Synthesis
2-Bromo-5-fluorophenol (228.00 g, 1.19 mol) was mixed with potassium carbonate (247.47 g, 1.79 mol) in N,N-dimethylformamide (3.00 L), 2-bromo-1,1-diethoxyethane (197.54 mL, 1.31 mol) was added, and the reaction was carried out for 7 hours at 135 °C. After completion of the reaction, the mixture was concentrated in vacuum and extracted with ethyl acetate (3 x 2 L). The organic layers were combined, washed with 2 M aqueous NaOH (4 L), dried over MgSO4 and filtered, and concentrated in vacuum to afford 1-bromo-2-(2,2-diethoxyethoxy)-4-fluorobenzene (362.00 g, 98% yield), which was used directly in the next step.1H NMR (400 MHz, D6-DMSO) δ 7.58 (d, 1H, J = 6.8 and 8.8 Hz), 7.11 (dd, 1H, J = 2.8 and 10.8 Hz), 6.76 (dt, 1H, J = 2.2 and 8.1 Hz), 4.81 (t, 1H, J = 5.1 Hz), 4.03 (d, 2H, J = 5.1 Hz), 3.73-3.56 (m, 4H), 1.13 (t, 6H, J = 6.6 Hz). 1-Bromo-2-(2,2-diethoxyethoxy)-4-fluorobenzene (352.00 g, 1.15 mol) was dissolved in toluene (2500 mL), polyphosphoric acid (370.00 g, 3.4 mol) was added, and heated to reflux for 5 hours. The reaction mixture was concentrated in vacuum, diluted with water (3 L) and extracted with ethyl acetate (4 L). The organic layer was washed with aqueous NaOH (2 L), filtered and concentrated in vacuum, and purified by distillation under reduced pressure to give 7-bromo-4-fluorobenzofuran (125.00 g, 51% yield) with a boiling point of 80 °C (1 mmHg) as a colorless liquid, solidified at room temperature.1H NMR (400 MHz, CDCl3) δ 7.67 (d, 1H, J = 2.2 Hz), 7.39 (dd, 1H, J = 5.1 and 3.7 Hz), 6.94 (d, 1H, J = 2.2 Hz), 6.86 (t, 1H, J = 8.8 Hz).
