Water → 5-Methoxy-4-oxo-4H-pyran-2-carboxylic acid

In a 250 ml round-bottom flask, 2-hydroxymethyl-5-methoxy-4-pyranone (2.2 g, 1 equiv.) was dissolved in 85 ml of methanol and 19.6 g of active manganese dioxide were added (16 equiv.). The reaction mixture was heated under reflux for 1.5 h, then cooled to room temperature. The insoluble part was filtered out and the remaining filtrate solution was concentrated to ca. a third of the initial volume. To this, 30 ml of water, 10 ml of NaOH 1 N and 3.3 g of silver oxide (1 equiv.) were added. The resulting mixture was reacted for 1 h at room temperature and was then filtered over a celite pad to eliminate salts. The filtrate was concentrated under reduced pressure to remove methanol therefrom and then washed with dichloromethane. Subsequently HCl 2 N (12 ml) was added to the water-soluble phase to form a precipitate which was collected by filtration, washed with diethyl ether and dried under vacuum at 50° C. 5-Methoxy-4-oxo-4H-pyran-2-carboxylic acid was obtained as a white solid (1.2 g, 50% yield).

1. temperatureThe reaction mixture was heated
2. temperatureunder reflux for 1.5 h
3. filtrationThe insoluble part was filtered out
4. concentrationthe remaining filtrate solution was concentrated
5. customThe resulting mixture was reacted for 1 h at room temperature
6. filtrationwas then filtered over a celite pad
7. concentrationThe filtrate was concentrated under reduced pressure
8. customto remove methanol
9. washwashed with dichloromethane
10. additionSubsequently HCl 2 N (12 ml) was added to the water-soluble phase
11. customto form a precipitate which
12. filtrationwas collected by filtration
13. washwashed with diethyl ether
14. customdried under vacuum at 50° C

ORD record

ord-d385313217434693908a6f801418a67e

Source dataset

uspto-grants-2015_08

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US09101613B2