[CH2:1]([O:3][C:4](=[O:9])[CH:5]=[C:6]([O-:8])[CH3:7])[CH3:2].[Na+].Br[CH2:12][C:13](=[O:18])[C:14]([CH3:17])([CH3:16])[CH3:15].C(OCC)(=O)C.O>CN(C)C=O>[C:6]([CH:5]([CH2:12][C:13](=[O:18])[C:14]([CH3:17])([CH3:16])[CH3:15])[C:4]([O:3][CH2:1][CH3:2])=[O:9])(=[O:8])[CH3:7]To a solution of sodium 4-ethoxy-4-oxobut-2-en-2-olate (1.50 g) in N,N-dimethylformamide (50 mL) was added 1-bromo-3,3-dimethylbutan-2-one (2.0 mL), and the mixture was stirred at room temperature for 1 hr. Ethyl acetate and water were added to the reaction mixture, and the mixture was extracted with ethyl acetate. The organic layer was washed with saturated brine and dried over anhydrous magnesium sulfate. The solvent was evaporated and the residue was purified by silica gel column chromatography to give the title compound as a pale-yellow viscous substance (1.51 g, 53%).
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