1-Benzyl-3-chloro-5-methoxypyridazin-4(1H)-one (13.6 g), 1-phenyl-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-pyrazole (22.0 g), potassium carbonate (51.0 g) and bis(di-tert-butyl(4-dimethylaminophenyl)phosphine)dichloropalladium(II) (1.92 g) were suspended in toluene (330 mL) and water (33.0 mL), and the suspension was heated under reflux under a nitrogen atmosphere for 24 hr. The reaction mixture was allowed to be cooled to room temperature, diluted with water and saturated aqueous sodium hydrogen carbonate solution, and the mixture was extracted with ethyl acetate. The extract was dried over anhydrous sodium sulfate, filtered, and concentrated. The residue was recrystallized from ethyl acetate/hexane to give the title compound (15.1 g).
