[F:1][C:2]1[CH:9]=[C:8]([F:10])[CH:7]=[CH:6][C:3]=1[CH:4]=O.[C:11]([O:17][CH2:18][CH2:19][O:20][CH3:21])(=[O:16])[CH2:12][C:13]([CH3:15])=[O:14].N1CCCCC1.C(O)(=O)C>C(O)(C)C>[C:13]([C:12](=[CH:4][C:3]1[CH:6]=[CH:7][C:8]([F:10])=[CH:9][C:2]=1[F:1])[C:11]([O:17][CH2:18][CH2:19][O:20][CH3:21])=[O:16])(=[O:14])[CH3:15]5.0 g (35 mmol) of 2,4-difluorobenzaldehyde are dissolved in 100 ml of isopropanol with 5.7 g (35 mmol) of 2-methoxyethyl acetoacetate. A freshly prepared solution of 1.0 ml of piperidine and 0.5 ml of glacial acetic acid in 5 ml of isopropanol is added to this solution and it is stirred overnight at 40° C. The mixture is concentrated, the residue is taken up in toluene, the solution is concentrated again and the residue is purified by filtration on 100 ml of silica gel (eluent: toluene/ethyl acetate 100:1) to give 5 g of the target compound as a yellow oil which is immediately reacted further.
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