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

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

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....

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Bibliographic Details
Main Authors: Roy T. McBurney, John C. Walton
Format: Article
Language:English
Published: Beilstein-Institut 2013-06-01
Series:Beilstein Journal of Organic Chemistry
Subjects:
cyclisation
EPR spectroscopy
free radicals
heterocycles
oxime carbonates
Online Access:https://doi.org/10.3762/bjoc.9.120
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spelling doaj-4952368d65f74eb0bc4cb8a784a27be52021-02-02T02:31:41ZengBeilstein-InstitutBeilstein Journal of Organic Chemistry1860-53972013-06-01911083109210.3762/bjoc.9.1201860-5397-9-120Interplay of ortho- with spiro-cyclisation during iminyl radical closures onto arenes and heteroarenesRoy T. McBurney0John C. Walton1EaStCHEM School of Chemistry, University of St. Andrews, St. Andrews, Fife, KY16 9ST, UKEaStCHEM School of Chemistry, University of St. Andrews, St. Andrews, Fife, KY16 9ST, UKSensitised 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.https://doi.org/10.3762/bjoc.9.120cyclisationEPR spectroscopyfree radicalsheterocyclesoxime carbonates
collection DOAJ
language English
format Article
sources DOAJ
author Roy T. McBurney
John C. Walton
spellingShingle Roy T. McBurney
John C. Walton
Interplay of ortho- with spiro-cyclisation during iminyl radical closures onto arenes and heteroarenes
Beilstein Journal of Organic Chemistry
cyclisation
EPR spectroscopy
free radicals
heterocycles
oxime carbonates
author_facet Roy T. McBurney
John C. Walton
author_sort Roy T. McBurney
title Interplay of ortho- with spiro-cyclisation during iminyl radical closures onto arenes and heteroarenes
title_short Interplay of ortho- with spiro-cyclisation during iminyl radical closures onto arenes and heteroarenes
title_full Interplay of ortho- with spiro-cyclisation during iminyl radical closures onto arenes and heteroarenes
title_fullStr Interplay of ortho- with spiro-cyclisation during iminyl radical closures onto arenes and heteroarenes
title_full_unstemmed Interplay of ortho- with spiro-cyclisation during iminyl radical closures onto arenes and heteroarenes
title_sort interplay of ortho- with spiro-cyclisation during iminyl radical closures onto arenes and heteroarenes
publisher Beilstein-Institut
series Beilstein Journal of Organic Chemistry
issn 1860-5397
publishDate 2013-06-01
description 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.
topic cyclisation
EPR spectroscopy
free radicals
heterocycles
oxime carbonates
url https://doi.org/10.3762/bjoc.9.120
work_keys_str_mv AT roytmcburney interplayoforthowithspirocyclisationduringiminylradicalclosuresontoarenesandheteroarenes
AT johncwalton interplayoforthowithspirocyclisationduringiminylradicalclosuresontoarenesandheteroarenes
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