Etude de la reactivite de l'ion azoture vis á vis de cations heterocycliques-I: Inhibition de la formation d'azides covalents par un complexe pyrylium-azoture constituant un “cul de sac” reactionnel. mise en evidence expérimentale

The reactivity of azide anion with pyrylium and thiopyrylium substituted cations depends on the substitution of the heterocyclic cation. Only sterically hindered pyrylium or thiopyrylium cations lead to the formation of covalent azides. On the other hand, pyrylium or thiopyrylium cations which are not sterically hindered give a donor acceptor complex. The formation of this complex constitutes a dead-end reaction on the normal pathway to covalent azides. This apparently unusual behaviour cannot be rationalized with simple concepts such as charge density or frontier orbital coefficients.