Modular hydroxyamide and thioamide pyranoside-based ligand library from the sugar pool: new class of ligands for asymmetric transfer hydrogenation of ketones

Identifier:  PC:687

Handle: https://hdl.handle.net/20.500.11797/PC687

Authors:  Coll, M.; Pàmies, O.; Diéguez, M.

Abstract:
A large library of pyranoside‐based hydroxyamide and thioamide ligands has been synthesized for asymmetric transfer hydrogenation in an attempt to expand the scope of the substrates to cover a broader range of challenging heteroaromatic and aryl/fluoroalkyl ketones. These ligands have the advantage that they are prepared from commercial D‐glucose, D‐glucosamine and α‐amino acids, inexpensive natural chiral feedstocks. By carefully selecting the ligand components (substituents/configurations at the amide/thioamide moiety, the position of amide/thioamide group and the configuration at C‐2), we found that pyranoside‐based thioamide ligands provided excellent enantioselectivities (in the best cases, ees of >99% were achieved) in a broad range of ketones, including the less studied heteroaromatics and challenging aryl/fluoroalkyls. Note that both enantiomers of the reduction products can be obtained with excellent enantioselectivities by simply changing the absolute configuration of the thioamide substituent.