Interplay of ortho- with spiro-cyclisation during iminyl radical closures onto arenes and heteroarenes
Abstract
Sensitised photolyses of ethoxycarbonyl oximes of aromatic and heteroaromatic ketones yielded iminyl radicals which were characterised by EPR spectrscopy. 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 magnitule more slowly than prototypical C-centred radicals. Cyclisation energetics were investigated by DFT computations which gave insights into factors influencing the two cyclisation modes.
Citation
McBurney , R T & Walton , J C 2013 , ' Interplay of ortho- with spiro-cyclisation during iminyl radical closures onto arenes and heteroarenes ' , Beilstein Journal of Organic Chemistry , vol. 9 , pp. 1083-1092 . https://doi.org/10.3762/bjoc.9.120
Publication
Beilstein Journal of Organic Chemistry
Status
Peer reviewed
ISSN
1860-5397Type
Journal article
Rights
© 2013 McBurney and Walton; licensee Beilstein-Institut. This is an Open Access article under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The license is subject to the Beilstein Journal of Organic Chemistry terms and conditions: (http://www.beilstein-journals.org/bjoc).
Description
Funding: The authors thank the EPSRC (grant EP/I003479/1) & EaStCHEM for funding, the EPSRC UK National Electron Paramagnetic Resonance Service at the University of Manchester and the EPSRC National Mass Spectrometry Service, Swansea.Collections
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