Accessible Bifunctional Oxy-Tethered Ruthenium(II) Catalysts for Asymmetric Transfer Hydrogenation

Abstract

A concise synthesis of new oxy-tethered ruthenium complexes effective for the asymmetric transfer hydrogenation of aromatic ketones is described. The oxy-tether was constructed via a defluorinative etherification arising from an intramolecular nucleophilic substitution of a perfluorinated phenylsulfonyl substituent. The obtained tethered complexes exhibited desirable catalytic activity and selectivity, especially in the asymmetric transfer hydrogenation of functionalized aromatic ketones. The robustness and rigidity of the tether contribute to their superior catalytic performance relative to the nontethered prototype complex.

Bifunctional Homogeneous Catalysts Based on Ruthenium, Rhodium and Iridium in Asymmetric Hydrogenation

“…displaying N-SO2-(C6F4)-o-O(CH2)n (n = 1 or 2) tethers (see Scheme 14). 121 In parallel, Zhou and co-workers applied with success O-tethered ruthenium catalysts in the synthesis of optically enriched aryl N-heteroaryl methanols which are pharmaceutical intermediates of interest. 122 Aryl groups with opposite electronic and steric characters could be discriminated efficiently, which led to highly enantioselective ATH reactions.…”

Asymmetric Hydrogenation of Aryl Perfluoroalkyl Ketones Catalyzed by Rhodium(III) Monohydride Complexes Bearing Josiphos Ligands

“…Indeed, perfluoroalkyl ketones are known as low‐ yielding substrates in classical asymmetric hydrogenation protocols. Not surprisingly, optimized catalytic systems for acetophenones do not proceed efficiently for trifluoroacetophenones and suffer from poor enantioselectivities due to their vastly different stereoelectronic properties . In this work, we address this challenge by presenting an efficient protocol for the asymmetric hydrogenation of aryl perfluoroalkyl ketones using rhodium(III) complexes bearing Josiphos‐type ligands (Scheme ).…”

Ru‐TsDPEN catalysts and derivatives in asymmetric transfer hydrogenation reactions

“…15 which are highly effective for ATH process of aromatic ketones (Scheme 11). 60 During the construction of oxy-tether ligand (Cat. 13,14), initially N-pentafluorobenzenesulfonyl-1,-2-diphenylethylene-1,2-diamine (FsDPEN) in their (S, S) form are mixed thoroughly with prepared [RuCl 2 (η 6arene)] 2 in presence of same molar amount of triethyl amine (TEA) which was further refluxed in THF solvent for 2 hr producing half-sandwich Ru-complex.…”