Conjugate Addition of α-Substitutedβ-Ketoesters to α,β-Unsaturated Ketones

Significance

This paper describes the construction of quaternary stereocenters using an enantio­selective conjugate addition of α-substituted β-ketoesters to α,β-unsaturated ketones catalyzed by 1-20 mol% of a 6′-hydroxy cinchona alkaloid. The reactions were mainly performed at room temperature under open flask conditions yielding the products in high enantioselectivities and diastereoselectivities. Importantly, excellent results were achieved not only for a variety of α-substituted β-ketoesters but also for a wide range of α,β-unsaturated ketones bearing both alkyl and aryl substituents. A bulky ester group in the nucleophile (R³ = tert-butyl- or isopropyl) is required to achive high enantioselectivity.