C[O-].[Na+].[CH2:4]([O:6][C:7](=[O:17])[C:8](CC)(CC)P(O)(O)=O)C.[CH2:18](/[C:20](=[CH:23]\[CH2:24][CH3:25])/[CH:21]=O)[CH3:19].O>CO>[CH2:18](/[C:20](=[CH:23]\[CH2:24][CH3:25])/[CH:21]=[CH:8]/[C:7]([O:6][CH3:4])=[O:17])[CH3:19]To a 28 wt % solution of sodium methoxide in methanol (25.7 g) at 10° C. were added dropwise diethyl phosphonoacetic acid ethyl ester (25.3 g) and (E)-2-ethyl-2-pentenal (11.5 g) successively under a nitrogen atmosphere. The reaction mixture was stirred at room temperature for 3 hours, poured into chilled water and extracted with ethyl acetate. The extract was washed with brine, dried over anhydrous magnesium sulfate, and evaporated in vacuo. The residue was chromatographed on silica gel (dichloromethane) to give 13.4 g of methyl (E,E)-4-ethyl-2,4-heptadienoate as an oil.
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