Step 1: N-methylethylenediamine (11.8 mL, 134.9 mmol) was dissolved in acetonitrile (300 mL) and cooled to -30 °C. Subsequently, triethylamine (TEA, 7.46 mL, 53.9 mmol) was added to this solution, followed by dropwise addition of di-tert-butyl dicarbonate (Boc2O, 9.81 g, 45 mmol) in acetonitrile solution. The reaction mixture was stirred at room temperature for 2 hours. After completion of the reaction, the insoluble material was removed by Celite filtration. The filtrate was purified by silica gel column chromatography (elution gradient: 1:50→1:20→1:10 ethyl acetate/hexane) to afford tert-butyl N-(2-aminoethyl)-N-methylcarbamate (CXVIII) as a yellow oil (5.2 g, 29.9 mmol, 66% yield). The product was confirmed by electrospray ionization mass spectrometry (ESIMS) with molecular formula C8H18N2O2, m/z 175 (M + H).
