General procedure for the synthesis of 1-bromo-3,4-dimethoxy-2-methylbenzene from 2,3-dimethoxytoluene: To a solution of 2,3-dimethoxytoluene (55 g, 361.8 mmol) in acetonitrile (ACN, 1.8 L) was added N-bromosuccinimide (NBS, 65.3 g, 369 mmol) in batches, and the reaction was stirred under nitrogen protection at room temperature. The mixture was stirred for 24 hours at room temperature under nitrogen protection. After completion of the reaction, the reaction mixture was diluted with ethyl acetate, washed sequentially with saturated aqueous sodium bicarbonate (NaHCO3) and water, and the organic phase was dried with anhydrous sodium sulfate (Na2SO4). The solvent was concentrated under reduced pressure and the resulting crude product was recrystallized from methanol (MeOH) to give pure 1-bromo-3,4-dimethoxy-2-methylbenzene as a white solid (67 g, 80% yield). The structure of the product was analyzed by 1H NMR (CDCl3, 400 MHz) δ7.22 (d, J = 8.8 Hz, 1H), 6.64 (d, J = 8.8 Hz, 1H), 3.82 (s, 3H), 3.76 (s, 3H), 2.32 (s, 3H) and 13C NMR (CDCl3, 100 MHz): δ152.1, 148.0, 132.2, 127.2, 116.0, 110.9, 60.3, 55.8, 16.0 confirmed; GC-MS showed molecular ion peak m/z 230 [M+] as expected.
