General procedure for the synthesis of 3-bromo-4-fluorobenzyl bromide from 3-bromo-4-fluorotoluene: 3-bromo-4-fluorotoluene (6 mL, 48 mmol) and N-bromosuccinimide (2.7 g, 15 mmol) were dissolved in 1,2-dichloroethane, followed by the addition of 2,2'-azobisisobutyronitrile (16 mg, 0.1 mmol) to a 1,2-dichloroethane solution ( 10 mL). The reaction mixture was heated to reflux for 2 hours. After completion of the reaction, it was cooled to room temperature, diluted with 1,2-dichloroethane (40 mL) and washed with water (2 x 50 mL). The organic phase was dried over anhydrous magnesium sulfate and concentrated to a small volume under reduced pressure. The product 3-bromo-4-fluorobenzyl bromide was obtained (yield: 9.2 g, 72% yield).
