred overnight. The reaction was cooled to −78° C. and MeOH (30 mL) added in. After the solution was stirred at room temperature for 2 h, the reaction was evaporated to dryness to give a brownish solid having ca.90% purity. The crude product was further purified by passing through a silica plug to give a yellow solid (2.7 g, 80%): LCMS m/z 311.05 (M+Na). 1H NMR (acetone-d6/400 MHz) 9.11 (s, 1H), 7.75 (s, 1H), 7.11(d, 1H, J=8.4 Hz), 6.59 (d, 1H, J=8.4 Hz), 5.78 (q, 1H, J=6 Hz), 3.79 (s, 3H), 2.09(s, 3H).

1. temperatureThe reaction was slowly warmed to room temperature
2. temperatureThe reaction was cooled to −78° C.
3. stirringAfter the solution was stirred at room temperature for 2 h
4. customthe reaction was evaporated to dryness
5. customto give a brownish solid
6. customThe crude product was further purified