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

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Reaction Steps

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).

Provenance & Evidence