Visible Light-Driven Radical-Mediated C–C Bond Cleavage/Functionalization in Organic Synthesis

Chemical Reviews, Journal Year: 2020, Volume and Issue: 121(1), P. 506 - 561

Published: May 29, 2020

Thermal C–C bond cleavage reactions allow the construction of structurally diverse molecular skeletons via predictable and efficient reorganizations. Visible light photoredox-catalyzed radical-mediated have recently emerged as a powerful alternative method for overcoming thermodynamic kinetic barrier in scaffolds. In recent years, plethora elegant useful been invented, products are sometimes otherwise inaccessible by classic thermal reactions. Considering great influence synthetic potential these reactions, we provide summary state art visible light-driven cleavage/functionalization strategies with specific emphasis on working models. We hoped that this review will be medicinal organic chemists inspire further reaction development interesting area.

Language: Английский

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Visible Light-Induced Transition Metal Catalysis

Chemical Reviews, Journal Year: 2021, Volume and Issue: 122(2), P. 1543 - 1625

Published: Oct. 8, 2021

In recent years, visible light-induced transition metal catalysis has emerged as a new paradigm in organic photocatalysis, which led to the discovery of unprecedented transformations well improvement known reactions. this subfield complex serves double duty by harvesting photon energy and then enabling bond forming/breaking events mostly via single catalytic cycle, thus contrasting established dual photocatalysis an exogenous photosensitizer is employed. addition, approach often synergistically combines catalyst–substrate interaction with photoinduced process, feature that uncommon conventional photoredox chemistry. This Review describes early development advances emerging field.

Language: Английский

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When Light Meets Nitrogen-Centered Radicals: From Reagents to Catalysts

Accounts of Chemical Research, Journal Year: 2020, Volume and Issue: 53(5), P. 1066 - 1083

Published: April 14, 2020

ConspectusNitrogen-centered radicals (NCRs) are a versatile class of highly reactive species that have longer history than the classical carbon-based in synthetic chemistry. Depending on N-hybridization and substitution patterns, NCRs can serve as electrophiles or nucleophiles to undergo various radical transformations. Despite their power, progress nitrogen-radical chemistry is still slow compared with popularity carbon radicals, considerable potential has been largely underexplored, which is, concluded by Zard, mainly hampered "a dearth convenient access these lack awareness pertaining reactivity".Over past decade, visible-light photoredox catalysis established powerful toolbox chemists use generate diverse range intermediates from native organic functional groups via single electron transfer process energy under mild reaction conditions. This catalytic strategy typically obviates need for external stoichiometric activation reagents toxic initiators often enables traditionally inaccessible ionic chemical reactions. On basis our long-standing interest nitrogen catalysis, we emphasized tactic discover develop novel methods generating controlled fashion applications. In this Account, describe recent advances development visible-light-driven photoredox-catalyzed generation applications.Inspired natural biological proton-coupled (PCET) process, first developed oxidative deprotonation activate N–H bonds hydrazones, benzamides, sulfonamides give corresponding With species, then achieved 5-exo 6-endo cyclizations well cascade reactions regioselective manner, providing variety potentially useful heterocycles. To further expand repertoire possible NCRs, also revealed iminyl derived O-acyl cycloalkanone oxime esters, facile ring-opening C–C bond cleavage cyanoalkyl radicals. These newly formed bond-forming allow synthesis distally functionalized alkyl nitriles. Stimulated studies, wide copper-catalyzed cross-coupling Because inherent transient properties, heteroatom-centered underexplored synthesis. Building understanding fundamental time concept NCR covalent involves situ-photogenerated allyl sulfones, vinylcyclopropanes, N-tosyl vinylaziridines. thus enabled efficient difunctionalization alkenes late-stage modification complex biologically active molecules.In panoramic picture contributions since 2014 application systems field studies provide not only functionally rich molecules but some insight into exploration new reactivity modes NCRs.

