Step B: At room temperature, 3-bromobenzaldehyde (47.5 mL, 0.4 mol) was dissolved in methanol (460 mL), followed by the addition of an aqueous solution of methylamine (35 mL, 0.4 mol, 40 wt% solution). The reaction mixture was cooled to 0 °C and sodium borohydride (22 g, 0.6 mol) was added in batches. The reaction mixture was kept stirred at 0 °C for 3.5 h and then gradually warmed up to room temperature. After completion of the reaction, the mixture was concentrated under reduced pressure and subsequently partitioned with dichloromethane and water. The aqueous layer was separated and washed with dichloromethane (3×). The organic phases were combined and washed sequentially with saturated sodium bicarbonate solution and brine, then dried over anhydrous magnesium sulfate. After filtration, the organic phase was concentrated under reduced pressure to afford the target product N-methyl-3-bromobenzylamine (76 g, 81%) as a clear oil. The product was characterized by 1H NMR (300 MHz, CDCl3): δ 7.48 (d, J = 1.5 Hz, 1H), 7.40-7.37 (m, 1H), 7.24-7.16 (m, 2H), 3.73 (s, 2H), 2.45 (s, 3H).
