Ethyl 4,5-dihydroxyquinoline-3-carboxylate → 4,5-Dihydroxyquinoline-3-carboxylic acid

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Reaction Steps

A mixture of 5-hydroxy-4-oxo-1,4-dihydro-quinoline-3-carboxylic acid ethyl ester (700 mg, 3 mmol) in 10% NaOH (20 ml) was heated at reflux overnight. After cooling, the mixture was extracted with ether. The aqueous phase was separated and acidified with conc. HCl to pH 1-2. The resulting precipitate was collected via filtration to give 5-hydroxy-4-oxo-1,4-dihydro-quinoline-3-carboxylic acid (A-3) (540 mg, 87%). 1H NMR (DMSO-d6) δ 13.7 (br, 1 H), 13.5 (br, 1 H), 12.6 (s, 1 H), 8.82 (s, 1 H), 7.68 (t,J=8.1 Hz, 1 H), 7.18 (d,J=8.4 Hz, 1 H), 6.82 (d, J=8.4 Hz, 1 H); ESI-MS 205.9 m/z (MH+).

Provenance & Evidence