[Mg].Br[C:3]1[CH:8]=[CH:7][CH:6]=[C:5]([F:9])[CH:4]=1.[Br-].[Li+].[F:12][C:13]1[CH:14]=[C:15]([Mg]Br)[CH:16]=[CH:17][CH:18]=1.[C:21](Cl)(=[O:25])[C:22](Cl)=[O:23]>C1COCC1.[Cu]Br>[F:9][C:5]1[CH:4]=[C:3]([C:22]([C:21]([C:15]2[CH:16]=[CH:17][CH:18]=[C:13]([F:12])[CH:14]=2)=[O:25])=[O:23])[CH:8]=[CH:7][CH:6]=1To anhydrous THF (80 mL) is added magnesium (2.9 g, 0.120 mol) and 1-bromo-3-fluorobenzene (12.76 g, 0.114 mol) in anhydrous THF (30 mL). The mixture is stirred at 21° C. for 1.5 h. To THF (60 mL) is added lithium bromide (13.22 g, 0.015 mol) and copper (I) bromide (10.9 g, 0.0762 mol) and the mixture is stirred at RT until homogenous, then cooled to 0° C. To this solution is added 3-fluorophenylmagnesium bromide solution followed by a solution of oxalyl chloride (2.76 mL, 0.0317 mol) in THF (20 mL). The solution is stirred at 0° C. for 15 min, then quenched by ammonium chloride solution, and extracted with EtOAc. The organic solution is dried (Na2SO4), filtered, and the filtrate rotary evaporated. The residue is purified by filtration through silica gel; elution with heptane and heptane:EtOAc (9:1) gives 0.70 g of the product 20.
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