Oxidation of Aromatic Alkynes with Nitrate Radicals (NO3•): An Experimental and Computational Study on a Synthetically Highly Versatile Radical

Uta Wille; Jilliarne Andropof

doi:10.1071/CH07045

RESEARCH ARTICLE

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Oxidation of Aromatic Alkynes with Nitrate Radicals (NO₃^•): An Experimental and Computational Study on a Synthetically Highly Versatile Radical

Uta Wille ^A ^B ^C and Jilliarne Andropof ^A ^B

+ Author Affiliations

- Author Affiliations

^A School of Chemistry, University of Melbourne, Melbourne VIC 3010, Australia.

^B Bio21 Molecular Science and Biotechnology Institute, 30 Flemington Road, Melbourne VIC 3010, Australia.

^C Corresponding author. Email: uwille@unimelb.edu.au

Australian Journal of Chemistry 60(6) 420-428 https://doi.org/10.1071/CH07045
Submitted: 14 February 2007 Accepted: 10 May 2007 Published: 18 June 2007

Abstract

Addition of electro- and photochemically generated nitrate radicals, NO₃^•, to the C≡C triple bond of aromatic alkynes 9a–9h leads to formation of 1,2-diketones 10a–10h. Surprisingly, benzophenones 11a–11h are obtained as by-products, which formally result from loss of a carbon atom. Density functional studies performed with the BHandHLYP method in combination with various basis sets revealed that 1,2-diketones result from 5-endo cyclization of the initially formed vinyl radical and loss of NO^•. The key step to benzophenone formation is a γ-cleavage at the stage of the vinyl radical with release of NO₂^•, followed by Wolff rearrangement of the resulting α-oxo carbene.

Acknowledgments

This work was supported by the Australian Research Council under the ARC Centres of Excellence program, the Victorian Institute for Chemical Sciences High Performance Computing Facility, and the Australian Partnership for Advanced Computing. We thank Hakki Turupçu and Christine Duke for their support.

References

Oxidation of Aromatic Alkynes with Nitrate Radicals (NO3•): An Experimental and Computational Study on a Synthetically Highly Versatile Radical

Abstract

Acknowledgments

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Oxidation of Aromatic Alkynes with Nitrate Radicals (NO₃^•): An Experimental and Computational Study on a Synthetically Highly Versatile Radical