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Base-Promoted Homolytic Aromatic Substitution (BHAS) Reactions and Hydrodehalogenations Driven by Green Light and an Iron(III)-NHC Photoredox Catalyst

de Groot, Lisa H.M. LU ; García-Mateos, Clara LU orcid ; Johnson, Catherine E. ; Freyr Hlynsson, Valtýr LU ; Sharma, Alpesh K. LU ; Lomoth, Reiner and Wärnmark, Kenneth LU (2025) In Chemistry - A European Journal 31(21).
Abstract

An Fe(III)-NHC complex has been employed for the green light driven catalysis of base-promoted homolytic aromatic substitution (BHAS) reactions. Tributylamine was used as a sacrificial electron donor, together with potassium carbonate as base in dimethyl sulfoxide as solvent. In contrast to previously studied photocatalysts, the excited Fe(III)-NHC complex is not reducing the arylhalide substrates. Instead, the latter are activated by α-aminoalkyl radicals formed upon reductive quenching of the photocatalyst by tributylamine. Avoiding strongly reducing photocatalysts as well as strong base, these mild reaction conditions allowed for the expansion of the substrate scope to accommodate also aldehyde and ester substituents. 100 %... (More)

An Fe(III)-NHC complex has been employed for the green light driven catalysis of base-promoted homolytic aromatic substitution (BHAS) reactions. Tributylamine was used as a sacrificial electron donor, together with potassium carbonate as base in dimethyl sulfoxide as solvent. In contrast to previously studied photocatalysts, the excited Fe(III)-NHC complex is not reducing the arylhalide substrates. Instead, the latter are activated by α-aminoalkyl radicals formed upon reductive quenching of the photocatalyst by tributylamine. Avoiding strongly reducing photocatalysts as well as strong base, these mild reaction conditions allowed for the expansion of the substrate scope to accommodate also aldehyde and ester substituents. 100 % conversion was obtained after 48 h of irradiation. In this way a wide variety of cyclized products and their corresponding hydrodehalogenated products were obtained as isolated and pure compounds, in the vast majority of cases.

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author
; ; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
BHAS, Green light, Iron, NHC ligand, Photoredox catalysis
in
Chemistry - A European Journal
volume
31
issue
21
article number
e202500409
publisher
Wiley-Blackwell
external identifiers
  • scopus:105002269994
  • pmid:39981893
ISSN
0947-6539
DOI
10.1002/chem.202500409
language
English
LU publication?
yes
id
8affd6dc-f032-493c-a4ef-09501c50ac6b
date added to LUP
2025-08-08 09:19:01
date last changed
2025-08-09 03:00:08
@article{8affd6dc-f032-493c-a4ef-09501c50ac6b,
  abstract     = {{<p>An Fe(III)-NHC complex has been employed for the green light driven catalysis of base-promoted homolytic aromatic substitution (BHAS) reactions. Tributylamine was used as a sacrificial electron donor, together with potassium carbonate as base in dimethyl sulfoxide as solvent. In contrast to previously studied photocatalysts, the excited Fe(III)-NHC complex is not reducing the arylhalide substrates. Instead, the latter are activated by α-aminoalkyl radicals formed upon reductive quenching of the photocatalyst by tributylamine. Avoiding strongly reducing photocatalysts as well as strong base, these mild reaction conditions allowed for the expansion of the substrate scope to accommodate also aldehyde and ester substituents. 100 % conversion was obtained after 48 h of irradiation. In this way a wide variety of cyclized products and their corresponding hydrodehalogenated products were obtained as isolated and pure compounds, in the vast majority of cases.</p>}},
  author       = {{de Groot, Lisa H.M. and García-Mateos, Clara and Johnson, Catherine E. and Freyr Hlynsson, Valtýr and Sharma, Alpesh K. and Lomoth, Reiner and Wärnmark, Kenneth}},
  issn         = {{0947-6539}},
  keywords     = {{BHAS; Green light; Iron; NHC ligand; Photoredox catalysis}},
  language     = {{eng}},
  number       = {{21}},
  publisher    = {{Wiley-Blackwell}},
  series       = {{Chemistry - A European Journal}},
  title        = {{Base-Promoted Homolytic Aromatic Substitution (BHAS) Reactions and Hydrodehalogenations Driven by Green Light and an Iron(III)-NHC Photoredox Catalyst}},
  url          = {{http://dx.doi.org/10.1002/chem.202500409}},
  doi          = {{10.1002/chem.202500409}},
  volume       = {{31}},
  year         = {{2025}},
}