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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Catalyzing Electrosynthesis: A Homogeneous Electrocatalytic Approach to Reaction Discovery

Accounts of Chemical Research, Journal Year: 2020, Volume and Issue: 53(3), P. 547 - 560

Published: Feb. 20, 2020

Electrochemistry has been used as a tool to drive chemical reactions for over two centuries. With the help of an electrode and power source, chemists are bestowed with imaginary reagent whose potential can be precisely dialed in. The theoretically infinite redox range renders electrochemistry capable oxidizing or reducing some most tenacious compounds (e.g., F

Language: Английский

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A Survival Guide for the “Electro-curious”

Accounts of Chemical Research, Journal Year: 2019, Volume and Issue: 53(1), P. 72 - 83

Published: Dec. 11, 2019

ConspectusThe appeal and promise of synthetic organic electrochemistry have been appreciated over the past century. In terms redox chemistry, which is frequently encountered when forging new bonds, it difficult to conceive a more economical way add or remove electrons than electrochemistry. Indeed, many largest industrial chemical processes are achieved in practical using as reagent. Why then, after so years documented benefits electrochemistry, not widely embraced by mainstream practitioners? Erroneous perceptions that "black box" combined with lack intuitive inexpensive standardized equipment likely contributed this stagnation interest within community. This barrier entry magnified fact can already be accomplished simple reagents even if they less atom-economic. Time has proven sustainability economics strong enough driving forces for adoption electrochemical techniques broader like chemists dabbled age-old technique, our first foray into area was choice but rather through sheer necessity.The unique reactivity old redox-modulating technique must therefore highlighted leveraged order draw field. Enabling bonds forged higher levels chemo- regioselectivity will accomplish goal. doing so, envisioned widespread go beyond supplanting unsustainable mundane reactions development exciting paradigms enable heretofore unimagined retrosynthetic pathways. Whereas rigorous physical principles electroorganic synthesis reviewed elsewhere, often case such summaries leave out pragmatic aspects designing, optimizing, scaling up preparative reactions. Taken together, task setting an reaction, much inventing one, vexing seasoned chemists. Account features format focuses on addressing exact issue context own studies. The graphically rich presentation style pinpoints basic concepts, typical challenges, key insights those "electro-curious" who seek rapidly explore power their research.

Language: Английский

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Metalla-electrocatalyzed C–H Activation by Earth-Abundant 3d Metals and Beyond

Accounts of Chemical Research, Journal Year: 2019, Volume and Issue: 53(1), P. 84 - 104

Published: Dec. 19, 2019

To improve the efficacy of molecular syntheses, researchers wish to capitalize upon selective modification otherwise inert C-H bonds. The past two decades have witnessed considerable advances in coordination chemistry that set stage for transformative tools functionalizations. Particularly, oxidative C-H/C-H and C-H/Het-H transformations gained major attention because they avoid all elements substrate prefunctionalization. Despite advances, activations been dominated by precious transition metal catalysts based on palladium, ruthenium, iridium, rhodium, thus compromising sustainable nature overall activation approach. same holds true predominant use stoichiometric chemical oxidants regeneration active catalyst, prominently featuring hypervalent iodine(III), copper(II), silver(I) oxidants. Thereby, quantities undesired byproducts are generated, which preventive applications scale. In contrast, elegant merger homogeneous metal-catalyzed with electrosynthesis bears unique power achieve outstanding levels oxidant resource economy. Thus, contrast classical electrosyntheses control, metalla-electrocatalysis huge largely untapped potential unmet site selectivities means catalyst control. While indirect electrolysis using palladium complexes has realized, less toxic expensive base feature distinct beneficial assets toward this Account, I summarize emergence electrocatalyzed earth-abundant 3d metals beyond, a topical focus contributions from our laboratories through November 2019. cobalt electrocatalysis was identified as particularly powerful platform wealth transformations, including oxygenations nitrogenations well alkynes, alkenes, allenes, isocyanides, carbon monoxide, among others. As complementary tools, nickel, copper, very recently iron devised metalla-electrocatalyzed activations. Key success were detailed mechanistic insights, oxidation-induced reductive elimination scenarios. Likewise, development methods make weak O-coordination benefited crucial insights into catalyst's modes action experiment, operando spectroscopy, computation. Overall, thereby syntheses These electrooxidative frequently characterized improved chemoselectivities. Hence, ability dial redox at minimum level required desired transformation renders an ideal functionalization structurally complex molecules sensitive functional groups. This strategy was, inter alia, successfully applied scale-up continuous flow step-economical assembly polycyclic aromatic hydrocarbons.

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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Powering the Future: How Can Electrochemistry Make a Difference in Organic Synthesis?

Chem, Journal Year: 2020, Volume and Issue: 6(10), P. 2484 - 2496

Published: Sept. 24, 2020

Language: Английский

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New Redox Strategies in Organic Synthesis by Means of Electrochemistry and Photochemistry

ACS Central Science, Journal Year: 2020, Volume and Issue: 6(8), P. 1317 - 1340

Published: July 16, 2020

As the breadth of radical chemistry grows, new means to promote and regulate single-electron redox activities play increasingly important roles in driving modern synthetic innovation. In this regard, photochemistry electrochemistry-both considered as niche fields for decades-have seen an explosive renewal interest recent years gradually have become a cornerstone organic chemistry. Outlook article, we examine current state-of-the-art areas electrochemistry photochemistry, well nascent area electrophotochemistry. These techniques employ external stimuli activate molecules imbue privileged control reaction progress selectivity that is challenging traditional chemical methods. Thus, they provide alternative entries known reactive intermediates enable distinct strategies were previously unimaginable. Of many hallmarks, electro- are often classified "green" technologies, promoting reactions under mild conditions without necessity potent wasteful oxidants reductants. This reviews most growth these with special emphasis on conceptual advances given rise enhanced accessibility tools trade.

Language: Английский

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Electrochemical Oxidation Induced Selective C–C Bond Cleavage

Chemical Reviews, Journal Year: 2020, Volume and Issue: 121(1), P. 485 - 505

Published: Oct. 5, 2020

Selective C–C bond cleavage under mild conditions can serve as a valuable tool for organic syntheses and macromolecular degradation. However, the conventional chemical methods have largely involved use of noble transition-metal catalysts well stoichiometric perhaps environmentally unfriendly oxidants, compromising overall sustainable nature transformation chemistry. In this regard, electrochemical has been identified scalable strategy that employs electricity to replace byproduct-generating reagents. To date, progress made in area mainly relied on Kolbe electrolysis related processes. Encouragingly, more examples bonds via other maneuvers recently developed. This review provides an overview most recent significant developments electrochemically oxidative selective cleavage, with emphasis both synthetic outcomes reaction mechanisms, it showcases innate advantages exciting potentials synthesis.

Language: Английский

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