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Solvent‐Regulated Asymmetric Hydrogenation of Quinoline Derivatives in Oligo(Ethylene Glycol)s through Host–Guest Interactions
Author(s) -
Wang Tianli,
Chen Ya,
Ouyang Guanghui,
He YanMei,
Li Zhiyan,
Fan QingHua
Publication year - 2016
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.201600445
Subject(s) - ethylene glycol , chemistry , quinoline , asymmetric hydrogenation , catalysis , cationic polymerization , reactivity (psychology) , ruthenium , polymer chemistry , triethylene glycol , solvent , organic chemistry , ethylene , combinatorial chemistry , enantioselective synthesis , medicine , alternative medicine , pathology
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.