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Iron(II) Active Species in Iron–Bisphosphine Catalyzed Kumada and Suzuki–Miyaura Cross-Couplings of Phenyl Nucleophiles and Secondary Alkyl Halides
[Image: see text] While previous studies have identified FeMes(2)(SciOPP) as the active catalyst species in iron–SciOPP catalyzed Kumada cross-coupling of mesitylmagnesium bromide and primary alkyl halides, the active catalyst species in cross-couplings with phenyl nucleophiles, where low valent iro...
Autores principales: | , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
American Chemical
Society
2015
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Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4887939/ https://www.ncbi.nlm.nih.gov/pubmed/26266698 http://dx.doi.org/10.1021/jacs.5b06648 |
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author | Daifuku, Stephanie L. Kneebone, Jared L. Snyder, Benjamin E. R. Neidig, Michael L. |
author_facet | Daifuku, Stephanie L. Kneebone, Jared L. Snyder, Benjamin E. R. Neidig, Michael L. |
author_sort | Daifuku, Stephanie L. |
collection | PubMed |
description | [Image: see text] While previous studies have identified FeMes(2)(SciOPP) as the active catalyst species in iron–SciOPP catalyzed Kumada cross-coupling of mesitylmagnesium bromide and primary alkyl halides, the active catalyst species in cross-couplings with phenyl nucleophiles, where low valent iron species might be prevalent due to accessible reductive elimination pathways, remains undefined. In the present study, in situ Mössbauer and magnetic circular dichroism spectroscopic studies combined with inorganic syntheses and reaction studies are employed to evaluate the in situ formed iron species and identify the active catalytic species in iron–SciOPP catalyzed Suzuki–Miyaura and Kumada cross-couplings of phenyl nucleophiles and secondary alkyl halides. While reductive elimination to form Fe(η(6)-biphenyl)(SciOPP) occurs upon reaction of FeCl(2)(SciOPP) with phenyl nucleophiles, this iron(0) species is not found to be kinetically competent for catalysis. Importantly, mono- and bis-phenylated iron(II)–SciOPP species that form prior to reductive elimination are identified, where both species are found to be reactive toward electrophile at catalytically relevant rates. The higher selectivity toward the formation of cross-coupled product observed for the monophenylated species combined with the undertransmetalated nature of the in situ iron species in both Kumada and Suzuki–Miyaura reactions indicates that Fe(Ph)X(SciOPP) (X = Br, Cl) is the predominant reactive species in cross-coupling. Overall, these studies demonstrate that low-valent iron is not required for the generation of highly reactive species for effective aryl-alkyl cross-couplings. |
format | Online Article Text |
id | pubmed-4887939 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2015 |
publisher | American Chemical
Society |
record_format | MEDLINE/PubMed |
spelling | pubmed-48879392016-06-02 Iron(II) Active Species in Iron–Bisphosphine Catalyzed Kumada and Suzuki–Miyaura Cross-Couplings of Phenyl Nucleophiles and Secondary Alkyl Halides Daifuku, Stephanie L. Kneebone, Jared L. Snyder, Benjamin E. R. Neidig, Michael L. J Am Chem Soc [Image: see text] While previous studies have identified FeMes(2)(SciOPP) as the active catalyst species in iron–SciOPP catalyzed Kumada cross-coupling of mesitylmagnesium bromide and primary alkyl halides, the active catalyst species in cross-couplings with phenyl nucleophiles, where low valent iron species might be prevalent due to accessible reductive elimination pathways, remains undefined. In the present study, in situ Mössbauer and magnetic circular dichroism spectroscopic studies combined with inorganic syntheses and reaction studies are employed to evaluate the in situ formed iron species and identify the active catalytic species in iron–SciOPP catalyzed Suzuki–Miyaura and Kumada cross-couplings of phenyl nucleophiles and secondary alkyl halides. While reductive elimination to form Fe(η(6)-biphenyl)(SciOPP) occurs upon reaction of FeCl(2)(SciOPP) with phenyl nucleophiles, this iron(0) species is not found to be kinetically competent for catalysis. Importantly, mono- and bis-phenylated iron(II)–SciOPP species that form prior to reductive elimination are identified, where both species are found to be reactive toward electrophile at catalytically relevant rates. The higher selectivity toward the formation of cross-coupled product observed for the monophenylated species combined with the undertransmetalated nature of the in situ iron species in both Kumada and Suzuki–Miyaura reactions indicates that Fe(Ph)X(SciOPP) (X = Br, Cl) is the predominant reactive species in cross-coupling. Overall, these studies demonstrate that low-valent iron is not required for the generation of highly reactive species for effective aryl-alkyl cross-couplings. American Chemical Society 2015-08-12 2015-09-09 /pmc/articles/PMC4887939/ /pubmed/26266698 http://dx.doi.org/10.1021/jacs.5b06648 Text en Copyright © 2015 American Chemical Society This is an open access article published under an ACS AuthorChoice License (http://pubs.acs.org/page/policy/authorchoice_termsofuse.html) , which permits copying and redistribution of the article or any adaptations for non-commercial purposes. |
spellingShingle | Daifuku, Stephanie L. Kneebone, Jared L. Snyder, Benjamin E. R. Neidig, Michael L. Iron(II) Active Species in Iron–Bisphosphine Catalyzed Kumada and Suzuki–Miyaura Cross-Couplings of Phenyl Nucleophiles and Secondary Alkyl Halides |
title | Iron(II)
Active Species in Iron–Bisphosphine
Catalyzed Kumada and Suzuki–Miyaura Cross-Couplings of Phenyl
Nucleophiles and Secondary Alkyl Halides |
title_full | Iron(II)
Active Species in Iron–Bisphosphine
Catalyzed Kumada and Suzuki–Miyaura Cross-Couplings of Phenyl
Nucleophiles and Secondary Alkyl Halides |
title_fullStr | Iron(II)
Active Species in Iron–Bisphosphine
Catalyzed Kumada and Suzuki–Miyaura Cross-Couplings of Phenyl
Nucleophiles and Secondary Alkyl Halides |
title_full_unstemmed | Iron(II)
Active Species in Iron–Bisphosphine
Catalyzed Kumada and Suzuki–Miyaura Cross-Couplings of Phenyl
Nucleophiles and Secondary Alkyl Halides |
title_short | Iron(II)
Active Species in Iron–Bisphosphine
Catalyzed Kumada and Suzuki–Miyaura Cross-Couplings of Phenyl
Nucleophiles and Secondary Alkyl Halides |
title_sort | iron(ii)
active species in iron–bisphosphine
catalyzed kumada and suzuki–miyaura cross-couplings of phenyl
nucleophiles and secondary alkyl halides |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4887939/ https://www.ncbi.nlm.nih.gov/pubmed/26266698 http://dx.doi.org/10.1021/jacs.5b06648 |
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