Highly Efficient Asymmetric Hetero-Diels−Alder Reactions of Carbonyl Compounds Catalyzed by Lewis Acid Platinum Complexes of Conformationally Flexible NUPHOS-Type Diphosphines

Conformationally flexible NUPHOS-type diphosphines have been resolved as their
diastereopure platinum BINOLate complexes δ- and λ-[(NUPHOS)Pt{(S)-BINOL}] and the
corresponding enantiopure Lewis acids δ- and λ-[(NUPHOS)Pt(OTf)2], being generated by
protonation with trifluoromethanesulfonic acid, act as highly efficient catalysts for the hetero-Diels−Alder reaction of nonactivated conjugated dienes with aryl glyoxals and glyoxylate
esters, giving ee's as high as 99%.