BINOLate–Magnesium Catalysts for Enantioselective Hetero-Diels–Alder Reaction of Danishefsky's Diene with Aldehydes
An efficient catalytic enantioselective hetero-Diels–Alder reaction of Danishefsky's diene with aldehydes using the magnesium binaphthoxide system has been developed, affording a variety of 2-substituted 2,3-dihydro-4H-pyran-4-ones in high yields and with excellent ee values. The aggregation behavior and nonlinear effect of the catalytic system, as well as the remarkable stereoelectronic effects of ligands on the catalysis, have also been investigated. On the basis of the structure of the isolated reaction intermediate, the stereochemistry of the products, and the information attained from a study of the nonlinear effect, a plausible asymmetric induction model has been proposed. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)