Literature methods for preparing 5,6-dialkyl and 5,6-alkyl-arylpyridine-2,3-dicarboxylic acids and esters are limited and often require oxidation of alkyl or aryl substituents at positions 2 and 3 in order to obtain diacids. Recently there has been disclosed a method for the preparation of substituted and disubstituted pyridine-2,3-dicarboxylic acid esters and 2-alkyl nicotinates utilizing .alpha.-halo-.beta.-ketoesters and .alpha.,.beta.-unsaturated aldehydes or ketones in the presence of an ammonium salt. The use of .alpha.-halo-.beta.-ketoesters is not desired due to the fact that such materials are usually costly and unstable.
USPTO Backgrounds
USPTO Backgrounds