General procedure for the synthesis of 5,6-dimethylpyridine-2-carboxylic acid from 5,6-dimethylpyridine-2-carbonitrile: 5,6-dimethylpyridine-2-carbonitrile (Example 91b) was subjected to concentrated hydrochloric acid (15 mL), and the reaction was carried out at reflux overnight. Upon completion of the reaction, the solvent was removed by evaporation and the solid residue obtained was co-evaporated with ethanol several times to remove the residual hydrochloric acid. Finally, drying gave 453 mg of 5,6-dimethylpyridine-2-carboxylic acid in 80% yield and the product was a white solid. Mass spectrometry analysis showed a molecular ion peak (M + H) of 152.1.
