CYCLOADDITION REACTIONS OF ALLYL AND RELATED CATIONS

Both allyl cations and cation radicals add to 1,3-dienes at temperatures as low as -78oC to produce 2pi + 4pi cycloadducts (Diels-Alder products). In view of our many discoveries in this area, we plan to continue our studies of cycloadditions of allyl cations to 1,3-dienes, and to extend our investigation to a careful investigation of the intramolecular cycloaddition of cation-radicals generated from 1,3-dienes to 1,3-dienes. Studies will continue to (a) controlling the regiochemistry of both the intramolecular and intermolecular 2pi + 4pi cycloadditions, (b) understanding the nature of the allyl cation in order to utilize the unsymmetrical nature of this reactive species, and (c) exploration of the addition of electron rich dienophiles to pentadienyl cations. Studies new to this proposal include: (a) the use of cyclopropanes as allyl cation precursors in the ionic Diels-Alder reaction, (b) the use of aziridines as 2-azaallyl cation precursors, (c) the intramolecular 2pi + 4pi cycloaddition of cation radicals generated from 1,3-dienes to 1,3-dienes, and (d) preliminary investigation of the addition of electron rich dienophiles to cation radicals generated from 1,3,5-triene.