The general procedure for the synthesis of methyl 2-(bromomethyl)-3-cyanobenzoate from methyl 3-cyano-2-methylbenzoate was as follows: under nitrogen protection, methyl 3-cyano-2-methylbenzoate (10.6 g, 60.5 mmol), N-bromosuccinimide (NBS) (16.2 g, 90.7 mmol), and azobisisobutyronitrile (AIBN) ( 100 mg) were suspended in tetrachloromethane (200 mL) and reacted at reflux for 6 hours. As an alternative, benzoyl peroxide can be used as a catalyst for the bromination reaction in benzene. The progress of the reaction was monitored by thin layer chromatography (TLC) (unfolding agent: hexane solution of 10% ethyl acetate) to confirm complete consumption of the feedstock. After completion of the reaction, the reaction mixture was filtered and the filter cake was washed with chloroform (3 x 20 mL). The filtrate and washings were combined and concentrated under reduced pressure. The residue was purified by short silica gel column chromatography using a hexane solution of 10% ethyl acetate as eluent. The eluate containing the target product was collected and concentrated under reduced pressure, and the resulting product was dried overnight under vacuum to afford methyl 2-(bromomethyl)-3-cyanobenzoate 15.1 g in 98% yield. 1H NMR data of the product (DMSO-d6): δ 8.15 (d, J = 8.0 Hz, 1H); 8.12 (d, J = 7.9 Hz, 1H); 7.67 (t, 1H); 5.04 (s, 2H); 3.89 (s, 3H).
