Photocatalytic Late-Stage C–H Functionalization

Chemical Reviews, Journal Year: 2023, Volume and Issue: 123(8), P. 4237 - 4352

Published: Jan. 24, 2023

The emergence of modern photocatalysis, characterized by mildness and selectivity, has significantly spurred innovative late-stage C–H functionalization approaches that make use low energy photons as a controllable source. Compared to traditional strategies, photocatalysis paves the way toward complementary and/or previously unattainable regio- chemoselectivities. Merging compelling benefits with workflow offers potentially unmatched arsenal tackle drug development campaigns beyond. This Review highlights photocatalytic strategies small-molecule drugs, agrochemicals, natural products, classified according targeted bond newly formed one. Emphasis is devoted identifying, describing, comparing main mechanistic scenarios. draws critical comparison between established ionic chemistry photocatalyzed radical-based manifolds. aims establish current state-of-the-art illustrate key unsolved challenges be addressed in future. authors aim introduce general readership functionalization, specialist practitioners evaluation methodologies, potential for improvement, future uncharted directions.

Language: Английский

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Photoelectrochemical asymmetric catalysis enables site- and enantioselective cyanation of benzylic C–H bonds

Nature Catalysis, Journal Year: 2022, Volume and Issue: 5(10), P. 943 - 951

Published: Oct. 10, 2022

Language: Английский

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Red Light-Based Dual Photoredox Strategy Resembling the Z-Scheme of Natural Photosynthesis

JACS Au, Journal Year: 2022, Volume and Issue: 2(6), P. 1488 - 1503

Published: June 10, 2022

Photoredox catalysis typically relies on the use of single chromophores, whereas strategies, in which two different light absorbers are combined, rare. In photosystems I and II green plants, separate chromophores P680 P700 both absorb independently one another, then their excitation energy is combined so-called Z-scheme, to drive an overall reaction that thermodynamically very demanding. Here, we adapt this concept perform photoredox reactions organic substrates with input red photons instead blue or UV light. Specifically, a CuI bis(α-diimine) complex combination situ formed 9,10-dicyanoanthracenyl radical anion presence excess diisopropylethylamine catalyzes ca. 50 dehalogenation detosylation reactions. This dual approach seems useful because less damaging has greater penetration depth than radiation. UV-vis transient absorption spectroscopy reveals subtle change solvent from acetonitrile acetone induces changeover mechanism, involving either dominant photoinduced electron transfer triplet-triplet pathway. Our study illustrates mechanistic complexity systems operating under multiphotonic conditions, it provides insights into how competition between desirable unwanted steps can become more controllable.

Language: Английский

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Mechanisms and Synthetic Strategies in Visible Light‐Driven [2+2]‐Heterocycloadditions

Angewandte Chemie International Edition, Journal Year: 2022, Volume and Issue: 62(8)

Published: Dec. 28, 2022

The synthesis of four membered heterocycles usually requires multi-step procedures and prefunctionalized reactants. A straightforward alternative is the photochemical [2+2]-heterocycloaddition between an alkene a carbonyl derivative, conventionally based on photoexcitation this latter. However, approach limited by absorption profile carbonyl, requiring in most cases use high-energy UV-light, that often results undesired side reactions and/or degradation reaction components. development new milder visible light-driven [2+2]-heterocycloadditions is, therefore, highly desirable. In Review, we highlight relevant achievements promoted light, with particular emphasis involved mechanisms. open challenges will also be discussed, suggesting possible evolutions, stimulating methodological developments field.

Language: Английский

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Sensitizer-controlled photochemical reactivityviaupconversion of red light

Chemical Science, Journal Year: 2022, Volume and Issue: 14(1), P. 149 - 161

Published: Dec. 1, 2022

By combining the energy input from two red photons, chemical reactions that would normally require blue or ultraviolet irradiation become accessible. Key advantages of this biphotonic excitation strategy are light usually penetrates deeper into complex reaction mixtures and causes less photo-damage than direct illumination in ultraviolet. Here, we demonstrate primary light-absorber a dual photocatalytic system comprised transition metal-based photosensitizer an organic co-catalyst can completely alter outcome. Photochemical reductions achieved with copper(i) presence sacrificial electron donor, whereas oxidative substrate activation occurs osmium(ii) photosensitizer. Based on time-resolved laser spectroscopy, changeover photochemical reactivity is due to different underlying mechanisms. Following triplet transfer 9,10-dicyanoanthracene (DCA) subsequent triplet-triplet annihilation upconversion, fluorescent singlet excited state DCA triggers activation, which initiates

Language: Английский

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Shining Fresh Light on Complex Photoredox Mechanisms through Isolation of Intermediate Radical Anions

