Asymmetric Synthesis of Quaternary Stereocenters via Metal Enolates
The strategy of using chiral metal enolate intermediates in a diverse variety of asymmetric transformations has allowed the generation of quaternary stereocenter-bearing products that are otherwise difficult to access. Many classic transformations including aldol, Mannich, conjugate addition, alkylation, and pericyclic-type reactions, as well as allylic alkylation and α-arylation/alkenylation, have been adapted to proceed through chiral metal enolate intermediates, allowing the asymmetric synthesis of many complex products in both an intermolecular and intramolecular manner. These transformations have proven useful in the synthesis of natural products and may also be applied to the synthesis of novel pharmaceuticals and other compounds of interest in the future. This review includes work done up to and including the year 2014.