Pyridine-2,3-dicarboxylic acids bearing an halogen in the position α or β to the nitrogen atom were synthesized by oxidation of the corresponding quinolines. Two methods, using either ozone followed by hydrogen peroxide or ruthenium tetroxide under catalytic conditions were used. Diacids 1b,c and 2a-c substituted in 6-position by a chlorine or bromine and in 5-position by a fluorine, chloride or bromine, respectively, were isolated in yields ranging from 46-71%. Yields of 6-fluoro and 6- or 5-iodo diacids 1a,d and 2d did not exceed 30%.
oxidation - quinolines - pyridine-2,3-dicarboxylic acids - halogens - ozonolysis - ruthenium tetroxide
