Benzaldehyde → N-Benzyl-N'-boc-ethylenediamine

To a solution of tert-butyl 2-aminoethylcarbamate (6.4 g, 40.0 mmol) in methanol (60 mL) was added benzaldehyde (4.7 g, 44.0 mmol) and molecular sieve 3 Å. After stirring at ambient temperature overnight, the mixture was cooled down to ca. −10° C. (ice/salt bath) and treated portion wise with NaBH4 (9.1 g, 240.0 mmol) over 30 min. After complete addition, the bath was removed and the reaction mixture stirred at ambient temperature for 16 h. The solvent was evaporated and the residue taken into EtOAc (150 mL) and poured into water (100 mL). The organic layer was extracted with 0.5 N HCl (3×100 mL). The combined aqueous solution was cooled to 0° C., basified with sat. NaHCO3 and extracted with CHCl3 (3×100 mL). The combined organic layers were washed with brine (200 mL). After drying over MgSO4 and filtering, the solvent was evaporated in vacuo to give compound A (9.2 g, 36.8 mmol, 92%) as a colorless oil. LC-MS [M+H] 251.2 (C14H22N2O2+H, calc: 251.3). TLC Rf (DCM/MeOH 9:1): 0.30. Compound A was used without further purification.