Enantiomerically Pure <i>ansa</i>-<i>η</i>⁵-Complexes of Transition Metals as an Effective Tool for Chirality Transfer

Abstract

Chiral ansa-η5-complexes of transition metals have shown remarkable efficacy in organometallic synthesis and catalysis. Additionally, enantiomerically pure ansa-complexes hold promise for the development of novel chiral materials and pharmaceuticals. The discovery and synthesis of a diverse range of group IVB and IIIB metal complexes represents a significant milestone in the advancement of stereoselective catalytic methods for constructing metal-C, C-C, C-H, and C-heteroatom bonds. The synthesis of enantiomerically pure metallocenes can be accomplished through several strategies: utilizing optically active precursors of η5-ligands, separation of diastereomers of complexes with enantiomerically pure agents, and synthesis via the stereocontrolled reactions of enantiomerically pure σ-complexes with prochiral anions of η5-ligands. This review focuses on the analysis of various nuances of the synthesis of enantiomerically pure ansa-η5-complexes of titanium and lanthanum families. Their applicability as effective catalysts in asymmetric carbomagnesiation, carbo- and cycloalumination, oligo- and polymerization, Diels–Alder cycloaddition, reactions of zirconaaziridines, cyclization, hydrosilylation, hydrogenation, hydroamination, and other processes are highlighted as well.

Keywords

• <i>ansa</i>-metallocenes
• enantiomerically pure complexes
• stereoselectivity
• asymmetric synthesis
• reaction mechanisms