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Cathodic radical cyclisation of aryl halides using a strongly-reducing catalytic mediator in flow

Cathodic radical cyclisation of aryl halides using a strongly-reducing catalytic mediator in flow
Cathodic radical cyclisation of aryl halides using a strongly-reducing catalytic mediator in flow

Electro-reductive radical cyclisation of aryl halides affords the corresponding hetero- and carbo-cycles in an undivided flow reactor equipped with steel and carbon electrodes using an organic mediator. A dissolving metal anode is not needed, and the mediator can be employed in a sub-stoichiometric amount (0.05 equiv), increasing the practical utility of cathodic radical cyclisation. The methodology is applied to O-, N-, and C-tethers, yielding tricyclic fused and spiro systems. In the absence of mediator, the major pathway is hydrogenolysis of the C−X bond, a 2 e process occurring at the cathode. Predominance of the radical pathway in presence of a strongly reducing mediator (M) is consistent with homogeneous electron-transfer in a reaction layer detached from the cathode surface, where the flux of M .− leaving the electrode is such that little aryl halide reaches the cathode.

Electrosynthesis, Flow Chemistry, Mediator, Radical Cyclization, Reductive Cyclization
1433-7851
Folgueiras Amador, Ana
080c345d-0a05-406a-bf7c-1939ca9c0aaa
Teuten, Alexander
9ac179e7-8ced-4509-8c18-7d32d80afbdb
Salam Perez, Mateo
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Pearce, James
c8389bad-182d-4ac6-8af0-52fb40b9bb95
Denuault, Guy
5c76e69f-e04e-4be5-83c5-e729887ffd4e
Pletcher, Derek
f22ebe69-b859-4a89-80b0-9e190e6f8f30
Parsons, Phillip James
fae8e111-ea34-4def-abd9-5d43d8077173
Harrowven, David C.
bddcfab6-dbde-49df-aec2-42abbcf5d10b
Brown, Richard C.D.
21ce697a-7c3a-480e-919f-429a3d8550f5
Folgueiras Amador, Ana
080c345d-0a05-406a-bf7c-1939ca9c0aaa
Teuten, Alexander
9ac179e7-8ced-4509-8c18-7d32d80afbdb
Salam Perez, Mateo
fbc16b78-7ab5-4d63-ada5-20e67d5d6c4e
Pearce, James
c8389bad-182d-4ac6-8af0-52fb40b9bb95
Denuault, Guy
5c76e69f-e04e-4be5-83c5-e729887ffd4e
Pletcher, Derek
f22ebe69-b859-4a89-80b0-9e190e6f8f30
Parsons, Phillip James
fae8e111-ea34-4def-abd9-5d43d8077173
Harrowven, David C.
bddcfab6-dbde-49df-aec2-42abbcf5d10b
Brown, Richard C.D.
21ce697a-7c3a-480e-919f-429a3d8550f5

Folgueiras Amador, Ana, Teuten, Alexander, Salam Perez, Mateo, Pearce, James, Denuault, Guy, Pletcher, Derek, Parsons, Phillip James, Harrowven, David C. and Brown, Richard C.D. (2022) Cathodic radical cyclisation of aryl halides using a strongly-reducing catalytic mediator in flow. Angewandte Chemie International Edition, 61 (35), [e202203694]. (doi:10.1002/anie.202203694).

Record type: Article

Abstract

Electro-reductive radical cyclisation of aryl halides affords the corresponding hetero- and carbo-cycles in an undivided flow reactor equipped with steel and carbon electrodes using an organic mediator. A dissolving metal anode is not needed, and the mediator can be employed in a sub-stoichiometric amount (0.05 equiv), increasing the practical utility of cathodic radical cyclisation. The methodology is applied to O-, N-, and C-tethers, yielding tricyclic fused and spiro systems. In the absence of mediator, the major pathway is hydrogenolysis of the C−X bond, a 2 e process occurring at the cathode. Predominance of the radical pathway in presence of a strongly reducing mediator (M) is consistent with homogeneous electron-transfer in a reaction layer detached from the cathode surface, where the flux of M .− leaving the electrode is such that little aryl halide reaches the cathode.

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Angew Chem Int Ed - 2022 - Folgueiras‐Amador - Cathodic Radical Cyclisation of Aryl Halides Using a Strongly‐Reducing - Version of Record
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Accepted/In Press date: 4 July 2022
e-pub ahead of print date: 5 July 2022
Published date: 26 August 2022
Additional Information: The authors acknowledge financial support from the ERDF (LabFact: InterReg V project 121), EPSRC (Photo-Electro Programme Grant EP/P013341/1 and EP/K039466/1), and Johnson Matthey (iCASE MSP). © 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.
Keywords: Electrosynthesis, Flow Chemistry, Mediator, Radical Cyclization, Reductive Cyclization

Identifiers

Local EPrints ID: 468316
URI: http://eprints.soton.ac.uk/id/eprint/468316
ISSN: 1433-7851
PURE UUID: f8e0280c-f676-492a-bc07-6d64e16b3c01
ORCID for James Pearce: ORCID iD orcid.org/0000-0002-8401-2417
ORCID for Guy Denuault: ORCID iD orcid.org/0000-0002-8630-9492
ORCID for David C. Harrowven: ORCID iD orcid.org/0000-0001-6730-3573
ORCID for Richard C.D. Brown: ORCID iD orcid.org/0000-0003-0156-7087

Catalogue record

Date deposited: 10 Aug 2022 16:35
Last modified: 17 Mar 2024 02:44

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Contributors

Author: Ana Folgueiras Amador
Author: Alexander Teuten
Author: Mateo Salam Perez
Author: James Pearce ORCID iD
Author: Guy Denuault ORCID iD
Author: Derek Pletcher
Author: Phillip James Parsons

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