Electrifying Organic Synthesis

Angewandte Chemie International Edition, Journal Year: 2018, Volume and Issue: 57(20), P. 5594 - 5619

Published: Jan. 2, 2018

The direct synthetic organic use of electricity is currently experiencing a renaissance. More synthetically oriented laboratories working in this area are exploiting both novel and more traditional concepts, paving the way to broader applications niche technology. As only electrons serve as reagents, generation reagent waste efficiently avoided. Moreover, stoichiometric reagents can be regenerated allow transformation conducted an electrocatalytic fashion. However, application electroorganic transformations than minimizing footprint, it rather gives rise inherently safe processes, reduces number steps many syntheses, allows for milder reaction conditions, provides alternative means access desired structural entities, creates intellectual property (IP) space. When originates from renewable resources, surplus might directly employed terminal oxidizing or reducing agent, providing ultra-sustainable therefore highly attractive technique. This Review surveys recent developments electrochemical synthesis that will influence future area.

Language: Английский

---

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

---

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

---

Mechanistic Studies in Photocatalysis

Angewandte Chemie International Edition, Journal Year: 2018, Volume and Issue: 58(12), P. 3730 - 3747

Published: Oct. 19, 2018

Abstract The fast‐moving fields of photoredox and photocatalysis have recently provided fresh opportunities to expand the potential synthetic organic chemistry. Advances in light‐mediated processes mainly been guided so far by empirical findings quest for reaction invention. general perception, however, is that entering a more mature phase where combination experimental mechanistic studies will play dominant role sustaining further innovation. This Review outlines key consider when developing photochemical process, best techniques available acquiring relevant information. discussion use selected case highlight how investigations can be instrumental guiding invention development synthetically useful photocatalytic transformations.

Language: Английский

---

Electrochemical Arylation Reaction

Chemical Reviews, Journal Year: 2018, Volume and Issue: 118(14), P. 6706 - 6765

Published: July 2, 2018

Arylated products are found in various fields of chemistry and represent essential entities for many applications. Therefore, the formation this structural feature represents a central issue contemporary organic synthesis. By action electricity necessity leaving groups, metal catalysts, stoichiometric oxidizers, or reducing agents can be omitted part even completely. The replacement conventional reagents by sustainable not only will environmentally benign but also allows significant short cuts electrochemical In addition, methodology considered as inherently safe. current survey is organized cathodic anodic conversions well number groups being involved. some electroconversions used regenerated at electrode, whereas other electrotransformations free radical sequences exploited to afford highly process. aryl-substrate bond discussed aromatic substrates, heterocycles, multiple systems, saturated carbon substrates. This covers most seminal work advances past two decades area.

Language: Английский

---

Electrochemical Oxidative Cross-Coupling with Hydrogen Evolution Reactions

Accounts of Chemical Research, Journal Year: 2019, Volume and Issue: 52(12), P. 3309 - 3324

Published: Nov. 27, 2019

Oxidative cross-coupling has proved to be one of the most straightforward strategies for forming carbon-carbon and carbon-heteroatom bonds from easily available precursors. Over past two decades, tremendous efforts have been devoted in this field significant advances achieved. However, order remove surplus electrons substrates chemical formation, stoichiometric oxidants are usually needed. Along with development modern sustainable chemistry, considerable perform oxidative reactions under external-oxidant-free conditions. Electrochemical synthesis is a powerful environmentally benign approach, which can not only achieve cross-couplings conditions, but also release valuable hydrogen gas during bond formation. Recently, electrochemical evolution significantly explored. This Account presents our recent toward reactions. (1) We explored thiols/thiophenols arenes, heteroarenes, alkenes C-S (2) Using strategy C-H/N-H evolution, we successfully realized C-H amination phenols, anilines, imidazopyridines, even ethers. (3) Employing halide salts as green halogenating reagents, developed clean halogenation protocol oxidation To address limitation that reaction had carry out aqueous solvent, an alternative method uses CBr4, CHBr3, CH2Br2, CCl3Br, CCl4 reagents mixture acetonitrile methanol cosolvent. (4) approach constructing C-O well-developed manner. (5) Under mild C(sp2)-H C(sp3)-H phosphonylation modest high yields. (6) achieved S-H/S-H By anodic instead oxidants, overoxidation thiols thiophenols was well avoided. (7) The methods structurally diverse heterocyclic compounds were via annulations. (8) applied difunctionalization multiple step, such C-S/C-O bonds, C-S/C-N C-Se/C-O C-Se/C-N bonds. hope studies will stimulate research interest chemists pave way discovery more

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

---

Recent Advances in Minisci‐Type Reactions

Angewandte Chemie International Edition, Journal Year: 2019, Volume and Issue: 58(39), P. 13666 - 13699

Published: March 20, 2019

Abstract Reactions that involve the addition of carbon‐centered radicals to basic heteroarenes, followed by formal hydrogen atom loss, have become widely known as Minisci‐type reactions. First developed into a useful synthetic tool in late 1960s Minisci, this reaction type has been constant use over last half century chemists seeking functionalize heterocycles rapid and direct manner, avoiding need for de novo heterocycle synthesis. Whilst originally protocols radical generation remain active today, they joined recent years new array strategies allow wider variety precursors often operate under milder more benign conditions. The surge interest transformations based on free reactivity meant numerous choices are now available chemist looking utilize reaction. Radical‐generation methods photoredox catalysis electrochemistry approaches which thermal cleavage or situ reactive precursors. This review will cover remarkably large body literature appeared topic decade an attempt provide guidance chemist, well perspective both challenges overcome those still remain. As logical classification advances nature precursor, with most concerned, control various selectivity aspects associated reactions also be discussed.

Language: Английский

---

Using Physical Organic Chemistry To Shape the Course of Electrochemical Reactions

Chemical Reviews, Journal Year: 2018, Volume and Issue: 118(9), P. 4817 - 4833

Published: March 2, 2018

While organic electrochemistry can look quite different to a chemist not familiar with the technique, reactions are at their core reactions. As such, they developed and optimized using same physical chemistry principles employed during development of any other reaction. Certainly, electron transfer that triggers require consideration new "wrinkles" those principles, but considerations typically minimal relative more traditional approaches needed manipulate pathways available reactive intermediates formed downstream transfer. In this review, three very synthetic challenges-the generation trapping radical cations, site-selective on microelectrode arrays, optimization current in paired electrolysis-are used illustrate point.

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

---