General procedure for the synthesis of (4-methylpiperazin-1-yl)(4-nitrophenyl)methanone from N-methylpiperazine and 4-nitrobenzoyl chloride: 4-nitrobenzoyl chloride (1 g, 5.39 mmol) was dissolved in acetonitrile (50 mL), cooled to 10 °C and then 1-methylpiperazine was slowly added. The reaction mixture was stirred at this temperature for 10 minutes, followed by continued stirring for 1 hour. Then, triethylamine (1.49 mL, 10.78 mmol) was added and stirring was continued for half an hour. After completion of the reaction, the mixture was diluted with ice-cold water (150 mL) and extracted with ethyl acetate (4 x 150 mL). The organic layers were combined, dried with anhydrous magnesium sulfate and concentrated under reduced pressure to give the yellow solid product (4-methylpiperazin-1-yl)(4-nitrophenyl)methanone (1.1 g, 82% yield). Thin-layer chromatography (TLC) analytical conditions: 10% methanol/dichloromethane, Rf=0.6. Nuclear magnetic resonance hydrogen spectrum (1H NMR, 400MHz, CDCl3) δ: 8.28 (d, J=8.5Hz, 2H), 7.56 (d, J=8.5Hz, 2H), 3.88 (broad single peak, 4H), 3.46 (broad single peak, 4H), 2.40 (s , 3H). Electrospray mass spectrometry (ESI/MS) m/z: 250.0 (M+H).
