Cyclopentyl bromide (1.2 g, 8.1 mmol) was added to a solution of N-(2-fluoro-4-chloro-5-hydroxyphenyl)-3,4,5,6-tetrahydrophthalimide (2.0 g, 6.76 mmol) and potassium carbonate (0.60 g, 4.34 mmol) in acetonitrile (50 ml), followed by stirring for 2 hours under refluxing. After completion of the reaction, 1N hydrochloric acid (20 ml) was added to the resulting reaction mixture, and the mixture was extracted with ethyl acetate (20 ml×3 times). The organic layer was washed with water, dried over anhydrous magnesium sulfate, and the solvent was distilled off under reduced pressure. Ethanol (5 ml) was added to the resulting pale yellow oily substance, and the precipitated N-(2-fluoro-4-chloro-5-cyclopentyloxyphenyl)-3,4,5,6-tetrahydrophthalimide as a white solid (0.75 g, 2.06 mmol, 30.5% yield) was isolated by filtration. Spectral data and the like are as shown in Example 1.
