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Palladium‐Catalyzed C(sp(3))−H Arylation of Primary Amines Using a Catalytic Alkyl Acetal to Form a Transient Directing Group

C−H Functionalization of amines is a prominent challenge due to the strong complexation of amines to transition metal catalysts, and therefore typically requires derivatization at nitrogen with a directing group. Transient directing groups (TDGs) permit C−H functionalization in a single operation, w...

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Autores principales: St John‐Campbell, Sahra, Ou, Alex K., Bull, James A.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: John Wiley and Sons Inc. 2018
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6391947/
https://www.ncbi.nlm.nih.gov/pubmed/30255961
http://dx.doi.org/10.1002/chem.201804515
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author St John‐Campbell, Sahra
Ou, Alex K.
Bull, James A.
author_facet St John‐Campbell, Sahra
Ou, Alex K.
Bull, James A.
author_sort St John‐Campbell, Sahra
collection PubMed
description C−H Functionalization of amines is a prominent challenge due to the strong complexation of amines to transition metal catalysts, and therefore typically requires derivatization at nitrogen with a directing group. Transient directing groups (TDGs) permit C−H functionalization in a single operation, without needing these additional steps for directing group installation and removal. Here we report a palladium catalyzed γ‐C−H arylation of amines using catalytic amounts of alkyl acetals as transient activators (e.g. commercially available (2,2‐dimethoxyethoxy)benzene). This simple additive enables arylation of amines with a wide range of aryl iodides. Key structural features of the novel TDG are examined, demonstrating an important role for the masked carbonyl and ether functionalities. Detailed kinetic (RPKA) and mechanistic investigations determine the order in all reagents, and identify cyclopalladation as the turnover limiting step. Finally, the discovery of an unprecedented off‐cycle free‐amine directed ϵ‐cyclopalladation of the arylation product is reported.
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spelling pubmed-63919472019-03-07 Palladium‐Catalyzed C(sp(3))−H Arylation of Primary Amines Using a Catalytic Alkyl Acetal to Form a Transient Directing Group St John‐Campbell, Sahra Ou, Alex K. Bull, James A. Chemistry Full Papers C−H Functionalization of amines is a prominent challenge due to the strong complexation of amines to transition metal catalysts, and therefore typically requires derivatization at nitrogen with a directing group. Transient directing groups (TDGs) permit C−H functionalization in a single operation, without needing these additional steps for directing group installation and removal. Here we report a palladium catalyzed γ‐C−H arylation of amines using catalytic amounts of alkyl acetals as transient activators (e.g. commercially available (2,2‐dimethoxyethoxy)benzene). This simple additive enables arylation of amines with a wide range of aryl iodides. Key structural features of the novel TDG are examined, demonstrating an important role for the masked carbonyl and ether functionalities. Detailed kinetic (RPKA) and mechanistic investigations determine the order in all reagents, and identify cyclopalladation as the turnover limiting step. Finally, the discovery of an unprecedented off‐cycle free‐amine directed ϵ‐cyclopalladation of the arylation product is reported. John Wiley and Sons Inc. 2018-11-08 2018-12-03 /pmc/articles/PMC6391947/ /pubmed/30255961 http://dx.doi.org/10.1002/chem.201804515 Text en © 2018 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of the http://creativecommons.org/licenses/by/4.0/ License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
spellingShingle Full Papers
St John‐Campbell, Sahra
Ou, Alex K.
Bull, James A.
Palladium‐Catalyzed C(sp(3))−H Arylation of Primary Amines Using a Catalytic Alkyl Acetal to Form a Transient Directing Group
title Palladium‐Catalyzed C(sp(3))−H Arylation of Primary Amines Using a Catalytic Alkyl Acetal to Form a Transient Directing Group
title_full Palladium‐Catalyzed C(sp(3))−H Arylation of Primary Amines Using a Catalytic Alkyl Acetal to Form a Transient Directing Group
title_fullStr Palladium‐Catalyzed C(sp(3))−H Arylation of Primary Amines Using a Catalytic Alkyl Acetal to Form a Transient Directing Group
title_full_unstemmed Palladium‐Catalyzed C(sp(3))−H Arylation of Primary Amines Using a Catalytic Alkyl Acetal to Form a Transient Directing Group
title_short Palladium‐Catalyzed C(sp(3))−H Arylation of Primary Amines Using a Catalytic Alkyl Acetal to Form a Transient Directing Group
title_sort palladium‐catalyzed c(sp(3))−h arylation of primary amines using a catalytic alkyl acetal to form a transient directing group
topic Full Papers
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6391947/
https://www.ncbi.nlm.nih.gov/pubmed/30255961
http://dx.doi.org/10.1002/chem.201804515
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