Construction of Quaternary Stereocenters: New Perspectives through Enantioselective Michael Reactions
Christoffers and Baro have reviewed recent work on enantioselective Michael reactions, which enable quaternary stereocentres to be generated with >90% ee. Compounds such as the four examples shown below can be produced by reaction between the appropriate 1,3-dicarbonyl compound and an enone catalysed by Pd(II)-diaquadiphosphanes such as (R)-tol-binap-Pd(OH)2 and (R)-binap-Pd(OH)2. Other catalysts such as the La- binol system developed by Shibasaki and the zinc versions using linked-binol ligands are also covered.
Also included are examples of chiral auxiliary mediated asymmetric Michael reactions. (Angew. Chem. Internat. Ed., 2003, 42, 1688-1690).