Hydrochloric Acid → [(2,4-Dimethoxyphenyl)methyl](methyl)amine

2,4-Dimethoxybenzaldehyde (5.0 g) was dissolved in methanol (60 mL), and a 40% methanol solution (9.3 mL) of methylamine was added at room temperature. The mixture was stirred at room temperature for 1 hr, and sodium borohydride (1.37 g) was added by small portions under ice-cooling. The mixture was stirred at room temperature for 3 hr, treated with 1 mol/L hydrochloric acid under ice-cooling, and methanol was evaporated under reduced pressure. The residue was diluted with ethyl acetate, basified with saturated aqueous sodium hydrogen carbonate solution, and extracted with ethyl acetate. The extract was washed with saturated brine, dried over anhydrous sodium sulfate, and concentrated under reduced pressure. The residue was purified by basic silica gel column chromatography (eluent: hexane:ethyl acetate=4:1→2:1) to give the title compound as a colorless oil (yield 4.41 g, 81%).