text: The most well-known example of a coarctate transition state is that of the epoxidation of an olefin by dimethyldioxirane.  In this transition state, the oxygen atom transferred to the olefin forms a cycle with the acetone leaving group and a cycle with the olefin undergoing epoxidation.  Another well-studied reaction is the fragmentation of spirocyclic ozonides into formaldehyde, CO, and an olefin.
  Selection rules, resembling the Woodward-Hoffmann rules, have been proposed to explain patterns in reaction activation energy related to transition state topology or orbital symmetry.