2-Cyclopropyl-methyl-6-(3-fluoro-4-methoxyphenyl)-4-hydroxymethyl-2H-pyridazin-3-one (185 mg, 0.61 mmol), carbon tetrabromide (404 mg, 1.2 mmol) and pyridine (48 mg, 0.61 mmol) were dissolved in tetrahydrofuran (3 mL), and under ice-cold stirring, a solution of triphenylphosphine (319 mg, 1.2 mmol) in tetrahydrofuran (3 mL) was added. Under ice cooling, the mixture was stirred for 1 hour, and further stirred overnight at room temperature. Insoluble materials were filtered off, the solvent was distilled off under reduced pressure, and the residue was isolated and purified by column chromatography on silica gel (hexane/ethyl acetate=2/1) to yield the title compound as a yellow powder (yield: 155 mg, 69.5%).
