CYCLOADDITION REACTIONS OF HEPTAFULVENES - AN OVERVIEW

Heptafulvenes exhibit multiple reaction profiles in cycloaddition reac tions. 8-Alkyl and 8-alkoxy heptafulvenes are shown to be excellent 8 pi partners with electron deficient dienophiles. Heptafulvene chromium carbonyl complex undergoes [6+4] addition with butadiene. The [4+2] c ycloaddition reactions of heptafulvenes yield complex bicycle systems. Isolated examples of heptafulvene participating as a 2 pi addend are also reported Cyclohepta[b]furan-2-one, a tethered heptafulvene derive d from tropolone, undergoes both [8+2] and [4+2] additions.