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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Organic Electrochemistry: Molecular Syntheses with Potential

ACS Central Science, Journal Year: 2021, Volume and Issue: 7(3), P. 415 - 431

Published: March 9, 2021

Efficient and selective molecular syntheses are paramount to

Language: Английский

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Electro-organic synthesis – a 21^stcentury technique

Chemical Science, Journal Year: 2020, Volume and Issue: 11(46), P. 12386 - 12400

Published: Jan. 1, 2020

This perspective provides insight into recent electro-organic methods and general trends in this field, opens up prospects for future viewpoints.

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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A Decade of Electrochemical Dehydrogenative C,C-Coupling of Aryls

Accounts of Chemical Research, Journal Year: 2019, Volume and Issue: 53(1), P. 45 - 61

Published: Dec. 18, 2019

The importance of sustainable and green synthetic protocols for the synthesis fine chemicals has rapidly increased during last decades in an effort to reduce use fossil fuels other finite resources. replacement common reagents by electricity provides a cost- atom-efficient, environmentally friendly, inherently safe access novel routes. selective formation carbon-carbon bonds between two distinct substrates is crucial tool organic chemistry. This fundamental transformation enables broad variety complex molecular architectures. In particular, aryl-aryl bond high significance preparation materials, drugs, natural products. Besides well-known well-established reductive- oxidative-reagent-mediated or transition-metal-catalyzed coupling reactions, have arisen, which require fewer steps than conventional approaches. Electroorganic conversions can be categorized according nature electron transfer processes occurring. Direct transformations at inert electrode materials are benign cost-effective, whereas catalytic active electrodes mediated electrosynthesis using additional soluble reagent beneficial properties terms selectivity reactivity. general, these challenging optimization reaction parameters appropriate cell design. Galvanostatic reactions enable fast with rather simple setup, potentiostatic electrolysis may enhance selectivity. Account discusses development seminal formations over past decades, focusing on phenols leading precursors ligands in, e.g., hydroformylation reaction. A key element success electrochemical application electrochemically inert, non-nucleophilic, highly fluorinated alcohols such as 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP), exhibit large potential window cross-coupling reactions. based capability HFIP stabilize radicals. Inert, carbon-based metal-free like graphite boron-doped diamond (BDD) open up electroorganic pathways. Furthermore, been developed intra- intermolecular dehydrogenative electron-rich aryls. 2,2'-biphenol derivatives ligand components catalysts requires carried out larger scale. order achieve this, continuous flow established overcome drawbacks heat transfer, overconversion, conductivity. Modular designs into processes. Recent results demonstrate electrochemistry product pharmaceutically relevant opiate alkaloids (-)-thebaine (-)-oxycodone.

Language: Английский

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Reductive Electrophotocatalysis: Merging Electricity and Light To Achieve Extreme Reduction Potentials

Journal of the American Chemical Society, Journal Year: 2020, Volume and Issue: 142(5), P. 2087 - 2092

Published: Jan. 17, 2020

We describe a new electrophotocatalytic strategy that harnesses the power of light and electricity to generate an excited radical anion with reducing potential -3.2 V vs SCE, which can be used activate substrates very high reduction potentials (Ered ≈ -1.9 -2.9 V). The resultant aryl radicals engaged in various synthetically useful transformations furnish arylboronate, arylstannane, biaryl products.

Language: Английский

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Making electrochemistry easily accessible to the synthetic chemist

Green Chemistry, Journal Year: 2020, Volume and Issue: 22(11), P. 3358 - 3375

Published: Jan. 1, 2020

This tutorial bridges an important knowledge gap by providing easily accessible introduction that enables synthetic chemists to explore electrochemistry.

Language: Английский

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Scalable Photoelectrochemical Dehydrogenative Cross‐Coupling of Heteroarenes with Aliphatic C−H Bonds

Angewandte Chemie International Edition, Journal Year: 2020, Volume and Issue: 59(34), P. 14275 - 14280

Published: June 3, 2020

Heteroarenes are structural motifs found in many bioactive compounds and functional materials. Dehydrogenative cross-coupling of heteroarenes with aliphatic C-H bonds provides straightforward access to functionalized from readily available Established methods employ stoichiometric chemical oxidants under conditions heating or light irradiation. By merging electrochemistry photochemistry, we have achieved efficient photoelectrochemical dehydrogenative C(sp3 )-H donors through H2 evolution, without the addition metal catalysts oxidants. Mechanistically, donor is converted a nucleophilic carbon radical H-atom transfer chlorine atom, which produced by irradiation anodically generated Cl2 Cl- . The then undergoes substitution heteroarene afford alkylated products.

Language: Английский

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Designing Sites in Heterogeneous Catalysis: Are We Reaching Selectivities Competitive With Those of Homogeneous Catalysts?

Chemical Reviews, Journal Year: 2022, Volume and Issue: 122(9), P. 8594 - 8757

Published: March 3, 2022

A critical review of different prominent nanotechnologies adapted to catalysis is provided, with focus on how they contribute the improvement selectivity in heterogeneous catalysis. Ways modify catalytic sites range from use reversible or irreversible adsorption molecular modifiers immobilization tethering homogeneous catalysts and development well-defined solid surfaces. The latter covers methods for dispersion single-atom within supports as well complex nanostructures, it includes post-modification materials via processes such silylation atomic layer deposition. All these methodologies exhibit both advantages limitations, but all offer new avenues design specific applications. Because high cost most fact that resulting may limited thermal chemical stability, be best aimed at improving selective synthesis value-added chemicals, incorporated organic schemes, other applications are being explored address problems energy production, instance, greener processes. details each approaches discussed, representative examples provided. We conclude some general remarks future this field.

Language: Английский

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Photoelectrochemical C−H Alkylation of Heteroarenes with Organotrifluoroborates

Angewandte Chemie International Edition, Journal Year: 2019, Volume and Issue: 58(14), P. 4592 - 4595

Published: Jan. 16, 2019

A photoelectrochemical method for the C-H alkylation of heteroarenes with organotrifluoroborates has been developed. The merger electrocatalysis and photoredox catalysis provides a chemical oxidant-free approach generation functionalization alkyl radicals from organotrifluoroborates. variety were functionalized using primary, secondary, tertiary alkyltrifluoroborates excellent regio- chemoselectivity.

Language: Английский

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