Hydrobromic acid (24.37 mL) was added dropwise to a solution of 5-amino-2-isobutylbenzonitrile (34 g) in acetonitrile (500 mL) at 0 °C, followed by the slow addition of an aqueous solution of sodium nitrite (16.16 g) (50 mL). The reaction mixture was stirred for 30 min and then copper (II) bromide (87 g) and copper (I) bromide (5.60 g) were added. The reaction mixture was stirred continuously for 16 hours at room temperature. After completion of the reaction, the reaction was quenched with saturated aqueous sodium bicarbonate solution. The reaction mixture was extracted with ethyl acetate (EA), the organic phases were combined and dried over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by silica gel column chromatography to afford 5-bromo-2-isobutylbenzonitrile (36 g) as a colorless oil. δH (CDCl3, 400 MHz): 0.96 (6H, d), 1.98 (1H, m), 2.69 (2H, d), 7.18 (1H, d), 7.64 (1H, dd), 7.55 (1H, d).
