C([Li])CCC.Br[C:7]1[CH:12]=[CH:11][C:10]([CH:13]([O:16]C)OC)=[CH:9][CH:8]=1.[C:18]1(=O)[CH2:22][CH2:21][CH2:20][CH2:19]1.FC(F)(F)C(O)=O>C1COCC1.C(OCC)(=O)C.ClCCl.O>[C:18]1([C:7]2[CH:8]=[CH:9][C:10]([CH:13]=[O:16])=[CH:11][CH:12]=2)[CH2:22][CH2:21][CH2:20][CH:19]=1
n-Butyllithium (7.2 mL, 1.56 M hexane solution, 11.2 mmol) was added to a solution in THF (25 mL) of 1-bromo-4-(dimethoxymethyl)benzene (2.29 g, 9.91 mmol) at −78° C. The mixture was stirred at the same temperature for 2 hours, and then cyclopentanone (1.34 mL, 15.1 mmol) was added thereto. The resulting mixture was heated to room temperature and then stirred for 1 hour. The reaction was terminated by adding a saturated ammonium chloride aqueous solution, and an extraction with ethyl acetate was conducted three times. The resulting organic layers were washed with water and saturated brine and then dried over anhydrous magnesium sulfate. The solvent was evaporated, and the resulting residue was purified by silica gel column chromatography (hexane:ethyl acetate, 5:1, v/v) to give an oily compound. Trifluoroacetic acid (9 mL) was added to a dichloromethane-water (9.1 mL, 100:1, v/v) mixture solution containing the resulting oily compound at room temperature, and the mixture was continuously stirred for 20 minutes. The solvent was evaporated, and the resulting residue was purified by silica gel column chromatography (hexane:ethyl acetate, 10:1, v/v) to give 1.18 g of the title compound (light brown crystalline solid, yield: 90%).
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