Under argon atmosphere, to a solution of 4-trifluoromethoxybromobenzene (10.0 g) in tetrahydrofuran (75 ml) was dropwise added n-butyllithium (1.6M, hexane solution) (28.5 ml) at −78° C. for 20 minutes, and the mixture was stirred for 40 minutes. To the reaction mixture was dropwise added a solution of trimethyl borate (12.9 g) in tetrahydrofuran (12 ml) for 15 minutes, and the mixture was stirred at −78° C. for 30 minutes and at room temperature for 1 hour. To the reaction mixture was added was dropwise added 10% sulfuric acid (57.6 ml) for 15 minutes, and the mixture was stirred for 2 hours, extracted with ethyl acetate, washed with saturated sodium chloride solution, dried with magnesium sulfate and concentrated under reduced pressure. The residue was crystallized from hexane to give 4-trifluoromethoxyphenyl borate (2.7 g) as colorless crystals. Under argon atmosphere, a solution of ethyl 7-bromo-2,3-dihydro-1-benzoxepine-4-carboxylate (500 mg), the above 4-trifluoromethoxyphenyl borate (380 mg) and potassium carbonate (0.46 g) in toluene-ethanol-water (20-2-2 ml) was stirred at room temperature for 1 hour. To the reaction mixture was added tetrakistriphenylphosphinepalladium (0.06 g), and the mixture was refluxed for 18 hours and cooled to room temperature. The organic layer was washed with saturated sodium chloride solution, dried with magnesium sulfate and concentrated under reduced pressure. The residue was separated and purified with column chromatography (ethyl acetate/hexane=1:10 ) to give ethyl 7-(4-trifluoromethoxyphenyl)-2,3-dihydro-1-benzoxepine-4-carboxylate (379 mg) as colorless crystals.
