DESIGN OF BRIDGED POLYCYCLIC DIOLEFIN PRECURSORS FOR PRISMANES USING FMO ORDER AS CRITERIA - INTERBRIDGE DISTANCE AS A NEW FACTOR FOR CONTROLLING THE INTRAMOLECULAR [PI-2+PI-2] CYCLOADDITION

If alkylene bridges of appropriate length are strategically spanned across their juxtaposed double bonds, it may be possible to effect [pi2 + pi2] photochemical cycloaddition of hypostrophene and homologous polycyclic diolefins leading to penta- and hexaprismane derivatives. Frontier molecular orbital (FMO) criteria were used to assess the possibilities of such syntheses. FMO orders were interpreted in terms of the formalism of pi/sigma orbital interactions through space and/or bonds. Cases that do not follow this formalism were explained by invoking a new factor, the interbridge distance (d2). Replacement of the trimethylene bridge by -CH2OCH2- was found to be effective in enlarging the energy gaps between the FMOs.