S. Kobayashi et al., ASYMMETRIC DIELS-ALDER REACTION CATALYZED BY A CHIRAL YTTERBIUM TRIFLUOROMETHANESULFONATE, Tetrahedron letters, 34(28), 1993, pp. 4535-4538
In the presence of a catalytic amount of chiral ytterbium trifluoromet
hanesulfonate (triflate), acyl-1,3-oxazolidin-2-ones or methacrolein r
eacted with cyclopehtadiene corresponding Diels-Alder adduct in high y
ields and with moderate to excellent enantiomeric excesses.