Cationic Chiral Pd-Catalyzed "Acetylenic" Diels-Alder Reaction: Computational Analysis of Reversal in Enantioselectivity.

The highly enantioselective Diels-Alder reaction of acetylenic dienophiles is shown to be effectively catalyzed by cationic chiral palladium complexes. Not only the degree but also the sense of enantioselectivity critically depends on the steric demand of ligands. Computational analyses indicate that the steric demand does not affect the endo/exo-selectivity but the enantioface selectivity of dienes.