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Gini A, Segler M, Kellner D, et al. Dehydrogenative TEMPO-Mediated Formation of Unstable Nitrones: Easy Access to N-Carbamoyl Isoxazolines. Chemistry. 2015;21(34):12053-60doi: 10.1002/chem.201501314.
Gini, A., Segler, M., Kellner, D., & Mancheño, O. G. (2015). Dehydrogenative TEMPO-Mediated Formation of Unstable Nitrones: Easy Access to N-Carbamoyl Isoxazolines. Chemistry (Weinheim an der Bergstrasse, Germany), 21(34), 12053-60. https://doi.org/10.1002/chem.201501314
Gini, Andrea, et al. "Dehydrogenative TEMPO-Mediated Formation of Unstable Nitrones: Easy Access to N-Carbamoyl Isoxazolines." Chemistry (Weinheim an der Bergstrasse, Germany) vol. 21,34 (2015): 12053-60. doi: https://doi.org/10.1002/chem.201501314
Gini A, Segler M, Kellner D, Mancheño OG. Dehydrogenative TEMPO-Mediated Formation of Unstable Nitrones: Easy Access to N-Carbamoyl Isoxazolines. Chemistry. 2015 Aug 17;21(34):12053-60. doi: 10.1002/chem.201501314. Epub 2015 Jul 17. PMID: 26212677.
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Chemistry. 2015 Aug 17;21(34):12053-60. doi: 10.1002/chem.201501314. Epub 2015 Jul 17.

Dehydrogenative TEMPO-Mediated Formation of Unstable Nitrones: Easy Access to N-Carbamoyl Isoxazolines.

Chemistry (Weinheim an der Bergstrasse, Germany)

Andrea Gini, Marwin Segler, Dominik Kellner, Olga García Mancheño

Affiliations

  1. Institute for Organic Chemistry, University of Regensburg, Universitätsstrasse 31, 93053 Regensburg (Germany).
  2. Straubing Center of Science for Renewable Resources (WZS), Schulgasse 16, 94315 Straubing (Germany).
  3. Institute of Organic Chemistry, University of Münster, Corrensstrasse 40, 248149 Münster (Germany).
  4. Institute for Organic Chemistry, University of Regensburg, Universitätsstrasse 31, 93053 Regensburg (Germany). [email protected].
  5. Straubing Center of Science for Renewable Resources (WZS), Schulgasse 16, 94315 Straubing (Germany). [email protected].

PMID: 26212677 DOI: 10.1002/chem.201501314

Abstract

N-carbamoyl nitrones represent an important class of reagents for the synthesis of a variety of natural and biologically active compounds. These compounds are generally converted into valuable 4-isoxazolines upon cyclization reaction with dipolarophiles. However, these types of N-protected nitrones are highly unstable, which limits their synthesis, storage and practical use, enforcing alternative lengthy or elaborated synthetic routes. In this work, a 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO)-mediated formal "dehydrogenation" of N-protected benzyl-, allyl- and alkyl-substituted hydroxylamines followed by in situ trapping of the generated unstable nitrones into N-carbamoyl 4-isoxazolines is presented. A plausible mechanism is also proposed, in which the dipolarophile shows an important assistant role in the generation of the active nitrone intermediate. This simple protocol avoids the problematic isolation of N-carbamoyl protected nitrones, providing new synthetic possibilities in isoxazoline chemistry.

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Keywords: TEMPO; cycloadditon; dehydrogenative; isoxazolines; unstable N-acyl nitrones

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