Water → 6-Fluoronicotinic Acid

Temperature

100 °C

A solution of the 2-fluoro-5-methylpyridine (30 g) in water (1.2 L) was stirred with a mechanical stirrer, potassium permanganate (100 g) was added in portions and the mixture heated to 100° C. When the characteristic purple color of the mixture faded to black, another portion of potassium permanganate (50 g) was added and the mixture was then stirred at 100° C. for 4.5 hours. The mixture was filtered hot, the filtrate was cooled and extracted with ether to remove unreacted starting material. The aqueous layer was neutralized to pH 7 with concentrated HCl and concentrated to a volume of 350 mL. The pH was lowered by addition of concentrated HCl to pH 4-2 at which point a large amount of precipitate appeared. The precipitate was filtered and the aqueous layer was extracted with ethyl acetate (500 mL). The organic layer was dried, evaporated, and the solids combined to give 2-fluoropyridine-5-carboxylic acid (17.1 g) as a colorless solid having a melting point of 275°-278° C.

1. filtrationThe mixture was filtered hot
2. temperaturethe filtrate was cooled
3. extractionextracted with ether
4. customto remove unreacted
5. concentrationconcentrated to a volume of 350 mL
6. additionThe pH was lowered by addition of concentrated HCl to pH 4-2 at which point a large amount of precipitate
7. filtrationThe precipitate was filtered
8. extractionthe aqueous layer was extracted with ethyl acetate (500 mL)
9. customThe organic layer was dried
10. customevaporated

ORD record

ord-1181398ed4e84b788fc6d6423860a5cc

Source dataset

uspto-grants-1996_12

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US05583148