Synthesis
The general procedure for the synthesis of 2-bromo-5-chlorobenzyl bromide from 2-bromo-5-chlorotoluene was as follows: 20.5 g (100 mmol) of 2-bromo-5-chlorotoluene was dissolved in 200 mL of carbon tetrachloride, followed by the addition of 0.2 g (1 mmol) of AIBN (azobisisobutyronitrile) and 19.6 g (110 mmol) of N-bromosuccinimide (NBS). The resulting mixture was refluxed for 2 h and then cooled to room temperature. The reaction mixture was sequentially washed twice with 50 mL of water, then with 50 mL of brine solution and finally dried with anhydrous magnesium sulfate. The solvent was removed by distillation under reduced pressure to give an oil containing a small amount of unreacted material. The oily substance was dissolved in 20 mL of hexane and recrystallized at room temperature to give 22.7 g (80% yield) of 2-bromo-1-bromomethyl-5-chlorobenzene. The product was characterized by 1H NMR (300 MHz, CDCl3): δ 7.50 (d, 1H, J = 8.7 Hz), 7.45 (d, 1H, J = 2.4 Hz), 7.15 (dd, 1H, J = 8.7 Hz, 2.4 Hz), 4.53 (s, 2H).
References
[1] Organic and Biomolecular Chemistry, 2012, vol. 10, # 31, p. 6404 - 6409
[2] Patent: WO2005/123054, 2005, A1. Location in patent: Page/Page column 25
[3] Patent: WO2006/46030, 2006, A2. Location in patent: Page/Page column 28
[4] Organic Letters, 2015, vol. 17, # 19, p. 4654 - 4657
[5] Journal of the Chemical Society - Perkin Transactions 1, 1997, # 19, p. 2903 - 2909
