[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+].II.C(OCC)(=O)C>O>[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 (120 g;0.609 moles), sodium nitrite (96.6 g; 1.4 moles), iodine (31.2 g; 0.123 moles) and ethyl acetate (720 ml) were charged at room temperature and under inert gas. The mixture was heated under stirring at 40° C., then Oxistrong 15® (173.4 g) was added in 4 hours. At the end of the addition the reaction mixture was kept under stirring for 1 hour, then cooled at 20° C. Water (480 ml) was added and the mixture was kept under stirring for 1 hour. After filtration and wash of the panel with isopropyl acetate pre-cooled at 0° C. (2×120 ml) and then with water (150 ml), the solid was dried in oven under vacuum at 50° C. overnight obtaining 8-fluoro-3-nitro-2H-chromene-5-carboxylic acid amide (112.7 g; titre 91%; 70% yield).
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