Dependence of the reactivity of five-membered aromatic heterocycles on their structure. 5. Protonation of furazane, furoxane, and their aminoderivatives

Proton affinity of furazane, furoxane, and their aminoderivatives for protonation at various centers was calculated by ab initio methods using the STO-3G basis set. Basicity was found to decrease in the following order: N-oxide oxygen atom, endocyclic nitrogen atom, amino group. The presence in the ring of aminogroups or N-oxide functions leads to elevated proton affinity of the basic centers which are located in the active positions of the ring.