Laticyclic conjugated double bonds within the framework of oligocondensed bicyclo[2.2.2]octenes

The all-syn oligocondensed bicyclo[2.2.2]octenes 3, 5, 20 and 29 with two to five etheno bridges show interaction of their π-orbitals by σ-overlap. This laticyclic conjugation reveals itself in the PE and UV spectra of the series as well as in the site selectivity of the Diels–Alder reaction with inverse electron demand found for the dehydro derivatives 11 and 26. As shown in the crystal structures of 3, 5 and 20, the etheno bridges are positioned face to face at a distance which is smaller than the sum of their van der Waals radii.