The synthesis of tetradentate salens derived from (3R,4R)-N-substituted-3,4-diaminopyrrolidines and their application in the enantioselective trimethylsilylcyanation of aromatic aldehydes

Investigation of Enantioselectivity Using TADDOL Derivatives as Chiral Ligands in Asymmetric Cyanation Reactions

This study investigates the enantioselectivity challenges of asymmetric cyanation reactions using TADDOL derivatives as chiral ligands, specifically focusing on the cyanosilylation of aldehydes and the cyanation of imines. Despite extensive optimization efforts, the highest achieved ee was only modest, peaking at 71% for the cyanosilylation reaction, while the cyanation of imines consistently resulted in racemic mixtures. Our comprehensive analysis, supported by experimental data and computational modeling, reveals significant barriers to enhancing the enantioselectivity. The results highlight a complex interplay between ligand structure and reaction conditions, demonstrating that even promising ligands such as TADDOL derivatives face substantial challenges in these reaction types. This study underscores the importance of understanding the mechanistic details through computational insights to guide future improvements in asymmetric catalysis.