On the origins of diastereofacial selectivity of [4 + 2] cycloadditions in cage- annulated and polycarbocyclic diene/dienophile systems.

pi-Facial diastereoselectivities in Diels-Alder reactions that involve pi-facially differentiated cyclohexa-1,3-dienes, i.e., 3-substituted or 3-10-disubstituted hexacyclo-[10.2.1.0.(2,11)0.(4,9)0.(4,14)0(9,13)]pentadeca-5,7-dienes have been investigated. Two types of reactions have been examined experimentally and theoretically: (i) reactions of cage-annulated, pi-facially differentiated cyclohexa-1,3-dienes with pi-facially symmetric dienophiles and (ii) reactions of pi-facially symmetric dienes with cage-annulated, pi-facially differentiated dienophiles.