反应详情

2-Hydroxypyridine or quinoline carboxylic acids and esters are useful as herbicide and pharmaceutical intermediates. One method for their preparation involves oxidizing quinolinic acid to obtain 2 3-bis(methoxycarbonyl)pyridine N-oxide, treating the N-oxide with acetic anhydride to give the 2-acetoxy compound, and hydrolyzing to give 6-hydroxy-2,3-dimethoxycarboxylpyridine in 27.5% overall yield; see E. Spinner et al., J. Chem. Soc. (B), 289 (1971). Another method involves reacting an ester of coumalic acid with ammonia to yield 2-hydroxy-5-pyridinecarboxylic acid; see W. T. Caldwell et al. J. Am. Chem. Soc. 66, 1479 (1944). Another method involves converting alpha-pyrone-6-carboxylic acid with ammonium acetate and glacial acetic acid into 2-pyridine-6-carboxylic acid; see J. Fried et al., J. Org. Chem. 6, 566 (1941).