[H-].[Na+].[CH:3]1([C:9]([OH:11])=[O:10])[CH2:8][CH2:7][CH2:6][CH2:5][CH2:4]1.C([NH-])(C)C.[Li+].Br[CH2:18][CH:19]([CH2:22][CH3:23])[CH2:20][CH3:21].Cl>O1CCCC1.O.C1CCCCC1>[CH2:20]([CH:19]([CH2:22][CH3:23])[CH2:18][C:3]1([C:9]([OH:11])=[O:10])[CH2:8][CH2:7][CH2:6][CH2:5][CH2:4]1)[CH3:21]A suspension of 60% sodium hydride (980 mg) in tetrahydrofuran (80 ml) was stirred at room temperature and a tetrahydrofuran solution (10 ml) containing cyclohexanecarboxylic acid (3.00 g) was added dropwise thereto. After completion of addition, a mixture was stirred for 1 hour and cooled to 0° C., followed by adding a cyclohexane solution (18.7 ml) containing 1.5 M lithium isopropylamide dropwise thereto. Then, after stirring at room temperature for 1.5 hours and cooling to 0° C., a tetrahydrofuran solution (10 ml) containing 1-bromo-2-ethylbutane (4.64 g) was added dropwise thereto. The solution was gradually warmed to room temperature and stirred overnight. Water and a 10% hydrochloride solution were added to this reaction solution and the solution was extracted with ethyl acetate. The organic layer was washed with saturated brine and dried over anhydrous sodium sulfate. After drying, the resulting solution was concentrated to obtain 1-(2-ethylbutyl)cyclohexanecarboxylic acid (3.17 g, yield: 64%).
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