Synthesis of Chiral Aromatic Alcohols: Use of New C2-Symmetric RhIIICp*, RuII(cymene), or RuII(benzene) Complexes Containing Chiral Diaminocyclohexane Ligand as Asymmetric Transfer Hydrogenation Catalyst

Abstract

Twelve chiral secondary alcohols were synthesized by asymmetric transfer hydrogenation (ATH) using C2-symmetric bis(sulfonamide) ligand (2) derived from (1R,2R)-cyclohexane-1,2-diamine and complexed with [RhCl2Cp*]2, [RuCl2(cymene)]2, or [RuCl2(benzene)]2 and then used in situ in the reduction of prochiral ketones. The alcohols were obtained in 85–99% yield and 90–99% enantioselectivity with isopropanol as the hydrogen source. Two-fold rate enhancement and better yields were achieved (88–99%) with 80–99% enantioselectivity using the complex [RhCl2Cp*]2 and aqueous sodium formate as the hydrogen source.