To a 50 mL dry three-necked flask, 0.554 g (0.002 mol) of self-made 2-[4-(3,6-dichloro-pyridazin-4-yl)-piperazin-1-yl]-ethanol, 0.28 g (0.002 mol) of 6-hydroxy-nicotinic acid ethyl ester, 0.612 g of triphenylphosphine were added, 15 mL of anhydrous tetrahydrofuran was poured into the flask under condition of ice bath and nitrogen gas protection, then 0.35 mL of diethyl azodiformate (DEAD) dissolved in 5 mL of anhydrous tetrahydrofuran was added dropwise into the flask, after the dropwise addition, the temperature was elevated to room temperature, the agitation was kept overnight. The solvent was removed by evaporation using a rotation evaporator next day, the residue was poured into 100 mL of water, extracted for three times using total 150 mL of dichloromethane, the extract solutions were combined together, dried over anhydrous Na2SO4, concentrated, and separated by column chromatograph (eluent, petroleum ether:ethyl acetate:methanol=10:5:0.15) to obtain 0.32 g of 4-{2-[4-(3,6-dichloro-pyridazin-4-yl)-piperazin-1-yl]ethoxy}-phenylacetic acid methyl ester, a white solid. Yield: 42.3%, m.p. 140˜141° C. 1H-NMR(400 MHz, CDCl3) δppm: 1.37˜1.41(t, 3H, J=7.3 Hz), 2.79(brs, 4H), 2.91(brs, 2H), 3.36(brs, 4H), 4.35˜4.40(q, 2H, J=7.3 Hz), 4.57(brs, 2H), 6.78˜6.80(d, 2H, J=8.7 Hz), 6.86(s, 1H), 8.16˜8.18(dd, 1H, J1=8.7 Hz, J2=2.2 Hz).
