99-51-4

22162-22-7

The general procedure for the synthesis of 1-bromo-2,3-dimethyl-5-nitrobenzene from 4-nitro-o-xylene was as follows: 1. To a stirred solution of 1,2-dimethyl-4-nitrobenzene (CAS No. 99-51-4, purchased from TCI chemicals, 25 g, 165.4 mmol) in dichloromethane (DCM, 300 ml) was slowly added anhydrous aluminum trichloride (AlCl3, 55.13 g, 413.4 mmol) at 0 °C. 2. the reaction mixture was continued to be stirred at 0 °C for 50 min. 3. Bromine (Br2, 31.72 g, 198.4 mmol) was added dropwise to the reaction mixture at 0 °C. 4. the reaction mixture was warmed to 40 °C and stirred at this temperature for 48 hours. 5. Upon completion of the reaction, the mixture was cooled to room temperature and combined with another batch of reaction mixture prepared by the same method on the same scale. 6. The reaction was quenched by slow addition of saturated sodium thiosulfate (Na2S2O3-5H2O) solution until the reaction mixture was neutralized. 7. Extract the reaction mixture with dichloromethane (DCM, 3 x 500 ml). 8. Combine the organic phases and wash with brine (500 ml). 9. Separate the organic phase, dry with anhydrous sodium sulfate (Na2SO4), filter and concentrate under reduced pressure. 10. The residue was purified by column chromatography (using 100% hexane as eluent) to afford the target product 1-bromo-2,3-dimethyl-5-nitrobenzene (56.0 g, 243.4 mmol). The product nuclear magnetic resonance hydrogen spectrum (NMR, 400 MHz, DMSO-d6) data were as follows: δ 8.23 (d, J = 2.0 Hz, 1H), 7.99 (d, J = 1.6 Hz, 1H), 2.44 (s, 3H), 2.42 (s, 3H).