Rigid polycyclic systems. The reaction between cyclopentadiene and acenaphthylene and spectral properties of the adducts and derived alcohols and ketones

The reaction between acenaphthylene and cyclopentadiene under kinetically controlled conditions gives endo- and exo-adducts in the ratio 3:1. The n.m.r., u.v., and i.r. spectra of the adducts and the alcohols and ketones derived from them are compared with those of the corresponding compounds formed from the olefinic products of the addition of benzocyclobutadiene to cyclopentadiene and benzyne to norbornadiene. Acetolysis of the endo-acenaphthylene adduct exo-toluene-p-sulphonate (15) produces rearranged exo-adduct exo-acetate via a Wagner-Meerwein shift of the 1,6-bond. The stereochemistry of the Diels-Alder addition is briefly discussed in the light of current theories.