General procedure for the synthesis of N-methyl-4-bromobenzylamine: In an autoclave, 4-bromobenzaldehyde (2.08 g, 11.55 mmol) was mixed with a methanolic solution of 2 M methylamine (25 mL, 33.44 mmol) and the reaction was stirred at 65 °C for 4 hours. After completion of the reaction, cooled to room temperature, sodium borohydride (633 mg, 16.72 mmol) was added in batches. Stirring was continued for 30 minutes at room temperature, followed by vacuum concentration. The residue was dissolved in ethyl acetate (30 mL) and the organic layer was washed with saturated aqueous sodium bicarbonate. The aqueous phase was adjusted to pH 13 with a few drops of 1 N sodium hydroxide solution and then extracted twice with ethyl acetate. The organic extracts were combined, washed with brine, dried over anhydrous magnesium sulfate, filtered and concentrated under reduced pressure to give N-methyl-4-bromobenzylamine as a colorless oil (2.04 g, 91% yield), which was used directly in the next step of the reaction.LC-MS analysis (Analytical Condition A, Zorbax SB-AQ columns, Acidic conditions): retention time t R = 0.61 min; [M + H]+ = 241.06 (acetonitrile adduct).
