CC(C)([O-])C.[K+].C(O)(C)(C)C.[CH2:12]([O:14][C:15](=[O:21])[CH2:16][C:17](=[O:20])[CH2:18][CH3:19])[CH3:13].Br[CH2:23][C:24]1[CH:29]=[CH:28][C:27]([Cl:30])=[CH:26][CH:25]=1>O1CCCC1.O>[CH2:12]([O:14][C:15](=[O:21])[CH:16]([CH2:23][C:24]1[CH:29]=[CH:28][C:27]([Cl:30])=[CH:26][CH:25]=1)[C:17](=[O:20])[CH2:18][CH3:19])[CH3:13]A suspension of potassium tert-butoxide (7.8 g) in anhydrous tetrahydrofuran (140 mL) at 0° C. was treated with a mixture of tert-butanol (0.3 mL) and 3-oxopentanoic acid ethyl ester (10 g). After stirring at room temperature for 30 minutes a solution of 1-bromomethyl-4-chlorobenzene (14 g) in tetrahydrofuran (20 mL) was added and the resulting mixture stirred at room temperature for 6 days. The mixture was diluted with water, extracted with ethyl acetate and the combined extracts washed with water and saturated aqueous sodium chloride solution and then dried over magnesium sulfate. The solvent was removed under reduced pressure and the residue purified by column chromatography on silica gel, eluting with a mixture of pentane and ethyl acetate (1:0 to 10:1 by volume) to afford title compound as a yellow oil, 9.3 g.
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