THE MECHANISM OF THE HANTZSCH PYRIDINE SYNTHESIS: A STUDY BY 15N AND 13C NMR SPECTROSCOPY

Article abstract of DOI:10.1016/S0040-4020(01)88178-3

The mechanism of the reactions of ammonia and benzaldehyde with three different beta-dicarbonyl compounds to form the corresponding dihydropyridines has been followed by NMR.In each case the pathway is shown to involve the reaction of benzaldehyde with one molecule of beta-dicarbonyl to give chalcone, and of the ammonia with a second molecule of beta-dicarbonyl to give an enamine.The rate determing stage is shown to be the Michael addition of the chalcone to the enamine.