Enantioselective Diels—Alder Reaction of Acyclic Enones Catalyzed by allo‐Threonine‐Derived Chiral Oxazaborolidinone.

An allo-threonine-derived O-(p-biphenylcarbonyloxy)-B-phenyl-oxazaborolidinone is demonstrated to be a powerful and highly enantioselective Lewis acid catalyst for the enantioselective Diels–Alder reaction of simple acyclic enone dienophiles, expanding the scope of ketone dienophiles and dienes. With 10–20 mol % of the catalyst, the Diels–Alder adducts are obtained with up to 94 % ee and high endo selectivity. The catalyst exhibits a high activity in the reaction with the less reactive β-substituted dienophiles and the less reactive 1,3-cycohexadiene and 1,3-butadiene derivatives. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

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