Under nitrogen protection, 4-bromo-2-methylbenzonitrile (3.0 g, 15 mmol) was dissolved in anhydrous tetrahydrofuran (20 mL) and cooled to 0 °C. A tetrahydrofuran solution (46 mL) of 1.0 M borane was added slowly, keeping the reaction temperature at 0 °C. The reaction mixture was stirred at 0 °C for 1 h before being warmed to 80 °C and heated overnight. Upon completion of the reaction, the mixture was cooled to 0 °C and the reaction was quenched by slow addition of methanol and subsequently concentrated under vacuum. The crude product was treated with ethyl acetate (20 mL) and a 1,4-dioxane solution (8.0 mL, 32 mmol) of 4 M hydrochloric acid for 5 min. The solid was collected by filtration, washed with ether and dried to give 4-bromo-2-methylbenzenemethanamine as a white powder (3.24 g, yield: 100%). Liquid chromatography-mass spectrometry (LCMS) analysis: retention time (RT) 0.75 min, molecular ion peak (MH+) 200.0. nuclear magnetic resonance hydrogen spectrum (1H NMR, 300 MHz, DMSO-d6) δ: 8.28 (broad single peak, 2H), 7.42-7.54 (multiple peaks, 2H), 7.34 (double peak, J = 7.93 Hz, 1H) , 3.99 (double peak, J = 4.15 Hz, 2H), 2.35 (single peak, 3H).
