A solution of 2,3-dichloro-5-methyl-1H-pyrrolo[2,3-d]pyridazin-4(5H)-one (404 mg) in DMF (70 ml) was dripped into a suspension of 60% sodium hydride-oil (96 mg) in DMF (10 ml) on an ice-water bath. After 3 hours of stirring at room temperature, a solution of 4-(4-chlorobenzoyl)benzyl bromide (681 mg) in DMF (15 ml) was added and the mixture was further stirred at room temperature for 18 hours. The reaction was stopped by adding water and the reaction mixture was extracted with ethyl acetate. The extract was dried over anhydrous magnesium sulfate and the solvent was distilled off under reduced pressure. The residue was then purified by silica gel column chromatography (developer; n-hexane: ethyl acetate=2:1→1:1) to provide the title compound as white powder (351 mg, yield 39%). 1H-NMR (DMSO-d6) δ: 3.68(3H,s), 5.73(2H,s), 7.30(2H,d,J=8.6Hz), 7.61(2H,d,J=8.6Hz), 7.72(2H,d,J=8.6Hz), 7.73(2H,d,J=8.6Hz), 8.71(1H,s).
