1-Butoxy-4-(4-(2,3-difluorophenyl)cyclohex-1-enyl)-2,3-difluorobenzene (s-20) (7.2 g) and THF (200 ml) were put in a reaction vessel under an atmosphere of nitrogen and cooled to −74° C. sec-Butyllithium (a 1.00 M solution in n-hexane and cyclohexane; 23.0 ml) was added dropwise thereto in the temperature range of −74° C. to −70° C., and the stirring was continued for another 2 hours. Then, trimethyl borate (2.0 g) in a THF (30 ml) solution was added dropwise thereto in the temperature range of −74° C. to −65° C., and the stirring was continued for another 8 hours while the mixture was allowed to come to 25° C. Then, the reaction mixture was poured into a vessel containing 1 N hydrochloric acid (100 ml) and ice-water (200 ml), and mixed with them. Ethyl acetate (200 ml) was added and the mixture was allowed to separate into organic and aqueous phases, and the extraction was carried out. The combined organic phase was washed successively with water, a saturated aqueous solution of sodium hydrogencarbonate and salt water, and dried over anhydrous magnesium sulfate. Then, the solvent was distilled off under reduced pressure. The residue and acetic acid (50 ml) were put in a reaction vessel under an atmosphere of nitrogen, and hydrogen peroxide (a 31% aqueous solution; 1.0 g) was added in the temperature range of 25° C. to 30° C., and then the stirring was continued for another 2 hours. Then, the reaction mixture was poured into a vessel containing an aqueous solution of sodium hydrogensulfite (100 ml) and ethyl acetate (200 ml), and mixed with them. The mixture was then allowed to stand until it had separated into organic and aqueous phases, and the extraction was carried out. The combined organic phase was washed successively with water and salt water, and dried over anhydrous magnesium sulfate. Then, the solvent was distilled off to give 1-butoxy-4-(4-(2,3-difluorophenyl)cyclohex-1-enyl)-2,3-difluorophenol (s-21) (5.9 g). The yield based on the compound (s-20) was 78.6%.
