A 1.3 M solution of methyl lithium ether (35 mL) was slowly added dropwise to an ether solution of 3-bromo-5-fluorobenzoic acid (5 g) at -78 °C, maintaining the temperature at -78 °C. The reaction mixture was then slowly warmed to -10 °C and stirred continuously at this temperature for 1 hour. Upon completion of the reaction, the reaction was carefully quenched with saturated ammonium chloride solution (100 mL) until the pH of the reaction system reached 3. The product was extracted with ether (2 x 100 mL), and the combined organic phases were dried over anhydrous sodium sulfate. The solvent was removed by evaporation under reduced pressure to give 1-(3-bromo-5-fluorophenyl)ethanone as an off-white solid (4.67 g, 94% yield). The product was characterized by 1H NMR (CDCl3): δ 2.59 (3H, s, ArCOCH3), 7.44 (1H, dd, Ar), 7.59 (1H, dd, Ar), 7.87 (1H, s, Ar).
