Photochemical Generation of Nitrogen-Centered Amidyl, Hydrazonyl, and Imidyl Radicals: Methodology Developments and Catalytic Applications

ACS Catalysis, Год журнала: 2017, Номер 7(8), С. 4999 - 5022

Опубликована: Июнь 19, 2017

During the past decade, visible light photocatalysis has become a powerful synthetic platform for promoting challenging bond constructions under mild reaction conditions. These photocatalytic systems rely on harnessing energy purposes through generation of reactive but controllable free radical species. Recent progress in area established it as an enabling catalytic strategy and selective nitrogen-centered radicals. The application activation amides, hydrazones, imides represents valuable approach facilitating formation Within span only couple years, significant been made expediting amidyl, hydrazonyl, imidyl radicals from variety precursors. This Perspective highlights recent advances light-mediated these A particular emphasis is placed unique ability accessing elusive manifolds construction diversely functionalized nitrogen-containing motifs nontraditional disconnections contemporary chemistry.

Язык: Английский

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Photons or Electrons? A Critical Comparison of Electrochemistry and Photoredox Catalysis for Organic Synthesis

Chemical Reviews, Год журнала: 2021, Номер 122(2), С. 2487 - 2649

Опубликована: Ноя. 9, 2021

Redox processes are at the heart of synthetic methods that rely on either electrochemistry or photoredox catalysis, but how do and catalysis compare? Both approaches provide access to high energy intermediates (e.g., radicals) enable bond formations not constrained by rules ionic 2 electron (e) mechanisms. Instead, they 1e mechanisms capable bypassing electronic steric limitations protecting group requirements, thus enabling chemists disconnect molecules in new different ways. However, while providing similar intermediates, differ several physical chemistry principles. Understanding those differences can be key designing transformations forging disconnections. This review aims highlight these similarities between comparing their underlying principles describing impact electrochemical photochemical methods.

Язык: Английский

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Photochemical and Electrochemical Applications of Proton-Coupled Electron Transfer in Organic Synthesis

Chemical Reviews, Год журнала: 2021, Номер 122(2), С. 2017 - 2291

Опубликована: Ноя. 23, 2021

We present here a review of the photochemical and electrochemical applications multi-site proton-coupled electron transfer (MS-PCET) in organic synthesis. MS-PCETs are redox mechanisms which both an proton exchanged together, often concerted elementary step. As such, MS-PCET can function as non-classical mechanism for homolytic bond activation, providing opportunities to generate synthetically useful free radical intermediates directly from wide variety common functional groups. introduction practitioner’s guide reaction design, with emphasis on unique energetic selectivity features that characteristic this class. then chapters oxidative N–H, O–H, S–H, C–H homolysis methods, generation corresponding neutral species. Then, reductive PCET activations involving carbonyl, imine, other X═Y π-systems, heteroarenes, where ketyl, α-amino, heteroarene-derived radicals be generated. Finally, we asymmetric catalysis materials device applications. Within each chapter, subdivide by group undergoing homolysis, thereafter type transformation being promoted. Methods published prior end December 2020 presented.

Язык: Английский

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Organic thermally activated delayed fluorescence (TADF) compounds used in photocatalysis

Chemical Society Reviews, Год журнала: 2021, Номер 50(13), С. 7587 - 7680

Опубликована: Янв. 1, 2021

Organic compounds that show Thermally Activated Delayed Fluorescence (TADF) have become wildly popular as next generation emitters in organic light-emitting diodes (OLEDs), but since 2016, received significant and increasing attention photocatalysts.

Язык: Английский

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Recent advances in visible-light-driven organic reactions

National Science Review, Год журнала: 2017, Номер 4(3), С. 359 - 380

Опубликована: Апрель 5, 2017

Abstract In recent years, visible-light-driven organic reactions have been experiencing a significant renaissance in response to topical interest environmentally friendly green chemical synthesis. The transformations using inexpensive, readily available visible-light sources come the forefront chemistry as powerful strategy for activation of small molecules. this review, we focus on advances development reactions, including aerobic oxidation, hydrogen-evolution energy-transfer and asymmetric reactions. These key research topics represent promising towards practical, scalable industrial processes with great environmental benefits.

Язык: Английский

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High‐Valent‐Cobalt‐Catalyzed C−H Functionalization Based on Concerted Metalation–Deprotonation and Single‐Electron‐Transfer Mechanisms

ChemCatChem, Год журнала: 2016, Номер 8(7), С. 1242 - 1263

Опубликована: Март 23, 2016

Abstract C−H functionalization has been established as a powerful strategy for the commercial construction of organic molecules. This review encompasses most recent advances in activation catalyzed by earth‐abundant cobalt complexes, involving two types fundamental reaction paths, that is, concerted metalation–deprotonation (CMD) path associated with non‐oxidative and intermolecular single‐electron‐transfer (SET) path. Transformations high‐valent based on mechanisms used syntheses, including those C−C C−X (X=O N) bond formation, are herein presented.

Язык: Английский

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Strategies to Generate Nitrogen-centered Radicals That May Rely on Photoredox Catalysis: Development in Reaction Methodology and Applications in Organic Synthesis

Chemical Reviews, Год журнала: 2021, Номер 122(2), С. 2353 - 2428

Опубликована: Окт. 8, 2021

For more than 70 years, nitrogen-centered radicals have been recognized as potent synthetic intermediates. This review is a survey designed for use by chemists engaged in target-oriented synthesis. summarizes the recent paradigm shift access to and application of N-centered enabled visible-light photocatalysis. broadens streamlines approaches many small molecules because photocatalysis conditions are mild. Explicit attention paid innovative advances N–X bonds radical precursors, where X = Cl, N, S, O, H. clarity, key mechanistic data noted, available. Synthetic applications limitations summarized illuminate tremendous utility photocatalytically generated radicals.

