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Electrocatalytic Ketyl-Olefin Cyclization at a Favorable Applied Bias Enabled by a Concerted Proton–Electron Transfer Mediator

Derosa, Joseph and Garrido-Barros, Pablo and Peters, Jonas C. (2022) Electrocatalytic Ketyl-Olefin Cyclization at a Favorable Applied Bias Enabled by a Concerted Proton–Electron Transfer Mediator. Inorganic Chemistry, 61 (17). pp. 6672-6678. ISSN 0020-1669. doi:10.1021/acs.inorgchem.2c00839.

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Recent studies showcase reductive concerted proton–electron transfer (CPET) as a powerful strategy for transferring a net hydrogen atom to organic substrates; however, direct application of CPET in the context of C–C bond formation beyond homocoupling is underexplored. We report herein the expansion of electrocatalytic CPET (eCPET) using a Brønsted base-appended cobaltocene mediator ([CpCoCp^(NMe₂)][OTf]) with keto-olefin substrates that undergo cyclization subsequent to ketyl radical generation via eCPET. Using acetophenone-derived substrates with tethered acrylates as radical acceptors, in the presence of tosylic acid, we demonstrate that ketyl-olefin cyclization is achieved by characterization of cis-lactone and alkene products. Mechanistic analysis of this 2 H⁺/2 e⁻ process reveals a mixed order in substrate and acid and a Hammett plot with a modest negative slope, highlighting the contribution of sequential CPET and ET/PT steps involved in the overall rate of the reaction and providing support for initial O–H bond formation. The ability to access ketyl radicals at comparatively mild reduction potentials via controlled potential electrolysis enables functional group tolerance across a range of substrates.

Item Type:Article
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URLURL TypeDescription
Derosa, Joseph0000-0001-8672-4875
Garrido-Barros, Pablo0000-0002-1489-3386
Peters, Jonas C.0000-0002-6610-4414
Additional Information:© 2022 American Chemical Society. Received: March 14, 2022; Published: April 18, 2022. The authors are grateful to the Department of Energy Basic Energy Sciences for support via Grant DE-SC0019136 and the donors of the American Chemical Society Petroleum Research Fund for support. J.D. thanks the Arnold and Mabel Beckman Foundation for a postdoctoral fellowship, and P.G.-B. thanks the Ramón Areces Foundation for a postdoctoral fellowship. J.C.P. acknowledges the Resnick Sustainability Institute for support of laboratory facilities. The authors declare no competing financial interest.
Group:Resnick Sustainability Institute
Funding AgencyGrant Number
Department of Energy (DOE)DE-SC0019136
American Chemical Society Petroleum Research FundUNSPECIFIED
Arnold and Mabel Beckman FoundationUNSPECIFIED
Ramón Areces FoundationUNSPECIFIED
Resnick Sustainability InstituteUNSPECIFIED
Subject Keywords:Ketones, Electrodes, Hydrocarbons, Redox reactions, Cyclization
Issue or Number:17
Record Number:CaltechAUTHORS:20220419-936112000
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Official Citation:Electrocatalytic Ketyl-Olefin Cyclization at a Favorable Applied Bias Enabled by a Concerted Proton–Electron Transfer Mediator. Joseph Derosa, Pablo Garrido-Barros, and Jonas C. Peters. Inorganic Chemistry 2022 61 (17), 6672-6678; DOI: 10.1021/acs.inorgchem.2c00839
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:114382
Deposited By: George Porter
Deposited On:20 Apr 2022 14:16
Last Modified:24 May 2022 21:55

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