[OH:1][C:2]1[CH:9]=[CH:8][C:5]([CH:6]=[O:7])=[CH:4][CH:3]=1.C([O-])([O-])=O.[K+].[K+].Br[C:17]([CH3:24])([CH3:23])[C:18]([O:20][CH2:21][CH3:22])=[O:19].O>CC(C)=O>[CH2:21]([O:20][C:18](=[O:19])[C:17]([CH3:24])([O:1][C:2]1[CH:9]=[CH:8][C:5]([CH:6]=[O:7])=[CH:4][CH:3]=1)[CH3:23])[CH3:22]To 4-hydroxybenzaldehyde (20 g, 0.164 mol) in acetone (300 mL) was added K2CO3 (34 g, 1.5 equiv.) and the reaction was stirred at room temperature during 30 minutes. Ethyl 2-bromo-2-methylpropionate (36.2 mL, 1.5 equiv.) was added dropwise and the mixture was heated under reflux during 3 hours. K2CO3 (34 g, 1.5 equiv.) and ethyl 2-bromo-2-methylpropionate (36.2 mL, 1.5 equiv.) were added and the mixture was heated under reflux during 16 hours and then pourred into water and extracted with CH2Cl2 (3×300 mL). The combined organic layers were dried over Na2SO4, filtered and the solvent evaporated to afford crude intermediate. After chromatography on silicagel, eluting with cyclohexane/CH2Cl2 (6/4, then 8/2) and then with CH2Cl2, the titled compound was obtained as an oil (27 g, 69.85%)
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