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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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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Scaffold hopping by net photochemical carbon deletion of azaarenes

Science, Journal Year: 2022, Volume and Issue: 376(6592), P. 527 - 532

Published: April 28, 2022

Discovery chemists routinely identify purpose-tailored molecules through an iterative structural optimization approach, but the preparation of each successive candidate in a compound series can rarely be conducted manner matching their thought process. This is because many necessary chemical transformations required to modify cores straightforward fashion are not applicable complex contexts. We report method that addresses one facet this problem by allowing hop directly between chemically distinct heteroaromatic scaffolds. Specifically, we show selective photolysis quinoline

Language: Английский

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The advent and development of organophotoredox catalysis

Chemical Communications, Journal Year: 2021, Volume and Issue: 58(9), P. 1263 - 1283

Published: Dec. 10, 2021

We herein discuss how and when organic photocatalysts can efficiently replace or outperform their metal counterparts.

Language: Английский

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Radical relay cyclization/C–C bond formation of allyloxy-tethered aryl iodides with quinoxalin-2(1H)-ones via polysulfide anion photocatalysis

Organic & Biomolecular Chemistry, Journal Year: 2024, Volume and Issue: 22(8), P. 1708 - 1713

Published: Jan. 1, 2024

A visible-light-induced radical relay cyclization/C-C bond formation of quinoxalin-2(1

Language: Английский

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Excited Organic Radicals in Photoredox Catalysis

JACS Au, Journal Year: 2025, Volume and Issue: 5(2), P. 426 - 447

Published: Jan. 29, 2025

Many important synthetic-oriented works have proposed excited organic radicals as photoactive species, yet mechanistic studies raised doubts about whether they can truly function photocatalysts. This skepticism originates from the formation of (photo)redox-active degradation products and picosecond decay electronically radicals, which is considered too short for diffusion-based photoinduced electron transfer reactions. From this perspective, we analyze synthetic transformations where been photocatalysts, comparing their theoretical maximum state potentials with required observed photocatalytic reactivity. We summarize structurally similar photocatalysts indicating different reaction pathways some catalytic systems, addressing cases radical exceed Additionally, perform a kinetic analysis to explain in on subpicosecond time scales. further rationalize potential anti-Kasha reactivity higher states femtosecond lifetimes, highlighting how future photocatalysis advancements could unlock new photochemical pathways.

Language: Английский

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Electro‐mediated PhotoRedox Catalysis for Selective C(sp³)–O Cleavages of Phosphinated Alcohols to Carbanions

Angewandte Chemie International Edition, Journal Year: 2021, Volume and Issue: 60(38), P. 20817 - 20825

Published: June 24, 2021

We report a novel example of electro-mediated photoredox catalysis (e-PRC) in the reductive cleavage C(sp

Language: Английский

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Electrochemical Activation of Diverse Conventional Photoredox Catalysts Induces Potent Photoreductant Activity**

Angewandte Chemie International Edition, Journal Year: 2021, Volume and Issue: 60(39), P. 21418 - 21425

Published: July 20, 2021

Herein, we disclose that electrochemical stimulation induces new photocatalytic activity from a range of structurally diverse conventional photocatalysts. These studies uncover electron-primed photoredox catalyst capable promoting the reductive cleavage strong C(sp2 )-N and )-O bonds. We illustrate several examples synthetic utility these deeply reducing but otherwise safe mild catalytic conditions. Finally, employ current measurements to perform reaction progress kinetic analysis. This technique reveals improved this system is consequence an enhanced stability profile.

Language: Английский

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