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

---

Direct Photocatalyzed Hydrogen Atom Transfer (HAT) for Aliphatic C–H Bonds Elaboration

Chemical Reviews, Journal Year: 2021, Volume and Issue: 122(2), P. 1875 - 1924

Published: Aug. 6, 2021

Direct photocatalyzed hydrogen atom transfer (d-HAT) can be considered a method of choice for the elaboration aliphatic C–H bonds. In this manifold, photocatalyst (PCHAT) exploits energy photon to trigger homolytic cleavage such bonds in organic compounds. Selective bond may achieved by judicious abstractor (key parameters are electronic character and molecular structure), as well reaction additives. Different classes PCsHAT available, including aromatic ketones, xanthene dyes (Eosin Y), polyoxometalates, uranyl salts, metal-oxo porphyrin tris(amino)cyclopropenium radical dication. The processes (mainly C–C formation) most cases carried out under mild conditions with help visible light. aim review is offer comprehensive survey synthetic applications d-HAT.

Language: Английский

---

Site-Selective C–H Functionalization via Synergistic Use of Electrochemistry and Transition Metal Catalysis

Accounts of Chemical Research, Journal Year: 2020, Volume and Issue: 53(2), P. 300 - 310

Published: Jan. 15, 2020

Electrochemical synthesis of organic compounds has emerged as an attractive and environmentally benign alternative to conventional approaches for oxidation reduction that utilizes electric current instead chemical oxidants reductants. As such, many useful transformations have been developed, including the Kolbe reaction, Simons fluorination process, Monsanto adiponitrile Shono oxidation, name a few. C-H functionalization represents one most promising reaction types among electrochemical transformations, since this process avoids prefunctionalization substrates provides novel retrosynthetic disconnections. However, site-selective anodic bonds is still fundamental challenge due high potentials compared solvents common functional groups. To overcome issue, indirect electrolysis via action mediator (a redox catalyst) regularly employed, by which selectivity can be controlled following said with substrate. Since transition metal complexes easily tuned modification ligand, synergistic use electrochemistry catalysis achieve strategy. In Account, we summarize contextualize our recent efforts toward metal-catalyzed proximal suitable directing group. We developed oxygenation, acylation, alkylation, halogenation reactions in Pd(II) species oxidized Pd(III) or Pd(IV) intermediate followed reductive elimination form corresponding C-O, C-C, C-X bonds. Importantly, improved monofunctionalization achieved Pd-catalyzed C(sp3)-H oxygenation using PhI(OAc)2 oxidant. Physical separators are sometimes used prevent deposition Pd black on cathode resulting from valent species. skirted issue through development Cu-catalyzed C(sp2)-H amination n-Bu4NI cocatalyst undivided cell. addition, Ir-catalyzed vinylic acrylic acids alkynes cell, affording various substituted α-pyrones good excellent yield. More importantly, oxidants, Ag2CO3, Cu(OAc)2, PhI(OAc)2, resulted much lower yields absence electrical under otherwise identical conditions. elaborated below, progress area effective platform friendly sustainable selective transformations.

Language: Английский

---

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

---

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

---

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

---

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

---

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

---

C–H activation

Nature Reviews Methods Primers, Journal Year: 2021, Volume and Issue: 1(1)

Published: June 17, 2021

Language: Английский

---

Electrode Materials in Modern Organic Electrochemistry

Angewandte Chemie International Edition, Journal Year: 2020, Volume and Issue: 59(43), P. 18866 - 18884

Published: July 7, 2020

The choice of electrode material is critical for achieving optimal yields and selectivity in synthetic organic electrochemistry. imparts significant influence on the kinetics thermodynamics electron transfer, frequently defines success or failure a transformation. Electrode processes are complex so often empirical underlying mechanisms rationale unknown. In this review, we aim to highlight recent instances where offered, which should aid future reaction development.

Language: Английский

---