To a solution of 1,4-bis(3-aminopropyl)piperazine (0.513 mL, 2.49 mmol) and 2-quinolinecarbaldehyde (823 mg, 5.24 mmol) in absolute ethanol (20 mL) was added 3 Å molecular sieves (5 g). After stirring the mixture for 12 h at room temperature, sodium borohydride (1.9 g, 49.9 mmol) was added and the mixture was stirred for 12 h at room temperature. Then the reaction mixture was quentched by dropwise addition of water (20 mL) and ethanol was removed under reduced pressure. The aqueous residue was extracted with CH2Cl2 (3×30 mL) and the combined organic layers were extracted with HCl 1N (2×50 mL). The combined aqueous layers were neutralized with NaOH 1N (50 mL) and extracted with CH2Cl2 (3×30 mL). The combined organic layers were dried over MgSO4, evaporated to dryness and the oily residue purified by flash chromatography (neutral aluminium oxide, CH2Cl2/MeOH: 90/10).
