[CH2:1]([O:3][C:4](=[O:9])[CH2:5][C:6]([O-:8])=O)[CH3:2].[K+].[Cl-].[Mg+2].[Cl-].[F:14][C:15]1[CH:23]=[C:22]([O:24][CH3:25])[CH:21]=[CH:20][C:16]=1C(Cl)=O.Cl>C(#N)C.C(N(CC)CC)C>[F:14][C:15]1[CH:23]=[C:22]([O:24][CH3:25])[CH:21]=[CH:20][C:16]=1[C:6](=[O:8])[CH2:5][C:4]([O:3][CH2:1][CH3:2])=[O:9]To a solution of 12.34 g (72.5 mmol) of potassium 3-ethoxy-3-oxopropanoate in suspension in 150 ml anhydrous acetonitrile are added at −0° C. under argon 10.11 ml (72.5 mmol) of triethylamine and 8.28 g (87 mmol) of magnesium (II) chloride. The reaction mixture is stirred for 5 h at room temperature, then at 0° C. a solution of 5.47 g (29 mmol) of 2-fluoro-4-methoxybenzoyl chloride dissolved in 30 ml of acetonitrile is added as well as 4.45 ml (31.9 mmol) of triethylamine. The reaction mixture is stirred for 18 h at room temperature then a 1M hydrochloric acid solution is added until the suspension disappears. The product is extracted several times with ethyl acetate. The organic phases are combined, dried over magnesium sulfate, and concentrated. The residue is purified by chromatography on silica (cyclohexane/ethyl acetate eluent: 85:15) to yield 5.46 g (78%) of ethyl 3-(2-fluoro-4-methoxyphenyl)-3-oxopropanoate in the form of a yellow oil which crystallizes over time.
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