[F:1][C:2]1[C:11]2[O:10][CH2:9][CH:8]=[CH:7][C:6]=2[C:5]([C:12]([NH2:14])=[O:13])=[CH:4][CH:3]=1.[N:15]([O-:17])=[O:16].[Na+].[I-].[K+]>C(OCC)(=O)C>[F:1][C:2]1[C:11]2[O:10][CH2:9][C:8]([N+:15]([O-:17])=[O:16])=[CH:7][C:6]=2[C:5]([C:12]([NH2:14])=[O:13])=[CH:4][CH:3]=1Into a reactor, equipped with a mechanic stirrer and a reflux condenser, 8-fluoro-2H-chromene-5-carboxylic acid amide (2 g; 10 mmoles), sodium nitrite (1.4 g; 20 mmoles), potassium iodide (0.33 g; 2 mmoles) and ethyl acetate (20 ml) were charged at room temperature and under inert gas. The mixture was heated at 40° C., then Oxistrong 15® (4 ml) was added in 4 hours. At the end of the addition the reaction mixture was kept under stirring for 1.5 hours, then cooled at 20° C. and diluted with ethyl acetate up to complete dissolution (about 150 ml). After washing with a 20% sodium metabisulphite solution, the phases were separated. The organic phase was washed with a saturated sodium chloride solution, dried and the solvent was removed under reduced pressure, obtaining 8-fluoro-3-nitro-2H-chromene-5-carboxylic acid amide (1.8 g; titre 88%; 66% yield).
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