[C:1]([O:7][CH3:8])(=[O:6])[C:2]([O:4]C)=O.[F:9][C:10]1[CH:15]=[CH:14][C:13]([C:16](=[O:18])[CH3:17])=[CH:12][CH:11]=1.C[O-].[Na+].Cl>CO>[F:9][C:10]1[CH:15]=[CH:14][C:13]([C:16](=[O:18])[CH2:17][C:2](=[O:4])[C:1]([O:7][CH3:8])=[O:6])=[CH:12][CH:11]=1Dimethyl oxalate (18.80 g, 0.159 mol) and 4'-fluoroacetophenone (20.0 g, 0.145 mol) were charged to a 1000 mL round-bottom flask and diluted with methanol (400 mL). The reaction flask was placed in a sonication bath (Bransonic 1200), and sodium methoxide (25% in methanol, 70 mL) was added over 25 minutes. The reaction was sonicated at 45° C. for 16 hours. The reaction became an insoluble mass during this time. The solid was mechanically broken up, then poured into a hydrochloric acid solution (1N, 500 mL). A magnetic stirrer was added, and the white suspension was stirred vigorously at room temperature for 60 minutes. The suspension was cooled to 0° C. and held for 30 minutes. The solid was filtered, and the filter cake was then washed with cold water (100 mL). Upon drying, methyl 4-[4-fluorophenyl]-2,4-diketobutanoate was obtained (22.91 g, 70.6%) as the enol: 1H NMR (CDCl3 /300 MHz) 8.03 (ddd, J=8.86 Hz, J=8.66 Hz, J=5.03 Hz, 2H), 7.19 (dd, J=8.86 Hz, J=8.66 Hz, 2H), 7.04 (s, 1H), 3.95(s, 3H). 19F NMR (CDCl3 /282.2 MHz) -103.9(m).
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