(2-Cyclopropyl-5-ethoxy-2'-fluorobiphenyl-4-yl)methanol → 2-Cyclopropyl-5-ethoxy-2'-fluorobiphenyl-4-carbaldehyde

Manganese dioxide (1.61 g) was added to a toluene (10 mL) solution of (2-cyclopropyl-5-ethoxy-2′-fluorobiphenyl-4-yl)methanol (1.06 g), and the mixture was stirred at 60° C. for 1 hour. Manganese dioxide (0.965 g) was further added to the reaction mixture, and the mixture was stirred at 60° C. for 30 minutes. 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 (955 mg).