To a stirred solution of ethyl 4-(2-(piperazin-1-yl)phenoxy)butanoate 25 (0.48 g, 0.0016 mol) in 60 mL acetonitrile was added DIEA (0.56 mL, 0.0032 mol) followed by 3-bromo-1-propanol 26 (0.14 mL, 0.0016 mol) and the resulting mixture was stirred at 60° C. for 6 h. The progress of the reaction was monitored by thin layer chromatography (TLC). The reaction mixture was concentrated and the residue was diluted with DCM (50 mL). The reaction mixture was washed with water (50 mL×2), dried over magnesium sulfate and evaporated. The residue was purified by silica gel column chromatography using 0-100% gradient of hexane and ethyl acetate to give the pure ethyl 4-(2-(4-(3-hydroxypropyl)piperazin-1-yl)phenoxy)butanoate 27. Brown oil, 0.39 g (63%). 1H NMR (400 MHz, CDCl3): δ 1.21 (t, J=7.2 Hz, 3H); 2.00 (quintet, J=7.2 Hz, 2H); 2.13 (quintet, J=7.2 Hz, 2H); 2.51 (t, J=7.2 Hz, 2H); 3.08 (broad s, 8H); 3.54 (t, J=6.4 Hz, 2H); 4.02 (t, J=6.4 Hz, 2H); 4.11 (q, J=7.2 Hz, 2H); 4.13-4.18 (m, 2H); 6.83-7.25 (m, 4H). MS (ESI): m/z=351.50 (M+H+).
