A mixture of methyl {2-[(benzyloxy)methyl]aziridin-1-yl}acetate (0.4 g, 1.7 mmol), 4-fluorobenzylamine (0.38 g, 3.3 mmol), and boron trifluoride etherate (50 μL) was heated in a sealed glass tube at 95° C. for 68 h (Bull. Chem. Soc. Jpn., 1986, 59, 321). The resulting mixture was dissolved in dichloromethane (50 mL), cooled to 0° C., and treated with a mixture of triethylamine (0.95 mL, 6.8 mmol), DMAP (21 mg, 0.17 mmol), and acetic anhydride (0.48 mL, 5.1 mmol). The mixture was stirred at room temperature overnight, and extracted successively with saturated aqueous solution of sodium bicarbonate, dilute aqueous HCl, and brine. The organic extract was dried over anhydrous magnesium sulfate, filtered, and concentrated under vacuum. The residue was subjected to column chromatography on silica gel eluting with a mixture of 2% methanol in ethyl acetate. Collection and concentration of appropriate fractions provided the title piperazinone.
