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Nickel-Catalyzed Negishi Arylations of Propargylic Bromides: A Mechanistic Investigation
[Image: see text] Although nickel-catalyzed stereoconvergent couplings of racemic alkyl electrophiles are emerging as a powerful tool in organic chemistry, to date there have been no systematic mechanistic studies of such processes. Herein, we examine the pathway for enantioselective Negishi arylati...
Autores principales: | , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
American Chemical
Society
2014
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Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4277758/ https://www.ncbi.nlm.nih.gov/pubmed/25402209 http://dx.doi.org/10.1021/ja508718m |
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author | Schley, Nathan D. Fu, Gregory C. |
author_facet | Schley, Nathan D. Fu, Gregory C. |
author_sort | Schley, Nathan D. |
collection | PubMed |
description | [Image: see text] Although nickel-catalyzed stereoconvergent couplings of racemic alkyl electrophiles are emerging as a powerful tool in organic chemistry, to date there have been no systematic mechanistic studies of such processes. Herein, we examine the pathway for enantioselective Negishi arylations of secondary propargylic bromides, and we provide evidence for an unanticipated radical chain pathway wherein oxidative addition of the C–Br bond occurs through a bimetallic mechanism. In particular, we have crystallographically characterized a diamagnetic arylnickel(II) complex, [(i-Pr-pybox)Ni(II)Ph]BAr(F)(4), and furnished support for [(i-Pr-pybox)Ni(II)Ph](+) being the predominant nickel-containing species formed under the catalyzed conditions as well as a key player in the cross-coupling mechanism. On the other hand, our observations do not require a role for an organonickel(I) intermediate (e.g., (i-Pr-pybox)Ni(I)Ph), which has previously been suggested to be an intermediate in nickel-catalyzed cross-couplings, oxidatively adding alkyl electrophiles through a monometallic pathway. |
format | Online Article Text |
id | pubmed-4277758 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2014 |
publisher | American Chemical
Society |
record_format | MEDLINE/PubMed |
spelling | pubmed-42777582015-11-17 Nickel-Catalyzed Negishi Arylations of Propargylic Bromides: A Mechanistic Investigation Schley, Nathan D. Fu, Gregory C. J Am Chem Soc [Image: see text] Although nickel-catalyzed stereoconvergent couplings of racemic alkyl electrophiles are emerging as a powerful tool in organic chemistry, to date there have been no systematic mechanistic studies of such processes. Herein, we examine the pathway for enantioselective Negishi arylations of secondary propargylic bromides, and we provide evidence for an unanticipated radical chain pathway wherein oxidative addition of the C–Br bond occurs through a bimetallic mechanism. In particular, we have crystallographically characterized a diamagnetic arylnickel(II) complex, [(i-Pr-pybox)Ni(II)Ph]BAr(F)(4), and furnished support for [(i-Pr-pybox)Ni(II)Ph](+) being the predominant nickel-containing species formed under the catalyzed conditions as well as a key player in the cross-coupling mechanism. On the other hand, our observations do not require a role for an organonickel(I) intermediate (e.g., (i-Pr-pybox)Ni(I)Ph), which has previously been suggested to be an intermediate in nickel-catalyzed cross-couplings, oxidatively adding alkyl electrophiles through a monometallic pathway. American Chemical Society 2014-11-17 2014-11-26 /pmc/articles/PMC4277758/ /pubmed/25402209 http://dx.doi.org/10.1021/ja508718m Text en Copyright © 2014 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 | Schley, Nathan D. Fu, Gregory C. Nickel-Catalyzed Negishi Arylations of Propargylic Bromides: A Mechanistic Investigation |
title | Nickel-Catalyzed
Negishi Arylations of Propargylic
Bromides: A Mechanistic Investigation |
title_full | Nickel-Catalyzed
Negishi Arylations of Propargylic
Bromides: A Mechanistic Investigation |
title_fullStr | Nickel-Catalyzed
Negishi Arylations of Propargylic
Bromides: A Mechanistic Investigation |
title_full_unstemmed | Nickel-Catalyzed
Negishi Arylations of Propargylic
Bromides: A Mechanistic Investigation |
title_short | Nickel-Catalyzed
Negishi Arylations of Propargylic
Bromides: A Mechanistic Investigation |
title_sort | nickel-catalyzed
negishi arylations of propargylic
bromides: a mechanistic investigation |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4277758/ https://www.ncbi.nlm.nih.gov/pubmed/25402209 http://dx.doi.org/10.1021/ja508718m |
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