[Br:1][C:2]1[CH:3]=[CH:4][C:5]2[O:9][CH:8]([C:10]([O:12][CH2:13][CH3:14])=[O:11])[C:7](=[O:15])[C:6]=2[CH:16]=1.[N+:17]([C:20]1[C:25](F)=[CH:24][CH:23]=[CH:22][N:21]=1)([O-:19])=[O:18].C(=O)([O-])[O-].[K+].[K+]>CS(C)=O>[Br:1][C:2]1[CH:3]=[CH:4][C:5]2[O:9][C:8]([C:25]3[C:20]([N+:17]([O-:19])=[O:18])=[N:21][CH:22]=[CH:23][CH:24]=3)([C:10]([O:12][CH2:13][CH3:14])=[O:11])[C:7](=[O:15])[C:6]=2[CH:16]=1A mixture of ethyl 5-bromo-3-oxo-2,3-dihydro-1-benzofuran-2-carboxylate (1.42 g, 5.0 mmol), 2-nitro-3-fluoropyridine (0.71 g, 5 mmol) and potassium carbonate (0.83 g, 6.0 mmol) in DMSO (15 mL) is heated at 85-90° C. for 18 h. The mixture is cooled to ambient temperature and partitioned between EtOAc and brine. The layers are separated and the aqueous layer is further extracted with EtOAc. The combined organic extracts are dried (Na2SO4), filtered and concentrated in vacuo. The residue is purified by silica gel chromatography (gradient elution with hexanes-EtOAc) to afford the title compound.
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