General procedure for the synthesis of 4-bromo-3,5-dimethylbenzonitrile from 2-bromo-5-(bromomethyl)-1,3-xylene: 2-bromo-5-(bromomethyl)-1,3-xylene (0.9 g, 3.24 mmol) was added to a 100 mL three-necked flask at room temperature. Ammonium hydroxide (4.41 g, 64.8 mmol) and iodine (0.8 g, 6.28 mmol) were added slowly under stirring. The reaction mixture was heated to 60 °C in acetonitrile (9 mL) under nitrogen protection and kept at this temperature for 4 hours. The progress of the reaction was monitored by TLC and the heating was stopped after confirming the complete reaction of the ingredients. The reaction mixture was cooled to room temperature (20-30 °C) and the solvent was removed by evaporation at 40 °C under reduced pressure. To the residue, 20 mL of ethyl acetate was added for liquid-liquid separation. The organic phase was washed sequentially with 10 mL of water and 10 mL of saturated aqueous sodium chloride. The organic phase was dried with anhydrous sodium sulfate and concentrated to give 0.7 g of 4-bromo-3,5-dimethylbenzonitrile crude as a light yellow waxy solid. The crude was recrystallized by 1 mL of isopropanol to give an off-white solid. Yield: 0.5 g, yield: 73.5%.
