Ethyl 2-(4,5-dibromo-6-oxopyridazin-1(6H)-yl)acetate (500 mg, 1.47 mmol) and 3-ethoxy-4-methoxybenzylamine (960 mg, 4.41 mmol) in 1,4-dioxane-water (1:1, 5 mL) were stirred with triethylamine (0.615 mL) at 100° C. for 2.5 hours. After cooling, ethyl acetate was added, and the organic layer was washed with saturated aqueous ammonium chloride and saturated aqueous sodium chloride and dried over anhydrous magnesium sulfate, and the solvent was removed by distillation. The resulting residue was purified by silica gel chromatography (chloroform/2-propanol=20/1) to give the desired product (640 mg, 98% yield).
