Etude par RMN et uv de la protonation des enamines cationiques

Enamines, substituted on β carbon by a pyrylium cation have a mesomeric structure close to pyrannylidene—immonium. Conjugation between pyrylium nucleus and the double bond influences the relative stability of the C- and N- protonated compounds. This conjugation stabilizes the N-protonated compounds which are in equilibrium with the less conjugated C-protonated. In the same conditions, aliphatic enamines do not comprise such an equilibrium. The positions of the studied equilibria depend partly on the substituents of the β carbon and of the protonating reactant.