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Concurrent Radical Addition and [3+2] Cycloaddition between Nitrones and Maleimide‐Based Acyclic Enediynes

Concurrent Radical Addition and [3+2] Cycloaddition between Nitrones and Maleimide‐Based Acyclic... Enediyne compounds undergo Bergman cyclization while being activated with thermal or UV‐light triggers, and generate benzyne diradical intermediates, endowing their great potential as antitumor agents. The radical nature of the Bergman cyclization is generally confirmed through radical trapping experiments. While using phenyl tert‐butyl nitrone (PBN) as a radical trapping agent to study the Bergman cyclization of maleimide‐based enediyne compounds, we uncovered concurrent radical addition and [3+2] cycloaddition reactions between nitrones and enediyne compounds. The radical addition between the diradical intermediates and PBN was revealed through EPR analysis, while the [3+2] cycloaddition products were separated out and their structures were confirmed by NMR, HRMS and single crystal XRD analysis. Computational investigations showed that the energy barrier of the [3+2] cycloaddition was much lower than that of the Bergman reaction, corroborating the dominance of [3+2] cycloaddition between nitrone and enediyne compounds. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Asian Journal of Organic Chemistry Wiley

Concurrent Radical Addition and [3+2] Cycloaddition between Nitrones and Maleimide‐Based Acyclic Enediynes

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References (42)

Publisher
Wiley
Copyright
© 2018 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim
ISSN
2193-5807
eISSN
2193-5815
DOI
10.1002/ajoc.201800408
Publisher site
See Article on Publisher Site

Abstract

Enediyne compounds undergo Bergman cyclization while being activated with thermal or UV‐light triggers, and generate benzyne diradical intermediates, endowing their great potential as antitumor agents. The radical nature of the Bergman cyclization is generally confirmed through radical trapping experiments. While using phenyl tert‐butyl nitrone (PBN) as a radical trapping agent to study the Bergman cyclization of maleimide‐based enediyne compounds, we uncovered concurrent radical addition and [3+2] cycloaddition reactions between nitrones and enediyne compounds. The radical addition between the diradical intermediates and PBN was revealed through EPR analysis, while the [3+2] cycloaddition products were separated out and their structures were confirmed by NMR, HRMS and single crystal XRD analysis. Computational investigations showed that the energy barrier of the [3+2] cycloaddition was much lower than that of the Bergman reaction, corroborating the dominance of [3+2] cycloaddition between nitrone and enediyne compounds.

Journal

Asian Journal of Organic ChemistryWiley

Published: Oct 1, 2018

Keywords: ; ; ; ;

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