[Cl:1][C:2]1[CH:7]=[C:6]([F:8])[CH:5]=[CH:4][C:3]=1[F:9].[N+:10]([O-])([O-:12])=[O:11].[K+]>OS(O)(=O)=O>[Cl:1][C:2]1[CH:7]=[C:6]([F:8])[C:5]([N+:10]([O-:12])=[O:11])=[CH:4][C:3]=1[F:9]To a stirred solution of 1-chloro-2,5-difluorobenzene (0.770 g, 5.18 mmol) in concd H2SO4 (8.0 mL) at 0° C., KNO3.(0.525 g, 5.19 mmol) was added in one lot. The resulting yellow solution was allowed to warm to room temperature and stirred overnight at room temperature. It was then poured into ice (80 g) and extracted with ethyl acetate (75 mL). The ethyl acetate was dried over anhydrous Na2SO4, removed under vacuum and the residue was dried further under vacuum to afford 0.845 g (85%) of title compound as a yellow liquid; 1H NMR (CDCl3) δ 7.43 (dd, 1H, J1=9.6 Hz, J2=6.0 Hz), 7.93 (t, 1H, J=7.2 Hz).
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