tert-Butyl 2-amino-4-(4-methylpiperazin-1-yl)benzoate (1.5 g, 5.15 mmol) was dissolved in dry dioxane (25 mL) under a nitrogen atmosphere. N-ethoxycarbonylpiperidone (1.06 g, 0.932 mL, 6.18 mmol, 1.2 eq) was added, followed by trifluoroacetic acid (1.03 mL, 13.39 mmol, 2.6 eq) and sodium triacetoxyborohydride (1.72 g, 7.73 mmol, 1.5 eq). The mixture was stirred at room temperature for 4 hours. A saturated aqueous solution of NaHCO3 was then added, the mixture was concentrated under reduced pressure and extracted with dichloromethane (3×40 mL). The combined organic layers were washed with brine, dried over Na2SO4 and concentrated under reduced pressure. After purification by chromatography over silica gel (DCM/EtOH 93:7) 2.187 g of title compound were obtained as a white solid (95% yield).
