Chiral Phosphinooxazolidine Ligands for Palladium- and Platinum-Catalyzed Asymmetric Diels−Alder Reactions

Cationic palladium (Pd)- and platinum (Pt)-phosphinooxazolidine catalysts 13a−c, 15a−d, 17a−c, and 19a−c were prepared from phosphinooxazolidine ligands 1−3, MCl2 (M = Pd and Pt), and
counterions, and the activities of the catalysts in the asymmetric Diels−Alder (DA) reactions of
cyclic or acyclic dienes with imide dienophiles were investigated. These catalysts demonstrated
high levels of catalytic activity. The cationic Pd−POZ complex 13c provided particularly excellent
enantioselectivity (98% ee) in the DA reactions of cyclopentadiene with acryloyl-, crotonyl-, and
fumaroyl-1,3-oxazolidin-2-ones (20a−c).