A solution of (4-(2-amino-4-nitrophenyl)piperazin-1-yl)(phenyl)methanone (0.4 g, 1.2 mmol) and benzaldehyde (0.18 ml, 1.8 mmol) in 15 ml dichloroethane was stirred for 10 min, followed by the addition of sodium triacetoxyborohydride (0.78 g, 3.68 mmol). The mixture was stirred overnight under argon atmosphere. The reaction was quenched with water and extracted with ethyl acetate (3×20 ml), followed by drying over anhydrous sodium sulfate. N-benzyl-2-(4-benzoylpiperazin-1-yl)-5-nitrobenzenamine (0.1 g, 19%) was obtained by flash column chromatograph (50% ethyl acetate in hexanes). 1H NMR (500 MHz, CDCl3) δ (ppm) 3.00-3.60 (d, br, 8H), 4.44 (d, J=5.5 Hz, 2H), 5.04 (t, J=5.5 Hz, 1H), 7.06 (d, J=8.6 Hz, 1H), 7.34-7.65 (m, 11H), 7.67 (dd, J=8.6, 2.5 Hz, 1H). 13C NMR (125 MHz, CDCl3): δ (ppm) 48.6, 51.3, 105.5, 113.6, 119.3, 127.6, 127.7, 128.2, 129.1, 129.4, 130.5, 135.9, 138.7, 143.4, 144.3, 146.0, 171.1.
