The Design and Synthesis of Planar Chiral Ligands and Their Application to Asymmetric Catalysis

Abstract

Ferrocene- and ruthenocene-based planar chiral ligands have been developed and used in transition-metal-catalyzed asymmetric allylic substitutions, asymmetric hydrogenations, and asymmetric conjugate addition reactions. The most common ferrocene ligands, which have bis(oxazoline) substituents on the cyclopentadiene rings, have been modified to create new planar chiral C 2-symmetric ligands, some of which have shown excellent potential in the aforementioned reactions. A series of planar chiral ruthenocene ligands have also been developed and their activities differ from those of their ferrocene counterparts. 1 Introduction 2 The Design and Synthesis of Planar Chiral Ligands 2.1 Ferrocene-Based Ligands 2.2 Ruthenocene-Based Ligands 3 Applications of Planar Chiral Ligands in Asymmetric Reactions 3.1 Asymmetric Allylic Alkylation 3.2 Asymmetric Allylic Amination 3.3 Asymmetric Allylic Alkylation with Enamines as Nucleophiles 3.4 Asymmetric Alkylation of Aryl Aldehydes 3.5 Asymmetric Hydrogenation 3.6 1,4-Asymmetric Conjugation Reactions 4 Summary