https://doi.org/10.1351/goldbook.P04932
A enol prototropy of pentane-2,4-dione (acetylacetone).
Because the - and -atomic orbitals that interchange roles are orthogonal, such a reaction does not proceed through a fully
concerted transformation
is pseudopericyclic if the primary changes in bonding occur within a cyclic array of atoms at one (or more) of which nonbonding and bonding atomic orbitals interchange roles. A formal example is the enol ![Not defined](/img/inline/P04932.png)
conjugated transition state
and is thus not a pericyclic reaction
and therefore not governed by the rules that express orbital symmetry
restrictions applicable to pericyclic reactions.