Dithiourea Ligands in the Rhodium-Catalyzed Hydride-Transfer Reduction of Ketones − A Theoretical and Experimental Approach

Abstract

Various dithioureas bearing an aromatic ring on their terminal nitrogen atoms have been synthesized. These have been tested in the asymmetric reduction of ketones as catalyzed by a rhodium complex. The influence of electron-withdrawing and electron-donating substituents on the aromatic rings on the reactivity and the enantiomeric excess (ee) has been assessed. The coordination modes of a model thiourea have been studied by Density Functional Theory (DFT) calculations. The electronic effects have also been analyzed and an interpretation of the variation in the enantiomeric excess, based on a supposed change in the coordination mode, is given.