Visible-Light-Mediated Organocatalyzed Thiol–Ene Reaction Initiated by a Proton-Coupled Electron Transfer

2019 ◽  
Vol 84 (12) ◽  
pp. 8337-8343 ◽  
Author(s):  
Vitalij V. Levin ◽  
Alexander D. Dilman
Keyword(s):  
Electron Transfer ◽  
Visible Light ◽  
Ene Reaction ◽  
Proton Coupled Electron Transfer

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>

Asymmetric alkylation of remote C(sp3)–H bonds by combining proton-coupled electron transfer with chiral Lewis acid catalysis

2017 ◽  
Vol 53 (64) ◽  
pp. 8964-8967 ◽  
Author(s):  
Wei Yuan ◽  
Zijun Zhou ◽  
Lei Gong ◽  
Eric Meggers
Keyword(s):  
Electron Transfer ◽  
Hydrogen Atom ◽  
Visible Light ◽  
Lewis Acid ◽  
Acid Catalysis ◽  
Hydrogen Atom Transfer ◽  
Lewis Acid Catalysis ◽  
Asymmetric Alkylation ◽  
Proton Coupled Electron Transfer ◽  
Chiral Lewis Acid

The catalytic asymmetric alkylation of the remote, unactivated δ-position of N-alkyl amides was enabled by the combination of visible-light-induced proton-coupled electron transfer, 1,5-hydrogen atom transfer, and chiral Lewis acid catalysis.

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 Evaluation of excited state bond weakening for ammonia synthesis from a manganese nitride: stepwise proton coupled electron transfer is preferred over hydrogen atom transfer

2019 ◽  
Vol 55 (39) ◽  
pp. 5595-5598 ◽  
Author(s):  
Florian Loose ◽  
Dian Wang ◽  
Lei Tian ◽  
Gregory D. Scholes ◽  
Robert R. Knowles ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Excited State ◽  
Hydrogen Atom ◽  
Visible Light ◽  
Driving Force ◽  
Ammonia Synthesis ◽  
Hydrogen Atom Transfer ◽  
Atom Transfer ◽  
Proton Coupled Electron Transfer ◽  
Manganese Nitride

Concepts for the thermodynamically challenging synthesis of weak N–H bonds by photoinduced proton coupled electron transfer are explored. By harvesting visible light as driving force, ammonia synthesis was achieved and mechanistically elucidated.

Photoanodes for water oxidation with visible light based on a pentacyclic quinoid organic dye enabling proton-coupled electron transfer

2020 ◽  
Vol 56 (15) ◽  
pp. 2248-2251
Author(s):  
Giulia Alice Volpato ◽  
Martina Marasi ◽  
Thomas Gobbato ◽  
Francesca Valentini ◽  
Federica Sabuzi ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Visible Light ◽  
Water Oxidation ◽  
Visible Region ◽  
Organic Dye ◽  
Proton Coupled Electron Transfer

A novel pentacyclic quinoid photosensitizer with extended absorption in the visible region and enabling proton-coupled electron transfer is employed in photoelectrodes for water oxidation in combination with a ruthenium polyoxometalate catalyst.

scholarly journals Enantioselective catalytic β-amination through proton-coupled electron transfer followed by stereocontrolled radical–radical coupling

2017 ◽  
Vol 8 (8) ◽  
pp. 5757-5763 ◽  
Author(s):  
Zijun Zhou ◽  
Yanjun Li ◽  
Bowen Han ◽  
Lei Gong ◽  
Eric Meggers
Keyword(s):  
Electron Transfer ◽  
Visible Light ◽  
Conjugate Addition ◽  
Radical Coupling ◽  
Proton Coupled Electron Transfer

The catalytic asymmetry conjugate addition of carbamates to α,β-unsaturated 2-acyl imidazoles is accomplished using visible-light-induced proton-coupled electron transfer.

Photocatalytic intermolecular anti-Markovnikov hydroamination of unactivated alkenes with N-hydroxyphthalimide

2021 ◽  
Author(s):  
Zhi-Peng Ye ◽  
Yuan-Zhuo Hu ◽  
Peng-Ju Xia ◽  
Hao-Yue Xiang ◽  
Kai Chen ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Visible Light ◽  
Proton Coupled Electron Transfer

A visible-light-induced/phosphite-promoted anti-Markovnikov hydroamination of alkenes with N-hydroxyphthalimide was successfully realized, which was initiated by a proton-coupled electron transfer to enable direct cleavage of its N–O bond.

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