(2-Cyclopropyl-4'-fluoro-5-isopropoxybiphenyl-4-yl)methanol → 2-Cyclopropyl-4'-fluoro-5-isopropoxybiphenyl-4-carbaldehyde

Manganese dioxide (16.6 g) was added to a toluene (80 mL) solution of (2-cyclopropyl-4′-fluoro-5-isopropoxybiphenyl-4-yl)methanol (5.75 g), and the mixture was stirred at 60° C. for 1 hour in a nitrogen atmosphere. The reaction mixture was filtered, and then, the solvent was distilled off under reduced pressure. The obtained residue was purified by silica gel column chromatography (hexane/ethyl acetate) to obtain the title compound (4.54 g).