Rutheuium(II)-catalyzed asymmetric transfer hydrogenation of carbonyl compounds with 2-propanol and ephedrine-type ligands

This account describes the development and application of Noyori's type catalysts based on ruthenium-arene complexes and simple chiral beta-amino alcohols derived from ephedrine, for the asymmetric transfer hydrogenation of 2-propanol to carbonyl substrates. The influence of key parameters of the catalyst system has been studied systematically, resulting in particular in the design of the novel ligand (4-biphenylmethyl)norephedrine. Thanks to the latter, the catalytic precursors and true active species could be isolated for the first time, enabling a complete structural description of the catalytic cycle and of probable deactivation pathways. Highly effective applications of those catalysts systems, i.e., the asymmetric reductions of simple aryl ketones and aryl beta-keto esters, the synthesis of chiral phthalides and syn-beta,delta-dihydroxy esters, are described. 1 Introduction 2 Development of [Ru(arene)(beta-Amino Alcohol)] Catalysts 2.1 Effect of the beta-Amino Alcohol Ligand 2.2 Effect of the Arene Ligand 3 Isolation and Reactivity of Catalytic Intermediates 4 Applications of [Ru(arene)(beta-Amino Alcohol)]Catalyzed Transfer Hydrogenation 4.1 Aromatic Ketones and Keto Esters 4.2 Simple and Functionalized Aliphatic Ketones and Keto Esters 4.3 Catalyst Deactivation Pathways 5 Conclusions.