[C:1]([O:7][CH3:8])(=[O:6])[CH2:2][C:3]([CH3:5])=[O:4].[Cl:9][C:10]1[CH:17]=[C:16]([Cl:18])[CH:15]=[CH:14][C:11]=1[CH:12]=O.CC(O)=O.CNC>CC(O)C>[Cl:9][C:10]1[CH:17]=[C:16]([Cl:18])[CH:15]=[CH:14][C:11]=1[CH:12]=[C:2]([C:3](=[O:4])[CH3:5])[C:1]([O:7][CH3:8])=[O:6]To a stirred solution of methyl acetoacetate (345 mg, 2.97 mmol) and 2,4-dichlorobenzaldehyde (500 mg, 2.86 mmol) in 2-propanol (5 mL) was added AcOH (7 mg, 0.11 mmol) and dimethylamine (0.06 mL, 2M in THF, 0.11 mmol). The reaction was heated to 40° C. for 4 hrs followed by cooling to ambient temperature for 15 hrs. The reaction was concentrated and purified by flash chromatography (silica gel, 30% EtOAc/hexane) to give methyl 2-(2,4-dichlorobenzylidene)-3-oxobutanoate as a mixture of two isomers (colorless oil, 610 mg, 78%).
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