Asymmetric Reduction of Electron-Rich Ketones with Tethered Ru(II)/TsDPEN Catalysts Using Formic Acid/Triethylamine or Aqueous Sodium Formate

The asymmetric transfer hydrogenation (ATH) of ketones under aqueous conditions using tethered Ru(II)/eta(6)-arene/diamine catalysts is described, as is the ATH of electron-rich substrates containing amine and methoxy groups on the aromatic rings. Although such substrates are traditionally challenging ones for ATH, the tethered catalysts work very efficiently. In the case of amino-substituted ketones, aqueous conditions give excellent results; however, for methoxy-substituted substrates, the more established formic acid/triethylamine system gives superior results.