The general procedure for the synthesis of 5-bromo-1,3-dichloro-2-methylbenzene from 3,5-dichloro-4-methylaniline was as follows: firstly, 3,5-dichloro-4-methylaniline was suspended in a mixture of 48% hydrobromic acid (5 mL) and deionized water (5 mL), and heated to close to the boiling point using a hot air gun. Subsequently, the reaction mixture was cooled to room temperature and further cooled to 0 °C in an ice/brine bath. At this temperature, a solution of sodium nitrite (109 mg, 1.58 mmol) dissolved in deionized water (2 mL) was slowly added dropwise. After the dropwise addition was completed, the reaction continued to be stirred in the cold bath for 15 min. Next, a solution of cuprous bromide (1.08 g, 7.53 mmol) dissolved in 48% hydrobromic acid (2 mL) was added, and the reaction mixture was stirred rapidly and heated to 50 °C and maintained at this temperature for 1 hour. After completion of the reaction, it was cooled to room temperature, the reaction mixture was diluted with ethyl acetate, and the aqueous layer was separated and discarded. The organic layer was washed sequentially with deionized water and saturated brine, dried with anhydrous magnesium sulfate, filtered through diatomaceous earth and concentrated under reduced pressure to obtain an orange residue. Finally, the residue was purified by silica gel column chromatography using hexane as eluent to give 164 mg (45% yield) of the target product 5-bromo-1,3-dichloro-2-methylbenzene as a yellow solid.
