title: Solvent-Regulated Asymmetric Hydrogenation of Quinoline Derivatives in Oligo(Ethylene Glycol)s through Host-Guest Interactions.
abstract: The asymmetric hydrogenation of quinolines in oligo(ethylene glycol)s (OEGs) and poly(ethylene glycol)s (PEGs) with chiral cationic ruthenium diamine complexes has been investigated. Interestingly, in liquid PEGs or long-chain OEGs, the Ru catalysts lost their reactivity. Upon the addition of a little MeOH, the hydrogenation of quinoline was switched "ON". Evidence from mass spectrometry and control experiments revealed that encapsulation of the quinolinium salt by PEG or long-chain OEG molecules through supramolecular interactions is possibly the main reason for such a switchable hydrogenation reaction. Moreover, the asymmetric hydrogenation of 2-substituted quinoline derivatives was achieved in triethylene glycol (3-OEG), thereby affording 1,2,3,4-tetrahydroquinolines with excellent reactivities and enantioselectivities (up to 99 % ee). Furthermore, the Ru catalyst could be readily recycled for both pure 3-OEG and biphasic 3-OEG/n-hexane systems without a clear loss of reactivity and enantioselectivity.
authors.affiliation: CAS Key Laboratory for Molecular Recognition and Function, Institute of Chemistry, Chinese Academy of Science (CAS), and, University of the Chinese Academy of Sciences, Beijing, 100190, P. R. China.
authors.forename: Tianli
authors.initials: T
authors.lastname: Wang
authors.affiliation: CAS Key Laboratory for Molecular Recognition and Function, Institute of Chemistry, Chinese Academy of Science (CAS), and, University of the Chinese Academy of Sciences, Beijing, 100190, P. R. China.
authors.forename: Ya
authors.initials: Y
authors.lastname: Chen
authors.affiliation: CAS Key Laboratory for Molecular Recognition and Function, Institute of Chemistry, Chinese Academy of Science (CAS), and, University of the Chinese Academy of Sciences, Beijing, 100190, P. R. China.
authors.forename: Guanghui
authors.initials: G
authors.lastname: Ouyang
authors.affiliation: CAS Key Laboratory for Molecular Recognition and Function, Institute of Chemistry, Chinese Academy of Science (CAS), and, University of the Chinese Academy of Sciences, Beijing, 100190, P. R. China.
authors.forename: Yan-Mei
authors.initials: YM
authors.lastname: He
authors.affiliation: CAS Key Laboratory for Molecular Recognition and Function, Institute of Chemistry, Chinese Academy of Science (CAS), and, University of the Chinese Academy of Sciences, Beijing, 100190, P. R. China.
authors.forename: Zhiyan
authors.initials: Z
authors.lastname: Li
authors.affiliation: CAS Key Laboratory for Molecular Recognition and Function, Institute of Chemistry, Chinese Academy of Science (CAS), and, University of the Chinese Academy of Sciences, Beijing, 100190, P. R. China. fanqh@iccas.ac.cn.|Collaborative Innovation Center of Chemical Science and Engineering, Tianjin, 300072, P. R. China. fanqh@iccas.ac.cn.
authors.forename: Qing-Hua
authors.initials: QH
authors.lastname: Fan
keywords: asymmetric catalysis; hydrogenation; oligo(ethylene glycol)s; ruthenium; solvent effects