Generation and Reactions of an Octacyclic Hindered Pyramidalized Alkene

Octacyclo­[10.6.1.01,10.03,7.04,9.08,19.011,16.013,17]­nonadeca-5,8,14-triene
(27), a hindered pyramidalized alkene, has been generated
from a diiodide precursor. Contrary to the usual behavior of known
pyramidalized alkenes, no Diels–Alder adducts were obtained
from the present alkene when it was generated by different standard
procedures in the presence of different dienes. However, products
derived from the reduction, t-BuLi addition, condensation
with the solvent, or dimerization were isolated from these reactions,
depending on the conditions used to generate it. No [2 + 2] cross
product among this pyramidalized alkene and tricyclo­[3.3.1.03,7]­non-3­(7)-ene was formed when a mixture of the corresponding precursor
diiodides was reacted with sodium amalgam. The analysis of selected
geometrical and orbital parameters determined from quantum mechanical
calculations indicates that the degree of pyramidalization of this
alkene and its higher steric hindrance compared with other polycyclic
pyramidalized alkenes may explain its peculiar reactivity.