Intramolecular 2h group-transfer in heterocyclic bridged-ring systems (dyotropic rearrangements)

Diarylnitrilimines, derived by thermolysis of appropriate diaryltetrazoles, form(4+2)π cyclo-adducts with dipolarophiles of the isodrin type, e.g. $\text{(1)}$; the resulting 2-pyrazolines thermally rearrange into pyrazoles by hydrogen group transfer. Kinetic data for examples of this and related reactions are reported.