Tunable ferrocenyl-phosphinite ligands for the ruthenium(II)-catalyzed asymmetric transfer hydrogenation of ketones

• New examples of enantiomerically pure phosphinite ligands were synthesized.
• They contain both a ferrocene moiety and amino alcohol donor set.
• Readily available and air stable phosphinite type catalysts are introduced.
• They are efficient catalyst for the asymmetric transfer hydrogenation of ketones.
• Up to 99% conversion with 97% ee was obtained in the transfer hydrogenation.

We report here new examples of enantiomerically pure monodendate phosphinite ligands containing both a ferrocene moiety and NH bridging moiety adjacent to the stereocenter, as well as their ruthenium(II) dichloro complexes. The phosphinites based on ferrocenyl moiety possessing stereogenic center have been screened as ligands for ruthenium(II)-catalyzed transfer hydrogenation of aromatic ketones to give corresponding secondary alcohols using iso-PrOH as the hydrogen source in the presence of NaOH. Up to 99% conversion with 97% ee was obtained in the transfer hydrogenation of acetophenone derivatives. Furthermore, the catalytic properties of these catalysts based on ferrocenyl-phosphinite backbone are also discussed briefly. The structures of these ligand and their corresponding complexes have been elucidated by a combination of multinuclear NMR spectroscopy, IR spectroscopy and elemental analysis.

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