GENERAL STEPS: To a solution of 1-(tert-butoxycarbonyl)pyrrolidin-3-one (74 g, 0.4 mol) in methanol (450 mL) was slowly added a methanolic solution of methylamine (137.8 g, 1.2 mol) at 0 °C. The reaction mixture was stirred at room temperature for 2 hours. Subsequently, sodium borohydride (15.2 g, 0.4 mol) was added in batches and stirring was continued for 1 hour at room temperature. Upon completion of the reaction, the mixture was concentrated under reduced pressure to remove the solvent to give the crude product. The crude product was extracted by partitioning between dichloromethane (3 x 500 mL) and water (300 mL). The organic layers were combined, dried with anhydrous sodium sulfate, filtered and concentrated under reduced pressure to afford 1-(tert-butoxycarbonyl)-3-methylaminopyrrolidine (74 g, 92.5% yield), which could be used in the next reaction without further purification. The structure of the product was confirmed by 1H NMR (400 MHz, CDCl3): δ 3.54 (m, 4H), 3.29 (m, 2H), 2.45 (s, 3H), 2.20 (m, 1H), 1.38 (s, 9H).
