The Valence Tautomerism of Cyclooctatetraene

Abstract
The Diels‐Alder adducts of cyclooctatetraene and its derivatives are derived from the bicyclo[4,2,0]octane structure. A kinetic investigation shows that the Diels‐Alder addition of dienophiles to cyclooctatetraene and phenylcyclooctatetraene is preceded by a valence tautomerism equilibrium with bicyclo[4,2,0]octa‐2,4,7‐triene or its 7‐phenyl derivative.