To a round bottom flask was added 4,5-dichloropyridazin-3(2H)-one (50 g, 303.03 mmol), N,N-dimethylformamide (DMF, 150 mL), potassium carbonate (K2CO3, 46 g, 333.33 mmol) and benzyl bromide (51.83 g, 303.03 mmol). The reaction mixture was stirred at room temperature for 16 hours. Upon completion of the reaction, the reaction mixture was slowly poured into water (500 mL) and a solid precipitate was precipitated. The suspension was continued to be stirred at room temperature for 1 hour. Subsequently, the solid product was separated by filtration and dried under vacuum to afford 2-benzyl-4,5-dichloropyridazin-3(2H)-one as a tan solid (74 g, 97% yield). The product was analyzed by high performance liquid chromatography (HPLC, Method A) with a retention time of 2.788 min; liquid chromatography-mass spectrometry (LCMS) showed a molecular ion peak (M+1) of 255.1.
