1. 1,2,4,5-tetramethylbenzene (25.0 g, 0.18 mol) and 150 mL of methylene chloride were added to a dry three-necked flask with stirring until completely dissolved. 2. Iodine (I2, 1.0 g, 3.94 mmol) was added to the solution as a catalyst. 3. Under stirring, bromine (Br2, 24 mL, 74.6 g, 0.47 mol) dissolved in a 100 mL of dichloromethane. 4. After the dropwise addition was completed, the reaction mixture was heated to reflux and held for 1.5 h. 5. After the reaction was completed, it was cooled to room temperature and the reaction was quenched by the addition of 5 M aqueous sodium hydroxide (50 mL). 6. The solid product was collected by filtration, washed with deionized water, and dried to afford 1,4-dibromo-2,3,5,6-tetramethylbenzene in 93% yield ( The product was characterized by 1H NMR (500 MHz, CDCl3) and 13C NMR (125.68 MHz, CDCl3): 1H NMR δ 2.48 (s, 12H); 13C NMR δ 135.2, 128.3, 22.4. 8. The 1H NMR spectrum and structure of the product are shown in Figure 1.
