1. m-Nitrobenzaldehyde (1 eq., 13.2 mmol, 2.0 g), 40% aqueous methylamine (1.1 eq., 14.5 mmol, 0.95 mL), and 3A molecular sieves (100 mg) were sequentially added to a screw-capped through-hole reaction vial.
2. The reaction mixture was heated at 80 °C for 24 hours.
3. After completion of the reaction, it was cooled to room temperature, the reaction mixture was diluted with chloroform (3 mL) and filtered to remove the molecular sieves.
4. The solvent was removed by rotary evaporation to obtain the crude product. The crude product was dissolved in methanol (30 mL) and cooled to 0°C.
5. Sodium borohydride (1.1 equiv, 14.5 mmol, 550 mg) was added in three batches and the reaction mixture was gradually warmed to room temperature and the reaction was continued for 24 hours.
6. Upon completion of the reaction, the reaction was quenched with 5% aqueous ammonium hydroxide (10 mL) and the solvent was removed by concentration by rotary evaporation.
7. The resulting aqueous layer was extracted with dichloromethane (3 x 10 mL) and the organic phases were combined.
8. The organic phase was dried with anhydrous sodium sulfate, filtered and the filtrate was concentrated by rotary evaporation.
9. The residue was purified by rapid chromatography on silica gel or distilled under vacuum to obtain the target product N-methyl-3-nitrobenzylamine.
