Pericyclic
Pericyclic reaction processes involve concerted bond reorganisation via a cyclic array of participating atomic centres. Pericyclic reactions can be subdivided into 2 + 4 Diels-Alder and other types of cycloaddition, electrocyclisation, cheletropic reactions, ene reactions, sigmatropic rearrangements, etc.

For more information look in the Chemogenesis webbook section on pericyclic reaction chemistry.