Transition Metal-Catalyzed C–H Amination: Scope, Mechanism, and Applications

Chemical Reviews, Journal Year: 2017, Volume and Issue: 117(13), P. 9247 - 9301

Published: Jan. 4, 2017

Catalytic transformation of ubiquitous C-H bonds into valuable C-N offers an efficient synthetic approach to construct N-functionalized molecules. Over the last few decades, transition metal catalysis has been repeatedly proven be a powerful tool for direct conversion cheap hydrocarbons synthetically versatile amino-containing compounds. This Review comprehensively highlights recent advances in intra- and intermolecular amination reactions utilizing late metal-based catalysts. Initial discovery, mechanistic study, additional applications were categorized on basis scaffolds types reactions. Reactivity selectivity novel systems are discussed three sections, with each being defined by proposed working mode.

Language: Английский

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Electrochemical strategies for C–H functionalization and C–N bond formation

Chemical Society Reviews, Journal Year: 2018, Volume and Issue: 47(15), P. 5786 - 5865

Published: Jan. 1, 2018

This review provides an overview of the use electrochemistry as appealing platform for expediting carbon–hydrogen functionalization and carbon–nitrogen bond formation.

Language: Английский

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Chemistry with Electrochemically Generated N-Centered Radicals

Accounts of Chemical Research, Journal Year: 2019, Volume and Issue: 52(12), P. 3339 - 3350

Published: Nov. 27, 2019

N-centered radicals are versatile reaction intermediates that can react with various π systems to construct C-N bonds. Current methods for generating usually involve the cleavage of an N-heteroatom bond; however, similar strategies applicable N-H bonds prove be more challenging develop and therefore attracting increasing attention. In this Account, we summarize our recent efforts in development electrochemical generation synthetic utilization radicals. studies, N-aryl amidyl radical, amidinyl radical iminyl cation generated from precursors through direct electrolysis or indirect assisted by a redox catalyst. addition, electrocatalytic method converts oximes iminoxyl has also been developed. The electrophilic participate 5-exo 6-exo cyclization alkenes alkynes afford C-centered radicals, which then undergo transformations such as H atom abstraction, single-electron transfer oxidation carbocation, cyclization, aromatic substitution, leading diverse range N-heterocyclic products. Furthermore, cations, intramolecular substitution N-heteroaromatic compounds. Importantly, channeled toward specific product despite presence other competing pathways. For successful electrosynthesis, it is important take into consideration both electron steps associated electrode nonelectrode related processes. A unique feature electrochemistry simultaneous occurrence anodic cathodic reduction, which, Account demonstrates, allows dehydrogenative proceed H2 evolution without need chemical oxidants. solvent reduction continuously generate low concentration base, facilitates substrate oxidation. Such mechanistic paradigm obviates stoichiometric strong bases avoids base-promoted decomposition sensitive substrates materials adjusted control outcome, demonstrated synthesis N-heteroaromatics corresponding N-oxides biaryl ketoximes.

Language: Английский

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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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Photoredox-Catalyzed C–H Functionalization Reactions

Chemical Reviews, Journal Year: 2021, Volume and Issue: 122(2), P. 1925 - 2016

Published: Sept. 29, 2021

The fields of C–H functionalization and photoredox catalysis have garnered enormous interest utility in the past several decades. Many different scientific disciplines relied on strategies including natural product synthesis, drug discovery, radiolabeling, bioconjugation, materials, fine chemical synthesis. In this Review, we highlight use reactions. We separate review into inorganic/organometallic catalysts organic-based catalytic systems. Further subdivision by reaction class─either sp2 or sp3 functionalization─lends perspective tactical for these methods synthetic applications.

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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Photochemical Generation of Nitrogen-Centered Amidyl, Hydrazonyl, and Imidyl Radicals: Methodology Developments and Catalytic Applications

ACS Catalysis, Journal Year: 2017, Volume and Issue: 7(8), P. 4999 - 5022

Published: June 19, 2017

During the past decade, visible light photocatalysis has become a powerful synthetic platform for promoting challenging bond constructions under mild reaction conditions. These photocatalytic systems rely on harnessing energy purposes through generation of reactive but controllable free radical species. Recent progress in area established it as an enabling catalytic strategy and selective nitrogen-centered radicals. The application activation amides, hydrazones, imides represents valuable approach facilitating formation Within span only couple years, significant been made expediting amidyl, hydrazonyl, imidyl radicals from variety precursors. This Perspective highlights recent advances light-mediated these A particular emphasis is placed unique ability accessing elusive manifolds construction diversely functionalized nitrogen-containing motifs nontraditional disconnections contemporary chemistry.

Language: Английский

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Intermolecular radical carboamination of alkenes

Chemical Society Reviews, Journal Year: 2020, Volume and Issue: 49(6), P. 1790 - 1811

Published: Jan. 1, 2020

Vicinal alkene carboamination is a highly efficient and practical synthetic strategy for the straightforward preparation of diverse valuable amine derivatives starting from simple compounds. During last decade that approach has found continuous research interests various methods have been developed using transition-metal catalysis. Driven by renaissance radical chemistry, intermolecular comprising C-C bond C-N forming step intensively investigated recently culminating in novel strategies improved protocols which complement existing methodologies. Radical can be achieved via three different reaction modes. Such cascades proceed through N-radical addition to an with subsequent formation leading 2,1-carboamination products. Alternatively, installed prior initial C-radical β-amination resulting 1,2-carboamination. The third mode comprises single electron oxidation corresponding cation gets trapped N-nucleophile cascade terminated formation. In this review, conceptual approaches will discussed examples recent literature presented. Further, reader get insights into mechanism transformations.

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 radical-based C–N bond formation via photo-/electrochemistry

Chemical Society Reviews, Journal Year: 2018, Volume and Issue: 47(8), P. 2591 - 2608

Published: Jan. 1, 2018

The employment of nitrogen sources with free N-H bonds for amination is considered to be most straightforward and desirable, especially when the C-N are prepared from non-functionalized carbon sources, such as C-H C-C double/triple bonds, since this obviates needs pre-installation reactive groups in starting materials leads a high atom step economy. Recently, radical chemistry has been resuscitated owing its great value organic synthesis, notable advances have made direct use radical-based bond formation photo-/electrotechniques. Apart well-studied N-radical species addition pathway, radical-mediated aminations also proceed through N-atom nucleophilic addition, C-/N-radical cross-coupling, hydrogen-atom transfer (HAT) process. This review highlights recent area emphasis on related reaction mechanisms.

Language: Английский

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