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Thermal Reactivity of Neutral and Oxidized Ferrocenyl-Substituted Enediynes
The coupling of two equivalents of ethynylferrocene (2) with one equivalent of 1,2-diiodocyclohexene (1) and 1,2-diiodobenzene (4) using Sonogashira cross-coupling conditions led to 1,2-bis(ferrocenylethynyl)cyclohexene (3) and 1,2-bis(ferrocenylethy-nyl)benzene (5), respectively. At high temperatur...
Autores principales: | , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
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MDPI
2014
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6271431/ https://www.ncbi.nlm.nih.gov/pubmed/25397734 http://dx.doi.org/10.3390/molecules191118399 |
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author | Cinar, Mehmet Emin Morbach, Guido Schmittel, Michael |
author_facet | Cinar, Mehmet Emin Morbach, Guido Schmittel, Michael |
author_sort | Cinar, Mehmet Emin |
collection | PubMed |
description | The coupling of two equivalents of ethynylferrocene (2) with one equivalent of 1,2-diiodocyclohexene (1) and 1,2-diiodobenzene (4) using Sonogashira cross-coupling conditions led to 1,2-bis(ferrocenylethynyl)cyclohexene (3) and 1,2-bis(ferrocenylethy-nyl)benzene (5), respectively. At high temperatures enediynes 3 and 5 showed exothermic signals in differential scanning calorimetry (DSC) measurements, suggestive of intramolecular diradicaloid ring formation (Bergman (C(1)−C(6)) or Schreiner-Pascal (C(1)−C(5)) cyclizations). The oxidation of 3 and 5 to the mono-oxidized enediynes 3(+) and 5(+) decreased the onset temperatures drastically. Equally, 1-ferrocenylethynyl-2-(p-nitro-phenyl)ethynylbenzene (8) displayed a significant decrease in the onset temperature after oxidation to 8(+). Because the insoluble nature of the polymeric material formed in the thermolysis of the oxidized enediynes prevented characterization, the origin of this drastic effect was studied by DFT. Contrary to expectations, one-electron oxidation does not lower the barrier for intramolecular cyclization. Rather, the computations suggest that the polymerization is initiated by a bimolecular process. |
format | Online Article Text |
id | pubmed-6271431 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2014 |
publisher | MDPI |
record_format | MEDLINE/PubMed |
spelling | pubmed-62714312019-01-07 Thermal Reactivity of Neutral and Oxidized Ferrocenyl-Substituted Enediynes Cinar, Mehmet Emin Morbach, Guido Schmittel, Michael Molecules Article The coupling of two equivalents of ethynylferrocene (2) with one equivalent of 1,2-diiodocyclohexene (1) and 1,2-diiodobenzene (4) using Sonogashira cross-coupling conditions led to 1,2-bis(ferrocenylethynyl)cyclohexene (3) and 1,2-bis(ferrocenylethy-nyl)benzene (5), respectively. At high temperatures enediynes 3 and 5 showed exothermic signals in differential scanning calorimetry (DSC) measurements, suggestive of intramolecular diradicaloid ring formation (Bergman (C(1)−C(6)) or Schreiner-Pascal (C(1)−C(5)) cyclizations). The oxidation of 3 and 5 to the mono-oxidized enediynes 3(+) and 5(+) decreased the onset temperatures drastically. Equally, 1-ferrocenylethynyl-2-(p-nitro-phenyl)ethynylbenzene (8) displayed a significant decrease in the onset temperature after oxidation to 8(+). Because the insoluble nature of the polymeric material formed in the thermolysis of the oxidized enediynes prevented characterization, the origin of this drastic effect was studied by DFT. Contrary to expectations, one-electron oxidation does not lower the barrier for intramolecular cyclization. Rather, the computations suggest that the polymerization is initiated by a bimolecular process. MDPI 2014-11-12 /pmc/articles/PMC6271431/ /pubmed/25397734 http://dx.doi.org/10.3390/molecules191118399 Text en © 2014 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution license (http://creativecommons.org/licenses/by/4.0/). |
spellingShingle | Article Cinar, Mehmet Emin Morbach, Guido Schmittel, Michael Thermal Reactivity of Neutral and Oxidized Ferrocenyl-Substituted Enediynes |
title | Thermal Reactivity of Neutral and Oxidized Ferrocenyl-Substituted Enediynes |
title_full | Thermal Reactivity of Neutral and Oxidized Ferrocenyl-Substituted Enediynes |
title_fullStr | Thermal Reactivity of Neutral and Oxidized Ferrocenyl-Substituted Enediynes |
title_full_unstemmed | Thermal Reactivity of Neutral and Oxidized Ferrocenyl-Substituted Enediynes |
title_short | Thermal Reactivity of Neutral and Oxidized Ferrocenyl-Substituted Enediynes |
title_sort | thermal reactivity of neutral and oxidized ferrocenyl-substituted enediynes |
topic | Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6271431/ https://www.ncbi.nlm.nih.gov/pubmed/25397734 http://dx.doi.org/10.3390/molecules191118399 |
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