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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Illuminating Photoredox Catalysis

Trends in Chemistry, Journal Year: 2019, Volume and Issue: 1(1), P. 111 - 125

Published: Feb. 23, 2019

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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Visible light photoredox-catalysed remote C–H functionalisation enabled by 1,5-hydrogen atom transfer (1,5-HAT)

Chemical Society Reviews, Journal Year: 2021, Volume and Issue: 50(13), P. 7359 - 7377

Published: Jan. 1, 2021

The generation of heteroatom-centred radicals followed by intramolecular 1,5-HAT and functionalisation the translocated carbon-centred radical is an efficient way to functionalize chemo- regio-selectively remote unactivated C(sp³)–H bond.

Language: Английский

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Pyridinium Salts as Redox‐Active Functional Group Transfer Reagents

Angewandte Chemie International Edition, Journal Year: 2019, Volume and Issue: 59(24), P. 9264 - 9280

Published: Oct. 10, 2019

Abstract In this Review, we highlight recent advances in the understanding and design of N‐functionalized pyridinium scaffolds as redox‐active, single‐electron, functional group transfer reagents. We provide a selection representative methods that demonstrate reactivity fundamental emerging field. The these reagents can be divided into two divergent pathways: homolytic fragmentation to liberate N‐bound substituent corresponding radical or an alternative heterolytic liberates N‐centered radical. A short description elementary steps involved induced by single‐electron is also critically discussed guide readers towards processes thought occur under conditions.

Language: Английский

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Nitrogen-Centered Radicals in Functionalization of sp² Systems: Generation, Reactivity, and Applications in Synthesis

Chemical Reviews, Journal Year: 2022, Volume and Issue: 122(9), P. 8181 - 8260

Published: March 14, 2022

The chemistry of nitrogen-centered radicals (NCRs) has plentiful applications in organic synthesis, and they continue to expand as our understanding these reactive species increases. utility intermediates is demonstrated the recent advances C–H amination (di)amination alkenes. Synthesis previously challenging structures can be achieved by efficient functionalization sp2 moieties without prefunctionalization, allowing for faster more streamlined synthesis. This Review addresses generation, reactivity, application NCRs, including, but not limited to, iminyl, aminyl, amidyl, aminium species. Contributions from early discovery up most examples have been highlighted, covering radical initiation, thermolysis, photolysis, and, recently, photoredox catalysis. Radical-mediated intermolecular (hetero)arenes occur with a variety complex amine precursors, generating aniline derivatives, an important class drug development. Functionalization olefins achievable high anti-Markovnikov regioselectivity allows access difunctionalized when intermediate carbon are trapped. Additionally, reactivity NCRs harnessed rapid construction N-heterocycles such pyrrolidines, phenanthridines, quinoxalines, quinazolinones.

Language: Английский

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Asymmetric Photocatalysis with Bis-cyclometalated Rhodium Complexes

Accounts of Chemical Research, Journal Year: 2019, Volume and Issue: 52(3), P. 833 - 847

Published: March 6, 2019

ConspectusAspects of sustainability are playing an increasingly important role for the development new synthetic methods. In this context, combination asymmetric catalysis, which is considered one most economic strategies to generate nonracemic chiral compounds, and visible light as abundant source energy induce or activate chemical reactions has recently gained much attention. Furthermore, photochemistry with catalysis provides opportunity mechanistically unique reaction schemes. However, such photocatalysis very challenging two main problems can be pinpointed undesirable photochemical background difficulties in controlling stereochemistry photochemically generated highly reactive intermediates.In Account, we present discuss using currently versatile photoactivatable catalysts, namely, bis-cyclometalated rhodium(III) complexes. The catalysts contain inert cyclometalating 5-(tert-butyl)-2-phenyl benzoxazole benzothiazole ligands together labile acetonitriles, overall chirality due a stereogenic metal center. rhodium complexes serve excellent Lewis acids substrates 2-acyl imidazoles N-acyl pyrazoles, which, upon replacement acetonitrile ligands, coordinate center 2-point fashion. These rhodium–substrate intermediates display photophysical properties often photoactive developed This excitation long-lived photoexcited states intrinsic acid reactivity opens door multitude visible-light-induced conversions.In first mode reactivity, function control radical enolates electron-deficient radicals, rhodium-coordinated enones electron-rich rhodium-bound radicals by photoinduced single electron transfer. their ground key while separate photoredox cycles initiate generations via transfer either additional compounds serving catalyst (secondary photocatalysis). second within cycle (primary photocatalysis) undergo stereocontrolled chemistry direct bond forming out excited state. multiple modes intertwining have been applied α- β-alkylations, β-aminations, β-C–H functionalization carbonyl [3 + 2] photocycloadditions between cyclopropanes alkenes alkynes, [2 alkenes, dearomative photocycloadditions, 3] vinyl azides.We anticipate that these schemes (photoactive) will spur photocatalysts catalysis.

Language: Английский

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Copper‐Catalyzed Radical Cross‐Coupling of Redox‐Active Oxime Esters, Styrenes, and Boronic Acids

Angewandte Chemie International Edition, Journal Year: 2018, Volume and Issue: 57(47), P. 15505 - 15509

Published: Oct. 8, 2018

A visible-light-driven, copper-catalyzed three-component radical cross-coupling of oxime esters, styrenes, and boronic acids has been developed. Key steps this protocol involve catalytic generation an iminyl from a redox-active ester subsequent C-C bond cleavage to generate cyanoalkyl radical. Upon its addition styrene, the newly formed benzylic undergoes coupling with boronic-acid-derived ArCuII complex achieve 1,1-diarylmethane-containing alkylnitriles.

Language: Английский

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Photocatalytic hydrogen atom transfer: the philosopher's stone for late-stage functionalization?

Green Chemistry, Journal Year: 2020, Volume and Issue: 22(11), P. 3376 - 3396

Published: Jan. 1, 2020

Applications of photocatalytic Hydrogen Atom Transfer (HAT) methodologies for the Late-Stage Functionalization (LSF) complex molecules have been discussed in this perspective.

Language: Английский

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