CC(C)([O-])C.[K+].[CH3:7][C:8]1[CH:13]=[CH:12][C:11]([CH2:14][C:15]([O:17][C:18]([CH3:21])([CH3:20])[CH3:19])=[O:16])=[CH:10][CH:9]=1.Br[CH:23]([CH2:25][CH3:26])[CH3:24].O>CN(C=O)C.C(OCC)C>[CH3:24][CH:23]([CH2:25][CH3:26])[CH:14]([C:11]1[CH:10]=[CH:9][C:8]([CH3:7])=[CH:13][CH:12]=1)[C:15]([O:17][C:18]([CH3:21])([CH3:20])[CH3:19])=[O:16]Under argon, 19.58 g (174.5 mmol) of potassium tert-butoxide were initially charged in 200 ml of DMF, the mixture was cooled to 0° C., 30 g (145.4 mmol) of tert-butyl (4-methylphenyl)acetate, dissolved in 50 ml of DMF, were added slowly and the mixture was then stirred at 0° C. for 30 min. 18.95 ml (174.5 mmol) of 2-bromobutane were then slowly added drowise, and the solution was stirred at 0° C. for 4 h. 200 ml of water and 200 ml of diethyl ether were then added to the reaction solution. The aqueous phase was extracted twice with diethyl ether. The combined organic phases were dried over magnesium sulfate. After filtration, the solvent was removed under reduced pressure. The crude product was purified chromatographically on silica gel (mobile phase cyclohexane/ethyl acetate 20:1). This gave 15.5 g (59.1 mmol, 40.6% of theory) of a colorless liquid.
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