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Enantioselective Diels−Alder Reaction of Simple α,β-Unsaturated Ketones with a Cinchona Alkaloid Catalyst

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posted on 27.02.2008, 00:00 by Ravi P. Singh, Keith Bartelson, Yi Wang, Heng Su, Xiaojie Lu, Li Deng
The simple α,β-unsaturated ketones and 2-pyrones are readily available and synthetically important dienophiles and dienes, respectively, for Diels−Alder reactions. However, both prove to be challenging substrates for catalytic asymmetric Diels−Alder reactions. By exploring a new catalysis strategy featuring cooperative catalysis with readily available cinchona catalysts, an unprecedented asymmetric Diels−Alder reaction of simple α,β-unsaturated ketones with 2-pyrones has been successfully developed. With broad scopes for both reactants, the reaction provides a direct and versatile asymmetric access to a wide range of structurally novel bicyclic chiral building blocks amenable for further synthetic elaborations.