General procedure for the synthesis of 3,5-dinitrobromobenzene from 1,3-dinitrobenzene: 30.0 g of 1,3-dinitrobenzene (0.18 mol) was dissolved in 180 mL of concentrated sulfuric acid, and heated to 80°C, maintaining the reaction temperature between 80-90°C. The reaction was carried out in 9 batches. 44.5 g of N-bromosuccinimide (NBS, 0.25 mol) was added to the above solution in 9 batches and the reaction lasted for 30 min. After completion of the reaction, it was cooled to room temperature and the reaction mixture was poured into 600 mL of ice water, and a white precipitate was precipitated. After filtration, washing and drying, 41.3 g of white solid 3,5-dinitrobromobenzene was obtained in 93.7% yield.
Preparation of sodium solution in methanol: 1 g of sodium (43.4 mmol) was dissolved in methanol. 8.7 g of 3,5-dinitrobromobenzene (35.2 mmol) was added to the above sodium methanol solution and the reaction was carried out at reflux for 2 hours at 45°C. After the reaction was completed, it was cooled to room temperature. Upon completion of the reaction, it was cooled to room temperature and neutralized with 50 mL of 1N hydrochloric acid solution, followed by extraction with dichloromethane. The organic phases were combined, washed three times with saturated brine and dried over anhydrous magnesium sulfate. After filtration, the solvent was evaporated and the crude product was purified by column chromatography (petroleum ether:dichloromethane=5:1) to give 4.6 g of 3-methoxy-5-nitrobromobenzene as a white powdery solid in 56.3% yield.
400 mg of Pd/C catalyst was added to a solution of 2.32 g of 3-methoxy-5-nitrobromobenzene (10 mmol) dissolved in 25 mL of methanol, 10 mL of acetone was added, and the reaction was carried out by passing hydrogen for 3 hours at room temperature. After completion of the reaction, the Pd/C catalyst was removed by filtration, the solvent was evaporated, and the crude product was purified by column chromatography (petroleum ether:ethyl acetate=4:1) to give 1.95 g of light yellow solid in 96.5% yield.
