scholarly journals Chemistry With N-Centered Radicals Generated by Single-Electron Transfer-Oxidation Using Photoredox Catalysis

CCS Chemistry ◽  
2019 ◽  
pp. 38-49 ◽  
Author(s):  
Heng Jiang ◽  
Armido Studer
Keyword(s):  
Electron Transfer ◽  
Recent Literature ◽  
Bond Cleavage ◽  
Photoredox Catalysis ◽  
Proton Coupled Electron Transfer ◽  
Cascade Processes ◽  
Reactive N ◽  
Radical Generation ◽  
Cleavage Reactions ◽  
Oxidative Generation

This review covers the recent literature on oxidative generation of N-centered radicals using photoredox catalysis. The concept of proton-coupled electron transfer is briefly discussed. Applications of such reactive N-centered radicals in cascade processes comprising arene amidation, alkene amidation, C—C bond cleavage reactions, and remote C—H functionalization are addressed. In addition, novel reagents allowing for clean oxidative N-radical generation are discussed.

ChemInform Abstract: Oxygen Switch in Visible-Light Photoredox Catalysis: Radical Additions and Cyclizations and Unexpected C-C-Bond Cleavage Reactions.

ChemInform ◽  
2013 ◽  
Vol 44 (29) ◽  
pp. no-no
Author(s):  
Shaoqun Zhu ◽  
Arindam Das ◽  
Lan Bui ◽  
Hanjun Zhou ◽  
Dennis P. Curran ◽  
...  
Keyword(s):  
Visible Light ◽  
Bond Cleavage ◽  
Photoredox Catalysis ◽  
Cleavage Reactions

scholarly journals Light-Driven Depolymerization of Native Lignin Enabled by Proton- Coupled Electron Transfer

2019 ◽  
Author(s):  
Suong Nguyen ◽  
Phillip Murray ◽  
Robert Knowles
Keyword(s):  
Electron Transfer ◽  
Visible Light ◽  
Bond Cleavage ◽  
Direct Conversion ◽  
Alkoxy Radical ◽  
Radical Intermediate ◽  
Polymer Backbone ◽  
Good Efficiency ◽  
Chemical Reagents ◽  
Proton Coupled Electron Transfer

<div><p>Here we report a catalytic, light-driven method for the redox-neutral depolymerization of native lignin biomass at ambient temperature. This transformation proceeds via a proton-coupled electron-transfer (PCET) activation of an alcohol O–H bond to generate a key alkoxy radical intermediate, which then drives the <i>β</i>-scission of a vicinal C–C bond. Notably, this depolymerization is driven solely by visible light irradiation, requiring no stoichiometric chemical reagents and producing no stoichiometric waste. This method exhibits good efficiency and excellent selectivity for the activation and fragmentation of <i>β</i>-O-4 linkages in the polymer backbone, even in the presence of numerous other PCET-active functional groups. DFT analysis suggests that the key C–C bond cleavage reactions produce non-equilibrium product distributions, driven by excited-state redox events. These results provide further evidence that visible-light photocatalysis can serve as a viable method for the direct conversion of lignin biomass into valuable arene feedstocks.</p></div>

scholarly journals Theoretical Study of C–H Bond Cleavage via Concerted Proton-Coupled Electron Transfer in Fluorenyl-Benzoates

2018 ◽  
Vol 140 (46) ◽  
pp. 15641-15645 ◽  
Author(s):  
Elvira R. Sayfutyarova ◽  
Zachary K. Goldsmith ◽  
Sharon Hammes-Schiffer
Keyword(s):  
Electron Transfer ◽  
Theoretical Study ◽  
Bond Cleavage ◽  
Proton Coupled Electron Transfer

scholarly journals Proton-Coupled Electron Transfer in the Reaction of 3,4-Dihydroxyphenylpyruvic Acid with Reactive Species in Various Media

2015 ◽  
Vol 2015 ◽  
pp. 1-13 ◽  
Author(s):  
J. J. Fifen ◽  
Z. Dhaouadi ◽  
M. Nsangou ◽  
O. Holtomo ◽  
N. Jaidane
Keyword(s):  
Electron Transfer ◽  
Proton Transfer ◽  
Activation Barrier ◽  
Bond Cleavage ◽  
Hydrogen Atom Transfer ◽  
Free Energies ◽  
Solvent Interactions ◽  
Proton Coupled Electron Transfer ◽  
Nonpolar Solvents ◽  
One Step

The distinction of concerted proton-coupled electron transfer (CPCET) from sequential one as well as proton transfer-electron transfer (PT-ET) from electron transfer-proton transfer (ET-PT) in the O–H bond cleavage reactions in various media has always been a difficult task. In this work, the activation barrier of the CPCET mechanism, its rate constants, and reaction free energies related to ET-PT and PT-ET involving coreactive species were presented as good parameters to attempt the problem. DFT calculations were carried out studying the described pathways subsequent to the scavenging of OH• and OBr- by the 3,4-DHPPA in various media. The solvation was described in a hybrid manner using IEF-PCM model conjointly with a model that takes into account some solute-solvent interactions. As a result, we found that the scavenging of hydroxyl radical by 3,4-DHPPA is thermodynamically governed by a one-step hydrogen atom transfer (CPCET) from the acid to the radical in all media. In kinetic viewpoint, CPCET still dominates in the vacuum and in nonpolar solvents, but in polar solvents it could compete strongly with the ET-PT mechanism so that the latter could slightly dominate.

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