Development of C2-Symmetric Chiral Diphosphine Ligands for Highly Enantioselective Hydrogenation Assisted by Ion Pairing

A new series of C2-symmetrical chiral ferrocene-based diphosphino-ethane ligands termed as f-DPE were developed. Assisted by the ion pairing interaction with the ligand, a wide scope of 2-substituted acrylic acids was hydrogenated to obtain chiral propanoic acids with high yields and enantioselectivities. The well-known anti-inflammatory drugs ibuprofen, naproxen, and flurbiprofen could be synthesized efficiently. In addition, the synthetic utilities of the current method were demonstrated by gram-scale experiments.