General procedure for the synthesis of 2-bromo-6-chlorobenzyl bromide (compound [5-2]) from 2-bromo-6-chlorotoluene: 2-bromo-6-chlorotoluene (1.58 g) was dissolved in 15 mL of carbon tetrachloride, and N-bromosuccinimide (1.63 g) and 2,2'-azino-bis (isobutyronitrile) (125 mg) were added. The reaction mixture was heated to reflux for 24 hours. After completion of the reaction, the reaction was quenched with water and the mixture was extracted with chloroform. The organic layers were combined, dried over anhydrous sodium sulfate, filtered and the filtrate concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography to afford 2-bromo-6-chlorobenzyl bromide (2.16 g) as a white solid.1H-NMR (400 MHz, CDCl3) δ: 7.51 (1H, d, J = 8.1 Hz), 7.37 (1H, d, J = 8.1 Hz), 7.11 (1H, d, J = 8.1 Hz), 4.80 (2H, s) .
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