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To a suspension of 4-bromo-3-fluorobenzoic acid (15.0 g) in anhydrous ethanol (230 mL) was slowly added concentrated sulfuric acid (8.0 mL). The reaction mixture was placed in a 60°C oil bath and stirred for 66 hours. After completion of the reaction, it was cooled to room temperature and the solvent was removed by rotary evaporator under reduced pressure. The residue was washed with 1 N sodium hydroxide solution (70 mL) and subsequently extracted with ethyl acetate (500 mL). The organic phase was washed sequentially with water (250 mL) and saturated saline (250 mL), dried over anhydrous magnesium sulfate, filtered and concentrated under reduced pressure. Ethyl 4-bromo-3-fluorobenzoate was obtained as a light yellow solid (17.0 g, quantitative yield). Mass spectral analysis showed M/Z (M [79 Br] + H)+ = 247.

[1] Patent: EP2210891, 2010, A1. Location in patent: Page/Page column 17-18
[2] Journal of Medicinal Chemistry, 2009, vol. 52, # 6, p. 1540 - 1545