General procedure for the synthesis of 5-bromo-2-(bromomethyl)benzonitrile from 5-bromo-2-methylbenzonitrile: 5-bromo-2-methylbenzonitrile (10.0 g, 51.01 mmol), N-bromosuccinimide (NBS, 9.99 g, 56.11 mmol) and benzoyl peroxide (BPO, 0.62 g, 2.6 mmol) were reacted in carbon tetrachloride ( CCl4, 100 mL) The mixture was stirred and reacted at 80 °C for 8 h under nitrogen (N2) atmosphere. After completion of the reaction, the mixture was filtered and the filtrate was concentrated to dryness under reduced pressure. The crude product was purified by silica gel column chromatography with the eluent being a mixed solvent of ethyl acetate/petroleum ether (gradient elution, 0-100%) to afford 5-bromo-2-(bromomethyl)benzonitrile (9.8 g, 70% yield) as a light yellow oil.1H NMR (400 MHz, CDCl3) δ 7.80 (d, J = 2.0 Hz, 1H), 7.72 (dd, J = 8.4, 2.0 Hz, 1H), 7.43 (d, J = 8.4 Hz, 1H), 4.58 (s, 2H).
