Iodine → 8-fluoro-3-nitro-2H-chromene-5-carboxylic acid methyl ester

Participants

Reaction Conditions

Reaction Steps

Into a reactor, equipped with mechanic stirrer and reflux condenser, 8-fluoro-2H-chromene-5-carboxylic acid methyl ester (6.6 g; 30 mmoles), sodium nitrite (6.2 g; 90 mmoles) and ethyl acetate (60 ml) were added at room temperature and under inert gas. The mixture was heated under stirring at 50° C., then iodine (2:6 g; 10 mmoles) and, slowly in 4 hours, Oxistrong 15® (7.4 ml) were added. At the end of the addition the reaction mixture was kept under stirring for a further hour, then cooled at 0° C. A 20% solution of sodium metabisulphite (about 25 ml) was added and the mixture was kept under stirring for 1 hour. After filtration the solid was washed with water (2×10 ml). The mother liquors were separated and, the previously filtered solid was added to the organic phase. The solvent was removed under reduced pressure and the semisolid residue was taken up with methanol (about 10 ml) and kept under stirring at 0° C. for 1 hour. After filtration and wash of the panel with methanol pre-cooled at 0° C. (3 ml), the resultant solid was dried in oven under vacuum at 40° C. overnight obtaining 8-fluoro-3-nitro-2H-chromene-5-carboxylic acid methyl ester (4.6 g; titre 92%; 55% yield). The mother liquors were evaporated to dryness obtaining an oil (2.7 g) containing 55% of 8-fluoro-3-nitro-2H-chromene-5-arboxylic acid methyl ester. Overall yield 75%.

Provenance & Evidence