Fine-tuning catalytic activity and selectivity—[Rh(amino acid thioamide)] complexes for efficient ketone reduction

Fine-tuning of ligand structure results in higher catalytic activity and enantioselectivity in the rhodium-catalyzed asymmetric transfer hydrogenation of aryl alkyl ketones. Amino acid-derived thioamides are prepared and evaluated as ligands in the rhodium-catalyzed asymmetric transfer hydrogenation of ketones in 2-propanol. It is found that increasing the steric bulk at the C-terminus of the ligand had a positive impact on both activity and selectivity in the reduction reaction. In order to find the optimum catalyst, a study is performed on a series of thioamide ligands having substituents of varying size.