Language: Английский

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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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Enantioselective Photochemical Reactions Enabled by Triplet Energy Transfer

Chemical Reviews, Journal Year: 2021, Volume and Issue: 122(2), P. 1626 - 1653

Published: July 6, 2021

For molecules with a singlet ground state, the population of triplet states is mainly possible (a) by direct excitation and subsequent intersystem crossing or (b) energy transfer from an appropriate sensitizer. The latter scenario enables catalytic photochemical reaction in which sensitizer adopts role catalyst undergoing several cycles photon absorption to substrate. If product molecule triplet-sensitized process chiral, this can proceed enantioselectively upon judicious choice chiral An enantioselective also occur dual approach which, apart achiral sensitizer, second activates substrate toward sensitization. Although idea reactions via intermediates has been pursued for more than 50 years, notable selectivities exceeding 90% enantiomeric excess (ee) have only realized past decade. This review attempts provide comprehensive survey on various were rendered

Language: Английский

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Transition Metal-Catalyzed Organic Reactions under Visible Light: Recent Developments and Future Perspectives

ACS Catalysis, Journal Year: 2020, Volume and Issue: 10(16), P. 9170 - 9196

Published: July 20, 2020

The development of transition metal (TM) catalysis for organic synthesis under visible light without recourse to typical photoredox catalysts has become a rapidly growing area research and been actively explored in the past several years. Distinct from extensively developed catalysis, which photocatalyst generally does not directly participate bond-forming process, photocatalyst/TM synergistic absorbs photon energy transfers TM catalyst through redox or transfer this Review focuses on summarizing recent developments photocatalytic reactions that use complexes both absorb catalytic bond formation involving covalently bonded intermediate. contents are categorized by used (Pd, Cu, Co, Ni, Mn, Au, Rh, Fe, Ru), with descending sequence according number examples reported each metal, provide an overview April 2020. Future perspectives personal opinions regarding expanding field also discussed.

Language: Английский

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Strategic Use of Visible-Light Photoredox Catalysis in Natural Product Synthesis

Chemical Reviews, Journal Year: 2021, Volume and Issue: 122(2), P. 1717 - 1751

Published: July 7, 2021

Recent progress in the development of photocatalytic reactions promoted by visible light is leading to a renaissance use photochemistry construction structurally elaborate organic molecules. Because rich functionality found natural products, studies product total synthesis provide useful insights into functional group compatibility these new methods as well their impact on synthetic strategy. In this review, we examine syntheses published through end 2020 that employ visible-light photoredox catalytic step. To assist someone interested employing steps discussed, review organized largely nature bond formed

Language: Английский

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Synergistic Dual Transition Metal Catalysis

Chemical Reviews, Journal Year: 2020, Volume and Issue: 120(24), P. 13382 - 13433

Published: Nov. 29, 2020

Synergistic catalysis, a type of plural catalysis which utilizes at least two different catalysts to enable reaction between separately activated substrates, has unlocked plethora previously unattainable transformations and novel chemical reactivity. Despite the appreciable utility synergistic specific examples involving transition metals have been limited, as ensuring judicious choice parameters prevent deactivation catalysts, undesirable monocatalytic event(s) leading side products, or premature termination other potentially troublesome outcomes present formidable challenge. Excluding those driven by photocatalytic mechanisms, this review will highlight reported reactions that make use simultaneous catalytic cycles metal catalysts.

Language: Английский

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Visible‐Light‐Induced Homolysis of Earth‐Abundant Metal‐Substrate Complexes: A Complementary Activation Strategy in Photoredox Catalysis

Angewandte Chemie International Edition, Journal Year: 2021, Volume and Issue: 60(39), P. 21100 - 21115

Published: Feb. 18, 2021

Abstract The mainstream applications of visible‐light photoredox catalysis predominately involve outer‐sphere single‐electron transfer (SET) or energy (EnT) processes precious metal Ru II Ir III complexes organic dyes with low photostability. Earth‐abundant metal‐based M n L ‐type (M=metal, =polydentate ligands) are rapidly evolving as alternative photocatalysts they offer not only economic and ecological advantages but also access to the complementary inner‐sphere mechanistic modes, thereby transcending their inherent limitations ultrashort excited‐state lifetimes for use effective photocatalysts. generic process, termed visible‐light‐induced homolysis (VLIH), entails formation suitable light‐absorbing ligated metal–substrate (M ‐Z; Z=substrate) that can undergo homolytic cleavage generate n−1 Z . further transformations.

Language: Английский

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