A mixture of 1-[1-(4-nitrophenyl)piperidin-4-yl]piperazine monohydrochloride (1 g), oxetan-3-one (300 mg), sodium triacetoxyborohydride (1.02 g), dichloromethane (20 mL), acetic acid (1 mL), and chloroform (30 mL) was stirred at room temperature for 2 days. To the reactant were added a saturated aqueous sodium hydrogen carbonate solution and chloroform, followed by liquid separation. The organic phase was washed with saturated brine and dried over anhydrous magnesium sulfate, and then the solvent was evaporated under reduced pressure. The obtained residue was purified by silica gel column chromatography (eluent; chloroform:methanol=1:0-9:1) to obtain 1-[1-(4-nitrophenyl)piperidin-4-yl]-4-(oxetan-3-yl)piperazine (670 mg) as a yellow solid.
