C2-Symmetric Cationic Copper(II) Complexes as Chiral Lewis Acids: Counterion Effects in the Enantioselective Diels–Alder Reaction

Authors

  • Prof. David A. Evans,

    Corresponding author
    1. Department of Chemistry, Harvard University, Cambridge, MA 02138 (USA), Telefax: Int. code + (617)495-1460
    • Department of Chemistry, Harvard University, Cambridge, MA 02138 (USA), Telefax: Int. code + (617)495-1460
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  • Jerry A. Murry,

    1. Department of Chemistry, Harvard University, Cambridge, MA 02138 (USA), Telefax: Int. code + (617)495-1460
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  • Peter von Matt,

    1. Department of Chemistry, Harvard University, Cambridge, MA 02138 (USA), Telefax: Int. code + (617)495-1460
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  • Roger D. Norcross,

    1. Department of Chemistry, Harvard University, Cambridge, MA 02138 (USA), Telefax: Int. code + (617)495-1460
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  • Scott J. Miller

    1. Department of Chemistry, Harvard University, Cambridge, MA 02138 (USA), Telefax: Int. code + (617)495-1460
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  • Financial support was provided by the National Science Foundation and the National Institutes of Health. Fellowships from the National Institutes of Health (J.A.M.), Swiss National Science Foundation, and Ciba-Geigy Jubiläumsstiftung (P.v.M.), NATO (R. D. N.), and the National Science Foundation (S.J.M.) are gratefully acknowledged. The NIH BRS Shared Instrument Grant Program 1 S10 RR01748-01A1 is acknowledged for providing NMR facilities.

Abstract

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Alone a tailor-made chiral cationic Lewis acid is not sufficient to achieve high enantiomic excesses in Diels–Alder reactions; the counterion can dramatically affect the efficiency of the chiral catalyst. Thus, for example, the enantioselectivities reached in these reactions in the presence of the copper complex 1 with X = SbF6 as counterion are in some cases substantially greater than those with X = OSO2CF3.

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