The Persistent Radical Effect in Organic Synthesis

Angewandte Chemie International Edition, Journal Year: 2019, Volume and Issue: 59(1), P. 74 - 108

Published: May 22, 2019

Abstract Radical–radical couplings are mostly nearly diffusion‐controlled processes. Therefore, the selective cross‐coupling of two different radicals is challenging and not a synthetically valuable transformation. However, if have lifetimes they generated at equal rates, will become dominant process. This high cross‐selectivity based on kinetic phenomenon called persistent radical effect (PRE). In this Review, an explanation PRE supported by simulations simple model systems provided. Radical stabilities discussed within context their lifetimes, various examples PRE‐mediated radical–radical in synthesis summarized. It shown that restricted to coupling with transient radical. If one partner longer‐lived than other radical, operates achieved. important point expands scope chemistry. The Review divided into parts, namely 1) or organic 2) “radical–metal crossover reactions”; here, metal‐centered species more generally transition‐metal complexes able react discussed—a field has flourished recently.

Language: Английский

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Recent advances of 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN) in photocatalytic transformations

Chemical Communications, Journal Year: 2019, Volume and Issue: 55(38), P. 5408 - 5419

Published: Jan. 1, 2019

In this review, the recent advances of application 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN) as a photoredox catalyst in past three years (2016–2018) for various organic reactions are summarized.

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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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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Organic thermally activated delayed fluorescence (TADF) compounds used in photocatalysis

Chemical Society Reviews, Journal Year: 2021, Volume and Issue: 50(13), P. 7587 - 7680

Published: Jan. 1, 2021

Organic compounds that show Thermally Activated Delayed Fluorescence (TADF) have become wildly popular as next generation emitters in organic light-emitting diodes (OLEDs), but since 2016, received significant and increasing attention photocatalysts.

Language: Английский

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Potent Reductants via Electron-Primed Photoredox Catalysis: Unlocking Aryl Chlorides for Radical Coupling

Journal of the American Chemical Society, Journal Year: 2020, Volume and Issue: 142(5), P. 2093 - 2099

Published: Jan. 17, 2020

We describe a new catalytic strategy to transcend the energetic limitations of visible light by electrochemically priming photocatalyst prior excitation. This system is able productively engage aryl chlorides with reduction potentials hundreds millivolts beyond potential Na0 in productive radical coupling reactions. The radicals produced via this can be leveraged for both carbon–carbon and carbon–heteroatom bond-forming Through direct comparison, we illustrate reactivity selectivity advantages approach relative electrolysis photoredox catalysis.

Language: Английский

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Alkoxy Radicals See the Light: New Paradigms of Photochemical Synthesis

Chemical Reviews, Journal Year: 2021, Volume and Issue: 122(2), P. 2429 - 2486

Published: Oct. 6, 2021

Alkoxy radicals are highly reactive species that have long been recognized as versatile intermediates in organic synthesis. However, their development has impeded due to a lack of convenient methods for generation. Thanks advances photoredox catalysis, enabling facile access alkoxy from bench-stable precursors and free alcohols under mild conditions, research interest this field renewed. This review comprehensively summarizes the recent progress radical-mediated transformations visible light irradiation. Elementary steps radical generation either or central reaction development; thus, each section is categorized discussed accordingly. Throughout review, we focused on different mechanisms well impact synthetic utilizations. Notably, catalytic abundant still early stage, providing intriguing opportunities exploit diverse paradigms.

Language: Английский

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Strategies to Generate Nitrogen-centered Radicals That May Rely on Photoredox Catalysis: Development in Reaction Methodology and Applications in Organic Synthesis

Chemical Reviews, Journal Year: 2021, Volume and Issue: 122(2), P. 2353 - 2428

Published: Oct. 8, 2021

For more than 70 years, nitrogen-centered radicals have been recognized as potent synthetic intermediates. This review is a survey designed for use by chemists engaged in target-oriented synthesis. summarizes the recent paradigm shift access to and application of N-centered enabled visible-light photocatalysis. broadens streamlines approaches many small molecules because photocatalysis conditions are mild. Explicit attention paid innovative advances N–X bonds radical precursors, where X = Cl, N, S, O, H. clarity, key mechanistic data noted, available. Synthetic applications limitations summarized illuminate tremendous utility photocatalytically generated radicals.

Language: Английский

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Photocarboxylation of Benzylic C–H Bonds

Journal of the American Chemical Society, Journal Year: 2019, Volume and Issue: 141(29), P. 11393 - 11397

Published: July 8, 2019

The carboxylation of sp3-hybridized C–H bonds with CO2 is a challenging transformation. Herein, we report visible-light-mediated benzylic into 2-arylpropionic acids under metal-free conditions. Photo-oxidized triisopropylsilanethiol was used as the hydrogen atom transfer catalyst to afford radical that accepts an electron from reduced form 2,3,4,6-tetra(9H-carbazol-9-yl)-5-(1-phenylethyl)benzonitrile generated in situ. resulting carbanion reacts generate corresponding carboxylic acid after protonation. reaction proceeded without addition any sacrificial donor, acceptor or stoichiometric additives. Moderate good yields desired products were obtained broad substrate scope. Several drugs successfully synthesized using novel strategy.

Language: Английский

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Heavy-atom-free BODIPY photosensitizers with intersystem crossing mediated by intramolecular photoinduced electron transfer

Organic & Biomolecular Chemistry, Journal Year: 2019, Volume and Issue: 18(1), P. 10 - 27

Published: Nov. 12, 2019

Organic photosensitizers possessing efficient intersystem crossing (ISC) and forming long-living triplet excited states, play a crucial role in number of applications. A common approach the design such dyes relies on introduction heavy atoms (e.g. transition metals or halogens) into structure, which promote ISC via spin-orbit coupling interaction. In recent years, alternative methods to enhance have been actively studied. Among those, generation states through photoinduced electron transfer (PET) heavy-atom-free molecules has attracted particular attention because it allows for development with programmed state fluorescence quantum yields. Due their synthetic accessibility tunability optical properties, boron dipyrromethenes (BODIPYs) are so far most perspective class operating this mechanism. This article reviews recently reported BODIPY donor-acceptor dyads dimers produce generate singlet oxygen. Structural factors affect PET concomitant formation these discussed data yields oxygen various solvents summarized. Finally, examples applications systems highlighted.

Language: Английский

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