Asymmetric Hydrogenation of Benzalacetone Catalyzed by TPPTS-Stabilized Ru in Ionic Liquids

Abstract

Achiral monophosphine TPPTS [TPPTS: P(m-C₆H₄SO₃Na)₃]-stabilized Ru was successfully applied to catalyze the asymmetric hydrogenation of benzalacetone in ionic liquids using (S,S)-DPENDS [disodium salt of sulfonated (S,S)-1,2-diphenyl-1,2-ethylene-diamine] as chiral modifier. Under the optimized reaction conditions, the conversion of benzalacetone, chemoselectivity, and enantioselectivity of 4-phenyl-3-buten-2-ol could be reached up to 99.5%, 98.8%, and 74.6%, respectively. The TPPTS-stabilized Ru catalyst immobilized in ionic liquids could be easily separated from the resulting products by extraction with n-hexane, which could be recycled and reused five times without significant loss in activity, chemoselectivity, and enantioselectivity.

Keywords:

• ionic liquids
• asymmetric hydrogenation
• TPPTS-stabilized Ru
• benzalacetone
• recyclable
• chemoselectivity

Funding

The authors are grateful for support from the Natural Science Foundation of Chongqing Science & Technology Commission (cstc2011jjA10036, cstc2012jjA50008), the Research Foundation of Chongqing University of Science & Technology (CK2011Z11, CK2011Z19), and the Natural Science Foundation of Education Commission of Chongqing (KJ121401, KJ131421).