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