In a 100 mL round-bottomed flask, 3-methoxy-5-methylbenzonitrile (500 mg, 3.39 mmol) was dissolved in 15 mL of anhydrous dichloromethane (DCM), followed by the addition of tetrabutylammonium iodide (1.38 g, 3.73 mmol, 3.5 equiv). The reaction system was cooled to -78 °C. Boron tribromide (1 M solution of DCM, 11.87 mL, 33.16 mmol) was added slowly and dropwise at low temperature. The reaction mixture was stirred at -78 °C and then gradually warmed to room temperature and stirred overnight. Upon completion of the reaction, the reaction was quenched with ice water and neutralized with saturated sodium bicarbonate (NaHCO3) solution. The reaction mixture was extracted with dichloromethane (DCM). The organic layers were combined, concentrated and purified by silica gel column chromatography (eluent: 0-10% methanol/DCM) to give a light yellow solid product (408 mg, 90% yield). Liquid chromatography-mass spectrometry (LC-MS) analysis showed a molecular ion peak m/z 132.0 ([M-1]-). Nuclear magnetic resonance hydrogen spectroscopy (1H NMR, 300 MHz, CDCl3) data were as follows: δ 7.20 (s, 1H), 6.96 (s, 1H), 6.91 (s, 1H), 2.37 (s, 3H).
