反应详情

Concentrated H2SO4 (75 ml) was carefully added to 3-fluoropyridine N-oxide (Preparation 5) (50 g, 0.44 mol), cooled at room temperature by using a water bath. Fuming nitric acid (55 ml) was dissolved in concentrated sulfuric acid (75 ml) and the colourless solution was added drop-wise to the substrate over 15 minutes at room temperature. The yellow mixture was heated for 1.5 hours at 90° C. The mixture was allowed to reach room temperature and slowly poured onto ice (900 g). The aqueous layer was extracted with dichloromethane (3×500 ml) and the solvent evaporated under reduced pressure to yield a yellow solid. This was washed with pentane (200 ml). The residue was dissolved in dichloromethane (50 ml). A yellow precipitate formed which was filtered off to yield the title compound (10 g).

1. additionthe colourless solution was added drop-wise to the substrate over 15 minutes at room temperature
2. temperatureThe yellow mixture was heated for 1.5 hours at 90° C
3. customto reach room temperature
4. additionslowly poured onto ice (900 g)
5. extractionThe aqueous layer was extracted with dichloromethane (3×500 ml)
6. customthe solvent evaporated under reduced pressure
7. customto yield a yellow solid
8. washThis was washed with pentane (200 ml)
9. dissolutionThe residue was dissolved in dichloromethane (50 ml)
10. customA yellow precipitate formed which
11. filtrationwas filtered off