Synthesis and structural characterisation of amides from picolinic acid and pyridine-2,6-dicarboxylic acid

AbstractCoupling picolinic acid (pyridine-2-carboxylic acid) and pyridine-2,6-dicarboxylic acid withN-alkylanilines affords a range of mono- and bis-amides in good to moderate yields. These amides are of interest for potential applications in catalysis, coordination chemistry and molecular devices. The reaction of picolinic acid with thionyl chloride to generate the acid chloridein situleads not only to theN-alkyl-N-phenylpicolinamides as expected but also the corresponding 4-chloro-N-alkyl-N-phenylpicolinamides in the one pot. The two products are readily separated by column chromatography. Chlorinated products are not observed from the corresponding reactions of pyridine-2,6-dicarboxylic acid. X-Ray crystal structures for six of these compounds are described. These structures reveal a general preference forcisamide geometry in which the aromatic groups (N-phenyl and pyridyl) arecisto each other and the pyridine nitrogenantito the carbonyl oxygen. Variable temperature1H NMR experiments provide a window on amide bond isomerisation in solution.