General procedure for the synthesis of methyl 4-(bromomethyl)-3-nitrobenzoate from methyl 4-methyl-3-nitrobenzoate: in a 1000 mL round-bottomed flask, a nitrogen purge was performed first and an inert nitrogen atmosphere was maintained. Methyl 4-methyl-3-nitrobenzoate (10 g, 51.24 mmol, 1.00 eq.), N-bromosuccinimide (NBS, 9.13 g, 51.29 mmol, 1.00 eq.), benzoyl peroxide (BPO, 1.24 g, 5.12 mmol, 0.10 eq.), and carbon tetrachloride (400 mL) were added sequentially. The reaction mixture was stirred at 100 °C for 15 hours. After completion of the reaction, the crude product was purified by silica gel column chromatography with the eluent ethyl acetate/petroleum ether (gradient elution in the ratio of 0:1 to 1:9). Finally, 11.1 g of methyl 4-(bromomethyl)-3-nitrobenzoate was obtained in 79% yield, and the product was a yellow oil. The crude product obtained can be directly used in the next reaction without further purification.
