Application of Proline-Functionalised 1,2-Diphenylethane-1,2-diamine (DPEN) in Asymmetric Transfer Hydrogenation of Ketones

A series of enantiomerically pure ligands containing a combination of proline and DPEN groups have been prepared and employed in the asymmetric transfer hydrogenation of ketones. In the case of cyclic ketones, alcohols with ee values of up to 98 % were obtained. Ligands 20–23 were prepared and used for the asymmetric transfer hydrogenation of a range of ketones. Using ligand 23, bicyclic ketones were reduced in up to 96 % ee.