General procedure for the synthesis of 2-fluoro-4-bromobenzyl bromide from 2-fluoro-4-bromotoluene: N-bromosuccinimide (NBS, 1.07 g, 6.05 mmol) and azobisisobutyronitrile (AIBN, 83 mg, 0.50 mmol) were dissolved in carbon tetrachloride (CCl4, 10 mL), followed by addition of 2-fluoro-4-bromotoluene (1 g, 5.04 mmol). The reaction mixture was heated to reflux at 100 °C for 13 hours. Upon completion of the reaction, the mixture was cooled to room temperature and the resulting solid was collected by filtration. The filtrate was extracted several times with carbon tetrachloride and water. The organic layers were combined and dried with anhydrous sodium sulfate to remove residual water. Subsequently, the organic layer was concentrated under reduced pressure to afford 4-bromo-1-(bromomethyl)-2-fluorobenzene (1.2 g, 4.47 mmol) in 89% yield. The product was characterized by 1H-NMR (300 MHz, CDCl3): δ 7.51-7.41 (m, 1H), 7.09 (d, J=9.0 Hz, 1H), 6.99 (d, J=8.2 Hz, 1H), 4.34 (s, 2H).
