Interplay of ortho-with spiro-cyclisation during iminyl radical closures onto arenes and heteroarenes

Roy T. McBurney*, John C. Walton

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

25 Citations (Scopus)
32 Downloads (Pure)


Sensitised photolyses of ethoxycarbonyl oximes of aromatic and heteroaromatic ketones yielded iminyl radicals, which were characterised by EPR spectroscopy. Iminyls with suitably placed arene or heteroarene acceptors underwent cyclisations yielding phenanthridine-type products from ortho-additions. For benzofuran and benzothiophene acceptors, spiro-cyclisation predominated at low temperatures, but thermodynamic control ensured ortho-products, benzofuro-or benzothieno-isoquinolines, formed at higher temperatures. Estimates by steady-state kinetic EPR established that iminyl radical cyclisations onto aromatics took place about an order of magnitude more slowly than prototypical C-centred radicals. The cyclisation energetics were investigated by DFT computations, which gave insights into factors influencing the two cyclisation modes.

Original languageEnglish
Pages (from-to)1083-1092
Number of pages10
JournalBeilstein Journal of Organic Chemistry
Publication statusPublished - 4 Jun 2013
Externally publishedYes

Bibliographical note

Copyright the Author(s) 2013. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.


  • Cyclisation
  • EPR spectroscopy
  • Free radicals
  • Heterocycles
  • Oxime carbonates


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