Catalytic Hydroetherification of Unactivated Alkenes Enabled by Proton‐Coupled Electron Transfer

We report a catalytic, light‐driven method for the intramolecular hydroetherification of unactivated alkenols to furnish cyclic ether products. These reactions occur under visible‐light irradiation in the presence of an IrIII‐based photoredox catalyst, a Brønsted base catalyst, and a hydrogen‐atom t...

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Bibliographic Details
Published in:Angewandte Chemie 2020-07, Vol.132 (29), p.11943-11947
Main Authors: Tsui, Elaine, Metrano, Anthony J., Tsuchiya, Yuto, Knowles, Robert R.
Format: Article
Language:English
Subjects:
alcohols
Alkenes
Catalysts
Chemistry
Electron transfer
ethers
hydroetherification
Intermediates
Irradiation
Light irradiation
photocatalysis
Protons
Radiation
radicals
Substrates
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Summary:We report a catalytic, light‐driven method for the intramolecular hydroetherification of unactivated alkenols to furnish cyclic ether products. These reactions occur under visible‐light irradiation in the presence of an IrIII‐based photoredox catalyst, a Brønsted base catalyst, and a hydrogen‐atom transfer (HAT) co‐catalyst. Reactive alkoxy radicals are proposed as key intermediates, generated by direct homolytic activation of alcohol O−H bonds through a proton‐coupled electron‐transfer mechanism. This method exhibits a broad substrate scope and high functional‐group tolerance, and it accommodates a diverse range of alkene substitution patterns. Results demonstrating the extension of this catalytic system to carboetherification reactions are also presented. Alkoxy radicals generated directly by the activation of alcohol O−H bonds under light‐driven catalytic conditions can be leveraged for the intramolecular hydroetherification of unactivated olefins. This strategy enables productive C−O bond formation from highly reactive alkoxy radical intermediates and accommodates a broad substrate scope with high functional‐group tolerance. PCET=proton‐coupled electron transfer, HAT=hydrogen‐atom transfer.
ISSN:0044-8249
1521-3757
DOI:10.1002/ange.202003959