Photons or Electrons? A Critical Comparison of Electrochemistry and Photoredox Catalysis for Organic Synthesis

Chemical Reviews, Journal Year: 2021, Volume and Issue: 122(2), P. 2487 - 2649

Published: Nov. 9, 2021

Redox processes are at the heart of synthetic methods that rely on either electrochemistry or photoredox catalysis, but how do and catalysis compare? Both approaches provide access to high energy intermediates (e.g., radicals) enable bond formations not constrained by rules ionic 2 electron (e) mechanisms. Instead, they 1e mechanisms capable bypassing electronic steric limitations protecting group requirements, thus enabling chemists disconnect molecules in new different ways. However, while providing similar intermediates, differ several physical chemistry principles. Understanding those differences can be key designing transformations forging disconnections. This review aims highlight these similarities between comparing their underlying principles describing impact electrochemical photochemical methods.

Language: Английский

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Photochemical and Electrochemical Applications of Proton-Coupled Electron Transfer in Organic Synthesis

Chemical Reviews, Journal Year: 2021, Volume and Issue: 122(2), P. 2017 - 2291

Published: Nov. 23, 2021

We present here a review of the photochemical and electrochemical applications multi-site proton-coupled electron transfer (MS-PCET) in organic synthesis. MS-PCETs are redox mechanisms which both an proton exchanged together, often concerted elementary step. As such, MS-PCET can function as non-classical mechanism for homolytic bond activation, providing opportunities to generate synthetically useful free radical intermediates directly from wide variety common functional groups. introduction practitioner’s guide reaction design, with emphasis on unique energetic selectivity features that characteristic this class. then chapters oxidative N–H, O–H, S–H, C–H homolysis methods, generation corresponding neutral species. Then, reductive PCET activations involving carbonyl, imine, other X═Y π-systems, heteroarenes, where ketyl, α-amino, heteroarene-derived radicals be generated. Finally, we asymmetric catalysis materials device applications. Within each chapter, subdivide by group undergoing homolysis, thereafter type transformation being promoted. Methods published prior end December 2020 presented.

Language: Английский

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Electro-/photocatalytic alkene-derived radical cation chemistry: recent advances in synthetic applications

Chemical Society Reviews, Journal Year: 2022, Volume and Issue: 51(16), P. 7206 - 7237

Published: Jan. 1, 2022

This review covers the recent progress in electro-/photo-catalytic alkene-derived radical cation chemistry for organic synthesis, including synthetic strategies, plausible mechanisms and further research outlook.

Language: Английский

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Photocatalytic C(sp³) radical generationviaC–H, C–C, and C–X bond cleavage

Chemical Science, Journal Year: 2022, Volume and Issue: 13(19), P. 5465 - 5504

Published: Jan. 1, 2022

C(sp 3 ) radicals (R˙) are of broad research interest and synthetic utility.

Language: Английский

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Metallaphotoredox-enabled aminocarboxylation of alkenes with CO2

Nature Catalysis, Journal Year: 2023, Volume and Issue: 6(10), P. 959 - 968

Published: Sept. 21, 2023

Language: Английский

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Enantioselective Cyanofunctionalization of Aromatic Alkenes via Radical Anions

Journal of the American Chemical Society, Journal Year: 2024, Volume and Issue: 146(2), P. 1410 - 1422

Published: Jan. 5, 2024

Alkene radical ions constitute an integral and unique class of reactive intermediates for the synthesis valuable compounds because they have both unpaired spins charge. However, relatively few synthetic applications alkene anions emerged due to a dearth generally applicable mild anion generation approaches. Precise control over chemo- stereoselectivity in anion-mediated processes represents another long-standing challenge their high reactivity. To overcome these issues, here, we develop new redox-neutral strategy that seamlessly merges photoredox copper catalysis enable controlled orthogonal enantioselective cyanofunctionalization via distonic-like species. This enables highly regio-, chemo-, hydrocyanation, deuterocyanation, cyanocarboxylation alkenes without stoichiometric reductants or oxidants under visible light irradiation. protocol provides blueprint exploration transformation potential anions.

Language: Английский

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Photoredox Activation of Formate Salts: Hydrocarboxylation of Alkenes via Carboxyl Group Transfer

ACS Catalysis, Journal Year: 2021, Volume and Issue: 11(24), P. 15004 - 15012

Published: Dec. 1, 2021

A photoredox activation mode of formate salts for carboxylation was developed. Using a salt as the reductant, carbonyl source, and hydrogen atom transfer reagent, wide range alkenes can be converted into acid products via carboxyl group strategy in an additive-free fashion. Mechanistic studies revealed that radical anion species (CO2•– carbon anions derived from reduction alkenes) are key intermediates transformation. This method has advantages high catalytic efficiency simple system, which may allow this approach to become promising industrial applications.

Language: Английский

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Ketone–Olefin Coupling of Aliphatic and Aromatic Carbonyls Catalyzed by Excited-State Acridine Radicals

Journal of the American Chemical Society, Journal Year: 2022, Volume and Issue: 144(26), P. 11888 - 11896

Published: June 23, 2022

Ketone–olefin coupling reactions are common methods for the formation of carbon–carbon bonds. This reaction class typically requires stoichiometric or super quantities metal reductants, and catalytic variations limited in application. Photoredox catalysis has offered an alternative method toward ketone–olefin reactions, although most scope to easily reducible aromatic carbonyl compounds. Herein, we describe a mild, metal-free using excited-state acridine radical reductant as photoredox catalyst. We demonstrate both intramolecular intermolecular couplings aliphatic ketones aldehydes. Mechanistic evidence is also presented supporting "olefin first" mechanism.

Language: Английский

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Highly reductive photocatalytic systems in organic synthesis

Trends in Chemistry, Journal Year: 2022, Volume and Issue: 4(6), P. 512 - 527

Published: April 27, 2022

Language: Английский

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Understanding Ir(III) Photocatalyst Structure–Activity Relationships: A Highly Parallelized Study of Light-Driven Metal Reduction Processes

Journal of the American Chemical Society, Journal Year: 2022, Volume and Issue: 144(3), P. 1431 - 1444

Published: Jan. 13, 2022

High-throughput synthesis and screening methods were used to measure the photochemical activity of 1440 distinct heteroleptic [Ir(C^N)2(N^N)]+ complexes for photoreduction Sn(II) Zn(II) cations their corresponding neutral metals. Kinetic data collection was carried out using home-built photoreactors measured initial rates, obtained through an automated fitting algorithm, spanned between 0–120 μM/s Sn(0) deposition 0–90 Zn(0) deposition. Photochemical reactivity compared photophysical properties previously such as deaerated excited state lifetime emission spectral these same complexes; however, no clear correlations among features observed. A formal rate law then developed help elucidate observed reactivity. Initial rates found be directly correlated product incident photon flux with three reaction elementary efficiencies: (1) fraction light absorbed by photocatalyst, (2) species that are quenched electron donor, (3) cage escape efficiency. The most active catalysts exhibit high efficiencies all steps, catalyst engineering requirements maximize postulated. kinetic treatment provided mechanistic information needed decipher structure/function trends in high-throughput work.

Language: Английский

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