Pyrrolidine-based C1-symmetric chiral transition metal complexes as catalysts in the asymmetric organic transformations

Various asymmetric organic transformations were effectively catalyzed by the chiral transition metal complexes of the privileged ligands. A wide range of transition metal complexes of C1-symmetric pyrrolidine-based ligands are used in many asymmetric organic reactions over the past decades. Pyrrolidine-based ligands are among the easiest to synthesize, and their structures can be easily adjusted sterically and electronically. Transition metal complexes of chiral C1-symmetric pyrrolidine-based ligands derived from (L)-proline (chiral source) are not comprehensively published in the form of a review article. In this digest review, we wish to discuss the use of transition metal complexes of the pyrrolidine-based ligands synthesized from (L)-proline in the asymmetric Strecker reaction, epoxidation of alkenes, asymmetric Henry reaction, sulfoxidation, C-H hydroxylation, oxidation of spirocyclic hydrocarbons, transfer hydrogenation of ketone/hydrazones