Asymmetric Diels–Alder Reaction by the Use of a Chiral Titanium Catalyst with Molecular Sieves 4A. Remarkable Solvent Effect on the Enantioselectivity

A remarkable effect of solvent on the enantioselectivity was observed in the asymmetric Diels–Alder reaction of 3-(2-alkenoyl)-1,3-oxazolidin-2-ones and dienes catalyzed by a chiral titanium reagent, and the Diels–Alder adducts were obtained in high enantioselectivity when alkyl-substituted benzenes were employed as the solvent.