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The efficiency and stereoselectivity of the conjugate addition of lithium (Z)- or (E)-beta-amino ester enolates, generated by lithium amide conjugate addition to an alpha,beta-unsaturated ester or deprotonation of a beta-amino ester, respectively, to a range of alpha,beta-unsaturated acceptors has been investigated. Deprotonation of a beta-amino ester with LDA, followed by conjugate addition to a chiral alpha,beta-unsaturated oxazolidinone gives high 2,3-anti selectivity ( approximately 90% d.e.), with hydrogenolysis and purification to homogeneity generating stereodefined trisubstituted piperidinones as single stereoisomers. Asymmetric three-component couplings of alpha,beta-unsaturated esters and alkylidene malonates initiated by lithium amide conjugate addition proceeds with high levels of 2,3-anti stereoselectivity, with hydrogenolysis giving tetrasubstituted piperidinones.

Original publication

DOI

10.1039/b701226h

Type

Journal article

Journal

Org Biomol Chem

Publication Date

07/05/2007

Volume

5

Pages

1405 - 1415

Keywords

Crystallography, X-Ray, Esters, Lithium, Oxazolidinones, Piperidines, Piperidones, Stereoisomerism, Temperature