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Late-Stage Diversification of Chiral N-Heterocyclic-Carbene Precatalysts for Enantioselective Homoenolate Additions

Authors

  • Dr. Pinguan Zheng,

    1. Roy and Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104 (USA)
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  • Chenaimwoyo A. Gondo,

    1. Roy and Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104 (USA)
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  • Prof. Dr. Jeffrey W. Bode

    Corresponding author
    1. Roy and Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104 (USA)
    2. Present address: Laboratorium für Organische Chemie, ETH-Zürich, Wolfgang Pauli Strasse 10, Zürich 8093 (Switzerland)
    • Roy and Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104 (USA)
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Abstract

A library of chiral triazolium salts has been prepared by late-state diversification of a triazolium amine salt. By utilizing a primary amine as a functional handle, a single triazolium salt can be transformed into a variety of chiral N-heterocyclic carbene precatalysts. This approach makes the preparation of chiral N-heterocyclic carbenes possible by a single-step modification of a triazolium salt, rather than the usual need for multistep organic synthesis and challenging heterocycle formation for each member of a catalyst library. We have screened these catalysts for control of diastereo- and enantioselectivity in a γ-lactam-forming reaction between α,β-unsaturated aldehydes and cyclic ketimines.

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