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

Temperature

50 °C

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%.

1. customInto a reactor, equipped with mechanic stirrer
2. temperaturereflux condenser
3. temperatureThe mixture was heated
4. additionOxistrong 15® (7.4 ml) were added
5. additionAt the end of the addition the reaction mixture
6. stirringunder stirring for a further hour
7. temperaturecooled at 0° C
8. stirringunder stirring for 1 hour
9. filtrationAfter filtration the solid
10. washwas washed with water (2×10 ml)
11. customThe mother liquors were separated
12. additionthe previously filtered solid was added to the organic phase
13. customThe solvent was removed under reduced pressure
14. stirringunder stirring at 0° C. for 1 hour
15. filtrationAfter filtration
16. washwash of the panel with methanol
17. temperaturepre-cooled at 0° C. (3 ml)
18. customthe resultant solid was dried in oven under vacuum at 40° C. overnight

ORD record

ord-7c6c1feaf00c468a873a1f3956aeebc6

Source dataset

uspto-grants-2007_09

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US07265251B2