Lookup NU author(s): Dr Simon Doherty,
Dr Julian Knight,
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Imidazolium-tagged bis(oxazolines) have been prepared and used as chiral ligands in the copper(II)-catalysed Diels-Alder reaction of N-acryloyland N-crotonoyloxazolidinones with cyclopentadiene and 1,3-cyclohexadiene in the ionic liquid 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide, [emim] [NTf2]. A significant and substantial enhancement in the rate and enantioselectivity was achieved in [emim] [NTf2] compared with dichloromethane. For example, complete conversion and enantioselectivities up to 95 % were obtained for the reaction between N-acryloyloxazolidinone and cyclopentadiene within 2 min in [emim] [NTf2] whereas the corresponding reaction in dichloromethane required 60 min to reach completion and gave an ee of only 16%. The enhanced rates obtained in the ionic liquid enabled a catalyst loading as low as 0.5 mol % to give complete conversion within 2 min while retaining the same level of enantioselectivity. The imidazolium-tagged catalysts can be recycled ten times without any loss in activity or enantioselectivity and showed much higher affinity for the ionic liquid phase during the recycle procedure than the analogous uncharged ligand. © 2007 Wiley-VCH Verlag GmbH & Co. KGaA.
Author(s): Doherty S, Goodrich P, Hardacre C, Knight JG, Nguyen MT, Parvulescu VI, Paun C
Publication type: Article
Publication status: Published
Journal: Advanced Synthesis and Catalysis
ISSN (print): 1615-4150
ISSN (electronic): 1615-4169
Publisher: Wiley - VCH Verlag GmbH & Co. KGaA
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