反应详情

A mixture of 2-hydroxy-3-nitrobenzaldehyde (4.3 g, 25.7 mmol), dimethyl 2-bromomalonate (5.95 g, 28.3 mmol), potassium carbonate (5.32 g, 38.6 mmol) and tetra-n-butylammonium bromide (0.8 g, 2.5 mmol) in toluene (100 mL) was heated at reflux with a Dean-Start trap for 5 hours. After cooling to room temperature, the mixture was evaporated and purified by silica gel chromatography (dichloromethane) to afford the product methyl 7-nitrobenzofuran-2-carboxylate (4.6 g, yield 81%). 1H NMR (400 MHz, CDCl3) δ ppm 8.31-8.33 (dd, 1H, J=1.2 Hz, 8.0 Hz), 8.02-8.04 (dd, 1H, J=1.2 Hz, 8.0 Hz), 7.66 (s, 1H), 7.46-7.50 (t, 1H, J=8.0 Hz), 4.03 (s, 3H).

1. temperaturewas heated
2. temperatureat reflux with a Dean-Start trap for 5 hours
3. customthe mixture was evaporated
4. custompurified by silica gel chromatography (dichloromethane)