Synthesis of 5-carboxy-6-methyl-3,4-dihydro-2(1H)-pyridone derivatives and their electrochemical oxidation to 2-pyridones

⿢A series of new 3,4-dihydropyridones were synthesized..⿢A new tricyclic heterocycle formed when o-salicylaldehyde was used in the reaction.⿢The X-ray crystallographic image indicates that the tricyclic heterocycle crystallizes as hydrogen bonded chains with its antipode.⿢3,4-Dihydropyridones undergo an irreversible oxidation at potential ⿥1.5 V vs NHE with the loss of 2 electrons and 2 protons to form 2-pyridones.⿢2-Pyridone structure is proved by single crystal X-ray crystallography, indicating that it crystallizes as an NHO hydrogen bonded dimer.