ACS Catalysis, Journal Year: 2023, Volume and Issue: 13(14), P. 9392 - 9403

Published: June 30, 2023

Photoredox catalysis (PRC) has gained enormous and wide-ranging interest in recent years but also been subject to significant mechanistic uncertainty, even controversy. To provide a method by which the missing understanding can begin be filled in, we demonstrate herein that it is possible isolate as authentic materials one-electron reduction products of representative PRC catalysts (PCs). Specifically, KC8 both 9,10-dicyanoanthracene naphthalene monoamide derivative presence cryptand provides convenient access corresponding [K(crypt)+][PC·-] salts clean fully characterized techniques including EPR XRD. Because PC·- states are key intermediates reactions, such isolation allows for highly controlled study these anions' specific reactivity hence their roles. As demonstration this principle, show used conveniently interrogate mechanisms recent, high-profile "conPET" "e-PRC" currently acute Using very simple experiments, able striking insights into reactions' underlying observe surprising levels hidden complexity would otherwise have challenging identify emphasize care control needed when interrogating interpreting mechanisms. These studies foundation far broader range questions around conPET, e-PRC, other reaction future, using same strategy isolation.

Language: Английский

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Organophotocatalytic Mechanisms: Simplicity or Naïvety? Diverting Reactive Pathways by Modifications of Catalyst Structure, Redox States and Substrate Preassemblies

ChemCatChem, Journal Year: 2023, Volume and Issue: 15(11)

Published: Feb. 21, 2023

Abstract Photocatalysis is a powerful tool to assemble diverse chemical scaffolds, yet bottleneck on its further development the understanding of multitude possible pathways when practitioners rely only oversimplified thermodynamic and optical factors. Recently, there growing number studies in field that exploit, inter alia , kinetic parameters organophotocatalysts are synthetically more programmable terms their redox states opportunities for aggregation with target substrate. Non‐covalent interactions play key role enables access new generation reactivities such as those open‐shell organophotocatalysts. In this review, we discuss how targeted structural modifications influence organophotocatalytic mechanisms together underlying principles. We also highlight benefits strategies preassembly static quenching overcome common reactivity issues (e. g., diffusion rate limits energetic limits).

Language: Английский

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Photoredox catalysis harvesting multiple photon or electrochemical energies

Beilstein Journal of Organic Chemistry, Journal Year: 2023, Volume and Issue: 19, P. 1055 - 1145

Published: July 28, 2023

Photoredox catalysis (PRC) is a cutting-edge frontier for single electron-transfer (SET) reactions, enabling the generation of reactive intermediates both oxidative and reductive processes via photon activation catalyst. Although this represents significant step towards chemoselective and, more generally, sustainable chemistry, its efficacy limited by energy visible light photons. Nowadays, excellent alternative conditions are available to overcome these limitations, harvesting two different but correlated concepts: use multi-photon such as consecutive photoinduced electron transfer (conPET) combination photo- electrochemistry in synthetic photoelectrochemistry (PEC). Herein, we review most recent contributions fields activations organic functional groups. New opportunities chemists captured, selective reactions employing super-oxidants super-reductants engage unactivated chemical feedstocks, scalability up gram scales continuous flow. This provides comparisons between techniques (multi-photon photoredox PEC) help reader fully understand their similarities, differences potential applications therefore choose which method appropriate given reaction, scale purpose project.

Language: Английский

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Electron‐Poor Acridones and Acridiniums as Super Photooxidants in Molecular Photoelectrochemistry by Unusual Mechanisms

Angewandte Chemie International Edition, Journal Year: 2023, Volume and Issue: 62(44)

Published: Aug. 16, 2023

Abstract Electron‐deficient acridones and in situ generated acridinium salts are reported as potent, closed‐shell photooxidants that undergo surprising mechanisms. When bridging acyclic triarylamine catalysts with a carbonyl group (acridones), this completely diverts their behavior away from open‐shell, radical cationic, ‘beyond diffusion’ photocatalysis to closed‐shell, neutral, diffusion‐controlled photocatalysis. Brønsted acid activation of dramatically increases excited state oxidation power (by +0.8 V). Upon reduction protonated acridones, they transform electron‐deficient even more potent (* E 1/2 =+2.56–3.05 V vs SCE). These oxidize arenes where conventional salt have thusfar been limited electron‐rich arenes. Surprisingly, upon photoexcitation these appear two electron reductive quenching form acridinide anions, spectroscopically‐detected forms. This new behaviour is partly enabled by catalyst preassembly the arene, contrasts SET salts. Critically, study illustrates how redox active chromophoric molecules initially considered photocatalysts can during reaction catalytically species different spectroscopic properties.

Language: Английский

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Late-stage modification of bioactive compounds: Improving druggability through efficient molecular editing

Acta Pharmaceutica Sinica B, Journal Year: 2023, Volume and Issue: 14(3), P. 1030 - 1076

Published: Nov. 18, 2023

Synthetic chemistry plays an indispensable role in drug discovery, contributing to hit compounds identification, lead optimization, candidate drugs preparation, and so on. As Nobel Prize laureate James Black emphasized, "the most fruitful basis for the discovery of a new is start with old drug"

Language: Английский

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