a) Synthesis of methyl 3-bromo-4-fluorobenzoate
3-Bromo-4-fluorobenzoic acid (3.33 g, 15.2 mmol) was dissolved in methanol (30 mL) and acetyl chloride (4.3 mL, 60.8 mmol) was added slowly and dropwise under cooling in an ice bath. The reaction mixture was stirred at room temperature for 20 hours. After completion of the reaction, the reaction solution was concentrated under reduced pressure. The crude product was purified by silica gel column chromatography (eluent: hexane/ethyl acetate) to afford methyl 3-bromo-4-fluorobenzoate (3.2 g, 90% yield) as a colorless oil.1H-NMR (CDCl3) δ: 3.92 (3H, s), 7.18 (1H, dd, J = 8.0, 8.2 Hz), 7.99 (1H, ddd, J = 1.9, 4.9, 8.0 Hz), 7.99 (1H, ddd, J = 1.9, 4.9, 8.0 Hz). 4.9, 8.0 Hz), 8.27 (1H, dd, J = 1.9, 6.5 Hz).
