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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Recent advances in visible light-activated radical coupling reactions triggered by (i) ruthenium, (ii) iridium and (iii) organic photoredox agents

Chemical Society Reviews, Journal Year: 2021, Volume and Issue: 50(17), P. 9540 - 9685

Published: Jan. 1, 2021

Visible light-activated reactions continue to expand and diversify. The example shown here is a Birch reduction achieved by organophotoredox reagents.

Language: Английский

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Visible-light induced dearomatization reactions

Chemical Society Reviews, Journal Year: 2022, Volume and Issue: 51(6), P. 2145 - 2170

Published: Jan. 1, 2022

This review provides an overview of visible-light induced dearomatization reactions classified based on the manner in which aromaticity is disrupted.

Language: Английский

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Non-innocent Radical Ion Intermediates in Photoredox Catalysis: Parallel Reduction Modes Enable Coupling of Diverse Aryl Chlorides

Journal of the American Chemical Society, Journal Year: 2021, Volume and Issue: 143(29), P. 10882 - 10889

Published: July 13, 2021

We describe a photocatalytic system that elicits potent photoreductant activity from conventional photocatalysts by leveraging radical anion intermediates generated in situ. The combination of an isophthalonitrile photocatalyst and sodium formate promotes diverse aryl coupling reactions abundant but difficult to reduce chloride substrates. Mechanistic studies reveal two parallel pathways for substrate reduction both enabled key terminal reductant byproduct, carbon dioxide anion.

Language: Английский

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Unveiling Extreme Photoreduction Potentials of Donor–Acceptor Cyanoarenes to Access Aryl Radicals from Aryl Chlorides

Journal of the American Chemical Society, Journal Year: 2021, Volume and Issue: 143(33), P. 13266 - 13273

Published: Aug. 16, 2021

Since the seminal work of Zhang in 2016, donor–acceptor cyanoarene-based fluorophores, such as 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN), have been widely applied photoredox catalysis and used excellent metal-free alternatives to noble metal Ir- Ru-based photocatalysts. However, all reported reactions involving this chromophore family are based on harnessing energy from a single visible light photon, with limited range redox potentials −1.92 +1.79 V vs SCE. Here, we document unprecedented discovery that fluorophores can undergo consecutive photoinduced electron transfer (ConPET) achieve very high reduction potentials. One newly synthesized catalysts, 2,4,5-tri(9H-carbazol-9-yl)-6-(ethyl(phenyl)amino)isophthalonitrile (3CzEPAIPN), possesses long-lived (12.95 ns) excited radical anion form, 3CzEPAIPN•–*, which be activate reductively recalcitrant aryl chlorides (Ered ≈ −1.9 −2.9 SCE) under mild conditions. The resultant radicals engaged synthetically valuable aromatic C–B, C–P, C–C bond formation furnish arylboronates, arylphosphonium salts, arylphosphonates, spirocyclic cyclohexadienes.

Language: Английский

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Synthetic Molecular Photoelectrochemistry: New Frontiers in Synthetic Applications, Mechanistic Insights and Scalability

Angewandte Chemie International Edition, Journal Year: 2021, Volume and Issue: 61(12)

Published: Sept. 3, 2021

Synthetic photoelectrochemistry (PEC) is receiving increasing attention as a new frontier for the generation and handling of reactive intermediates. PEC permits selective single-electron transfer (SET) reactions in much greener way broadens redox window possible transformations. Herein, most recent contributions are reviewed, demonstrating exciting opportunities, namely, combination with other reactivity paradigms (hydrogen-atom transfer, radical polar crossover, energy sensitization), scalability up to multigram scale, novel selectivities SET super-oxidations/reductions importance precomplexation temporally enable excited ion catalysis.

Language: Английский

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Visible-light photocatalytic di- and hydro-carboxylation of unactivated alkenes with CO2

Nature Catalysis, Journal Year: 2022, Volume and Issue: 5(9), P. 832 - 838

Published: Sept. 15, 2022

Language: Английский

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Emerging concepts in photocatalytic organic synthesis

iScience, Journal Year: 2021, Volume and Issue: 24(3), P. 102209 - 102209

Published: Feb. 21, 2021

Visible light photocatalysis has become a powerful tool in organic synthesis that uses photons as traceless, sustainable reagents. Most of the activities field focus on development new reactions via common photoredox cycles, but recently number exciting concepts and strategies entered less charted territories. We survey approaches enable use longer wavelengths show wavelength intensity are import parameters tuning reactivity photocatalyst to control or change selectivity chemical reactions. In addition, we discuss recent efforts substitute strong reductants, such elemental lithium sodium, by technological advances field.

Language: Английский

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Hole-mediated photoredox catalysis: tris(p-substituted)biarylaminium radical cations as tunable, precomplexing and potent photooxidants

Organic Chemistry Frontiers, Journal Year: 2021, Volume and Issue: 8(6), P. 1132 - 1142

Published: Jan. 1, 2021

Triarylamines are demonstrated as novel, tunable electroactivated photocatalysts that use dispersion precomplexation to harness the full potential of visible photon (>4.0 V vs. SCE) in anti-Kasha photo(electro)chemical super-oxidations arenes.

Language: Английский

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Chemoselective (Hetero)Arene Electroreduction Enabled by Rapid Alternating Polarity

Journal of the American Chemical Society, Journal Year: 2022, Volume and Issue: 144(13), P. 5762 - 5768

Published: March 29, 2022

Conventional chemical and even electrochemical Birch-type reductions suffer from a lack of chemoselectivity due to reliance on alkali metals or harshly reducing conditions. This study reveals that simpler avenue is available for such by simply altering the waveform current delivery, namely rapid alternating polarity (rAP). The developed method solves these issues, proceeding in protic solvent, can be easily scaled up without any metal additives stringently anhydrous

Language: Английский

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