Язык: Английский

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Photocatalytic Activation of Less Reactive Bonds and Their Functionalization via Hydrogen-Evolution Cross-Couplings

Accounts of Chemical Research, Год журнала: 2018, Номер 51(10), С. 2512 - 2523

Опубликована: Окт. 3, 2018

Cross-coupling reactions have been established as potential tools for manufacture of complex molecular frameworks diversified interests by connecting two simple molecules through the formation a carbon-carbon (C-C) or carbon-heteroatom (C-X) bond. Conventional cross-couplings are transition metal-catalyzed between electrophiles and nucleophiles. Generally, electrophilic partner is an aryl alkenyl halide, nucleophile organometallic reagent, both obtained from prefunctionalization their corresponding hydrocarbons. During past decade, dehydrogenative carbon-hydrogen (C-H) bonds one C-H bond heteroatom-hydrogen (X-H) bond, which build C-C C-X linkage respectively, emerged attractive strategy in synthetic chemistry. Such straightforward couplings allow use less functionalized reagents, thus reducing number steps to target molecule minimizing waste production. However, such involve stoichiometric amounts sacrificial oxidants peroxides, high-valent metals, iodine(III) oxidants. This leads low atom economy possible generation toxic wastes. Recently, visible light photocatalytic cross-coupling received much attention due utilizing sunlight source energy making process appealing. In this approach, metal complexes, organic dyes, semiconductor quantum dots that absorb employed photocatalysts. Upon irradiation, photocatalyst initiates single electron transfer with substrate(s) generate radical cation anion substrate, undergoes desired reaction interest. case, oxygen utilized oxidant hydrogen peroxide only byproduct. These aspects make greener than reactions. Research efforts our group led development environmentally benign construct different X-H photocatalysis. Our hydrogen-evolution reactions, combines proton reduction cocatalyst create dual catalyst system. The former uses driving force cross-coupling, while latter may capture electrons substrates intermediates reduce protons eliminated reactive scaffolds (C-H/C-H C-H/X-H bonds) into (H2). Thus, without any under mild conditions, system affords products excellent yields equimolar amount H2 sole highly step economical particularly useful species sensitive oxidative conditions. Account highlights findings laboratories on featuring activation functionalization C(sp3)-H adjacent amino groups atoms ethers, aromatic C(sp2)-H bonds, several types bonds. We expect combining holds significant transformations.

Язык: Английский

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Photoredox Catalysis Unlocks Single-Electron Elementary Steps in Transition Metal Catalyzed Cross-Coupling

ACS Central Science, Год журнала: 2016, Номер 2(5), С. 293 - 301

Опубликована: Май 3, 2016

Since initial reports, cross-coupling technologies employing photoredox catalysts to access novel reactivity have developed with increasing pace. In this Outlook, prominent examples from the recent literature are organized on basis of elementary transformation enabled by catalysis and discussed in context relevant historical precedent stoichiometric organometallic chemistry. This treatment allows mechanistic similarities inherent odd-electron transition metal be generalized a set lessons for future reaction development.

Язык: Английский

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Electroorganic Synthesis under Flow Conditions

Accounts of Chemical Research, Год журнала: 2019, Номер 52(12), С. 3287 - 3296

Опубликована: Ноя. 6, 2019

Despite the long history of electroorganic synthesis, it did not participate in mainstream chemical research for a time. This is probably due to lack equipment and standardized protocols. However, nowadays organic electrochemistry witnessing renaissance, wide range interesting electrochemical transformations methodologies have been developed, only academic purposes but also large scale industrial production. Depending on source electricity, methods can be inherently green environmentally benign easily controlled achieve high levels selectivity. In addition, generation consumption reactive or unstable intermediates hazardous reagents achieved safe way. Limitations traditional batch-type such as restricted electrode surface, necessity supporting electrolytes, difficulties scaling up alleviated using flow cells. Microreactors offer surface-to-volume ratios enable precise control over temperature, residence time, rate, pressure. efficient mixing, enhanced mass heat transfer, handling small volumes lead simpler scaling-up protocols minimize safety concerns. Electrolysis under conditions reduces possibility overoxidation reaction mixture flown continuously out reactor contrast electrolysis this Account, we highlight our contributions area synthesis past decade. We designed manufactured different generations The first-generation was effectively used developing simple one-step diaryliodonium salts proof-of-concept reactions trifluoromethylation electron-deficient alkenes via Kolbe trifluoroacetic acid addition selective deprotection isonicotinyloxycarbonyl (iNoc) group from carbonates thiocarbonates. improved second-generation cell enabled development isoindolinones, benzothiazoles, thiazolopyridines, achieving gram-scale some products without changing design reoptimizing parameters. same an continuous hypervalent iodine reagents. generated were isolation various oxidative coupled flow/flow manner could transformed into bench-stable quantitative ligand exchange with appropriate acids. Our further commercialized by Vapourtec Ltd. demonstrated power online analysis accelerating optimizations methodology development. Online spectrometry fast screening charge needed cyclization amides isoindolinones. 2D-HPLC combined Design Experiments approach empowered rapid optimization stereoselective alkoxylations amino derivatives.

Язык: Английский

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