Electrocyclic Reactions and Related Rearrangements

In their now classic monograph [1], Wooodward and Hoffmann concentrate on three basic types of “no mechanism” reaction: Electrocyclic reactions — notably polyene cyclizations, cycloadditions, and sigmatropic rearrangements. These three reaction types will be taken up in this and the next two chapters from the viewpoint of Orbital Correspondence Analysis in Maximum Symmetry (OCAMS) [2, 3, 4], the formalism of which follows naturally from that developed in Chapter 4. The similarities to the original WH-LHA approach [5, 6], and the points at which OCAMS departs from it, will be illustrated. In addition, a few related concepts, such as “ allowedness” and “forbiddenness”, global vs. local symmetry, and “concertedness” and “synchronicity”, will be taken up where appropriate.