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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Electrocatalysis as an enabling technology for organic synthesis

Chemical Society Reviews, Journal Year: 2021, Volume and Issue: 50(14), P. 7941 - 8002

Published: Jan. 1, 2021

Electrochemistry has recently gained increased attention as a versatile strategy for achieving challenging transformations at the forefront of synthetic organic chemistry. Electrochemistry's unique ability to generate highly reactive radical and ion intermediates in controlled fashion under mild conditions inspired development number new electrochemical methodologies preparation valuable chemical motifs. Particularly, recent developments electrosynthesis have featured an use redox-active electrocatalysts further enhance control over selective formation downstream reactivity these intermediates. Furthermore, electrocatalytic mediators enable proceed manner that is mechanistically distinct from purely methods, allowing subversion kinetic thermodynamic obstacles encountered conventional synthesis. This review highlights key innovations within past decade area electrocatalysis, with emphasis on mechanisms catalyst design principles underpinning advancements. A host oxidative reductive are discussed grouped according classification transformation nature electrocatalyst.

Language: Английский

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Electrocatalytic C–H Activation

ACS Catalysis, Journal Year: 2018, Volume and Issue: 8(8), P. 7086 - 7103

Published: June 18, 2018

C–H activation has emerged as a transformative tool in molecular synthesis, but until recently oxidative activations have largely involved the use of stoichiometric amounts expensive and toxic metal oxidants, compromising overall sustainable nature chemistry. In sharp contrast, electrochemical been identified more efficient strategy that exploits storable electricity place byproduct-generating chemical reagents. Thus, transition-metal catalysts were shown to enable versatile reactions manner. While palladium catalysis set stage for C(sp2)–H C(sp3)–H functionalizations by N-containing directing groups, rhodium ruthenium allowed weakly coordinating amides acids. contrast these precious 4d transition metals, recent year witnessed emergence cobalt oxygenations, nitrogenations, C–C-forming [4+2] alkyne annulations. Thereby, silver(I) oxidants was prevented, improving environmentally benign catalysis. Herein, we summarize major advances organometallic otherwise inert bonds electrocatalysis through May 2018.

Language: Английский

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Recent Advances in C–H Functionalization Using Electrochemical Transition Metal Catalysis

ACS Catalysis, Journal Year: 2018, Volume and Issue: 8(8), P. 7179 - 7189

Published: June 19, 2018

Electrochemical transition metal catalysis is a powerful strategy for organic synthesis because it obviates the use of stoichiometric chemical oxidants and reductants. C–H bond functionalization offers variety useful conversions simple ubiquitous molecules into diverse functional groups in single synthetic operation. This review summarizes recent progress merging electrochemistry with metal-catalyzed functionalization, specifically C–C, C–X (halogen), C–O, C–P, C–N formation.

Language: Английский

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Electrochemical Oxidation of Organic Molecules at Lower Overpotential: Accessing Broader Functional Group Compatibility with Electron−Proton Transfer Mediators

Accounts of Chemical Research, Journal Year: 2020, Volume and Issue: 53(3), P. 561 - 574

Published: Feb. 12, 2020

ConspectusElectrochemical organic oxidation reactions are highly appealing because protons often effective terminal electron acceptors, thereby avoiding undesirable stoichiometric oxidants. These plagued by high overpotentials, however, that greatly limit their utility. Single-electron transfer (SET) from molecules generates high-energy radical-cations. Formation of such intermediates requires electrode potentials far above the thermodynamic reaction and frequently causes decomposition and/or side ancillary functional groups. In this Account, we show how electrocatalytic electron–proton mediators (EPTMs) address challenge. EPTMs bypass formation radical-cation supporting mechanisms operate at much lower (≥1 V) than those analogous direct electrolysis reactions.The stable aminoxyl radical TEMPO (2,2,6,6-tetramethylpiperidine N-oxyl) is an mediator for electrochemical alcohol oxidation, have employed processes applications ranging pharmaceutical synthesis to biomass conversion. A complementary method employs a cooperative Cu/TEMPO system operates 0.5 V potential TEMPO-only mediated process. This difference, which arises different catalytic mechanism, rationalizes broad group tolerance Cu/TEMPO-based aerobic catalysts.Aminoxyl long-standing challenges in "Shono oxidation," important α-C–H tertiary amides carbamates. Shono oxidations initiated high-potential SET step limits Aminoxyl-mediated Shono-type been developed tolerate diverse Analogous reactivity underlies cyanation secondary cyclic amines, new enables efficient diversification piperidine-based building blocks preparation non-natural amino acids.Electrochemical benzylic C–H bonds commonly generate arene cations, but methods again large overpotentials. Mediated promote hydrogen-atom-transfer (HAT) Fe-oxo species phthalimide N-oxyl (PINO) support oxygenation, iodination, oxidative-coupling reactions. merges photochemistry with electrochemistry achieve amidation C(sp3)–H bonds. unique process overpotentials compatible groups.These results implications electrochemistry, highlighting importance "overpotential" considerations prospects expanding synthetic utility using outer-sphere electron-transfer mechanisms. Principles demonstrated here equally relevant reductions.

Language: Английский

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Advances on the Merger of Electrochemistry and Transition Metal Catalysis for Organic Synthesis

Chemical Reviews, Journal Year: 2021, Volume and Issue: 122(3), P. 3180 - 3218

Published: Nov. 19, 2021

Synthetic organic electrosynthesis has grown in the past few decades by achieving many valuable transformations for synthetic chemists. Although electrocatalysis been popular improving selectivity and efficiency a wide variety of energy-related applications, last two decades, there much interest to develop conceptually novel transformations, selective functionalization, sustainable reactions. This review discusses recent advances combination electrochemistry homogeneous transition-metal catalysis synthesis. The enabling mechanistic studies are presented alongside advantages as well future directions address challenges metal-catalyzed electrosynthesis.

Language: Английский

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Copper-Catalyzed Electrochemical C–H Amination of Arenes with Secondary Amines

Journal of the American Chemical Society, Journal Year: 2018, Volume and Issue: 140(36), P. 11487 - 11494

Published: Aug. 30, 2018

Electrochemical oxidation represents an environmentally friendly solution to conventional methods that require caustic stoichiometric chemical oxidants. However, C–H functionalizations merging transition-metal catalysis and electrochemical techniques are, date, largely confined the use of precious metals divided cells. Herein, we report first examples copper-catalyzed aminations arenes at room temperature using undivided cells, thereby providing a practical for construction arylamines. The n-Bu4NI as redox mediator is crucial this transformation. On basis mechanistic studies including kinetic profiles, isotope effects, cyclic voltammetric analyses, radical inhibition experiments, reaction appears proceed via single-electron-transfer (SET) process, high valent Cu(III) species likely involved. These findings provide new avenue transition-metal-catalyzed functionalization reactions mediators.

Language: Английский

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Recent advances in organic electrosynthesis employing transition metal complexes as electrocatalysts

Science Bulletin, Journal Year: 2021, Volume and Issue: 66(23), P. 2412 - 2429

Published: July 13, 2021

Language: Английский

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Late-stage difluoromethylation: concepts, developments and perspective

Chemical Society Reviews, Journal Year: 2021, Volume and Issue: 50(14), P. 8214 - 8247

Published: Jan. 1, 2021

This review describes the conceptual advances that have led to multiple difluoromethylation processes making use of well-defined CF₂H sources.

Language: Английский

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