Isolation of a Zwitterion in a Diels–Alder Reaction with Inverse Electron Demand

Authors

  • Dipl.-Chem. Klaus-Peter Hartmann,

    1. Institut für Organische Chemie der Universität, Karlstrasse 23, D-8000 München 2(FRG)
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  • Priv.-Doz. Dr. Manfred Heuschmann

    Corresponding author
    1. Institut für Organische Chemie der Universität, Karlstrasse 23, D-8000 München 2(FRG)
    • Institut für Organische Chemie der Universität, Karlstrasse 23, D-8000 München 2(FRG)
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  • This work was supported by the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie.

Abstract

original image

The Diels–Alder reaction between tetrazine 1 and the ketene-N,N acetal 2 is not concerted but rather a two-step process. At temperatures < −15 °C it proved possible to isolate the zwitterion 3, which reacted further to 4 upon warming. Previously confusing phenomena associated with such reactions now merit reconsideration and systematic investigation.

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