3d Transition Metals for C–H Activation

Chemical Reviews, Journal Year: 2018, Volume and Issue: 119(4), P. 2192 - 2452

Published: Nov. 27, 2018

C–H activation has surfaced as an increasingly powerful tool for molecular sciences, with notable applications to material crop protection, drug discovery, and pharmaceutical industries, among others. Despite major advances, the vast majority of these functionalizations required precious 4d or 5d transition metal catalysts. Given cost-effective sustainable nature earth-abundant first row metals, development less toxic, inexpensive 3d catalysts gained considerable recent momentum a significantly more environmentally-benign economically-attractive alternative. Herein, we provide comprehensive overview on until summer 2018.

Language: Английский

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Mild metal-catalyzed C–H activation: examples and concepts

Chemical Society Reviews, Journal Year: 2016, Volume and Issue: 45(10), P. 2900 - 2936

Published: Jan. 1, 2016

C–H Activation reactions that proceed under mild conditions are more attractive for applications in complex molecule synthesis. Mild transformations reported since 2011 reviewed and the different concepts strategies have enabled their mildness discussed.

Language: Английский

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Substrate Activation Strategies in Rhodium(III)-Catalyzed Selective Functionalization of Arenes

Accounts of Chemical Research, Journal Year: 2015, Volume and Issue: 48(4), P. 1007 - 1020

Published: April 6, 2015

The possibility of developing new methods for the efficient construction organic molecules via disconnections other than traditional functional group transformations has driven interest in direct functionalization C-H bonds. ubiquity bonds makes such attractive, but they also pose several challenges. first is reactivity and selectivity To achieve this, directing groups (DGs) are often installed that can enhance effective concentration catalyst, leading to thermodynamically stable metallacyclic intermediates. However, presence a pendant product undesirable unnecessary. This may account limitation applications reactions more common general uses. Thus, development removable or functionalizable desirable. Another key problem resulting M-C bond be low, which limit scope coupling partners hence reaction patterns activation reactions. While Cp*Rh(III)-catalyzed arenes was reported only 7 years ago, significant progress been made this area past few years. We began our studies 2010, we others have demonstrated diversified catalytic realized using Cp*Rh(III) complexes with high reactivity, stability, compatibility. Account describes efforts solve some these challenges Rh(III) catalysis. fulfilled design arene substrates by taking advantage nucleophilicity, electrophilicity, oxidizing potential, properties participating ligand when coupled relatively reactive unsaturated as alkenes alkynes. These situ funtionalizable roles DG allowed extensive chemical manipulation initial product, especially diverse array heterocycles. In polar partners, Rh(III)-C(aryl) showed higher both an organometallic reagent nucleophilic aryl source. were accordingly activated virtue umpolung, ring strain, rearomatization. All possible integration compatibility Rh(III)-C into systems. date achieved under rhodium addition, means stoichiometric reactions, gained mechanistic insights interactions between Rh-C opened avenues future

Language: Английский

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C–H Activation: Toward Sustainability and Applications

ACS Central Science, Journal Year: 2021, Volume and Issue: 7(2), P. 245 - 261

Published: Feb. 2, 2021

Since the definition of "12 Principles Green Chemistry" more than 20 years ago, chemists have become increasingly mindful need to conserve natural resources and protect environment through judicious choice synthetic routes materials. The direct activation functionalization C–H bonds, bypassing intermediate functional group installation is, in abstracto, step atom economic, but numerous factors still hinder sustainability large-scale applications. In this Outlook, we highlight research areas seeking overcome challenges activation: pursuit abundant metal catalysts, avoidance static directing groups, replacement oxidants, introduction bioderived solvents. We close by examining progress made subfield aryl borylation from its origins, highly efficient precious Ir-based systems, emerging 3d catalysts. future growth field will depend on industrial uptake, thus urge researchers strive toward sustainable activation.

Language: Английский

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Key Green Chemistry research areas from a pharmaceutical manufacturers’ perspective revisited

Green Chemistry, Journal Year: 2018, Volume and Issue: 20(22), P. 5082 - 5103

Published: Jan. 1, 2018

The ACS Green Chemistry Institute® Pharmaceutical Roundtable has assembled an updated list of key research areas to highlight transformations and reaction media where more sustainable technologies would be most impactful.

Language: Английский

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Metal‐Catalyzed Annulations through Activation and Cleavage of C−H Bonds

Angewandte Chemie International Edition, Journal Year: 2016, Volume and Issue: 55(37), P. 11000 - 11019

Published: June 22, 2016

The exponential increase in the number of catalytic transformations that involve a metal-promoted activation hitherto considered inert C-H bonds is promoting fundamental change field synthetic chemistry. Although most reactions involving activations consist simple functionalizations or additions, recent years have witnessed an upsurge related can be formally as cycloaddition processes. These are particularly appealing from perspective because they allow conversion readily available substrates into highly valuable cyclic products rapid and sustainable manner. In many cases, these annulations formation metallacyclic intermediates resemble those proposed for standard metal-catalyzed cycloadditions unsaturated precursors.

Language: Английский

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(Pentamethylcyclopentadienyl)cobalt(III)‐Catalyzed C–H Bond Functionalization: From Discovery to Unique Reactivity and Selectivity

Advanced Synthesis & Catalysis, Journal Year: 2017, Volume and Issue: 359(8), P. 1245 - 1262

Published: March 16, 2017

Abstract High‐valent (pentamethylcyclopentadienyl)cobalt(III) [Cp*Co(III)] catalysts were found as inexpensive alternatives to (pentamethylcyclopentadienyl)rhodium(III) [Cp*Rh(III)] in the field of C—H bond functionalization, and applied a variety transformations. In this review, after discovery early examples Cp*Co(III)‐catalyzed functionalization are summarized, unique reactivity selectivity Cp*Co(III) differences between cobalt rhodium catalysis intensively discussed. Such assumed be caused by lower electronegativity, hard nature, smaller ionic radius cobalt. magnified image

Language: Английский

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Merging Visible Light Photoredox Catalysis with Metal Catalyzed C–H Activations: On the Role of Oxygen and Superoxide Ions as Oxidants

Accounts of Chemical Research, Journal Year: 2016, Volume and Issue: 49(9), P. 1969 - 1979

Published: Aug. 24, 2016

The development of efficient catalytic systems for direct aromatic C-H bond functionalization is a long-desired goal chemists, because these protocols provide environmental friendly and waste-reducing alternatives to classical methodologies C-C C-heteroatom formation. A key challenge transformations the reoxidation in situ generated metal hydride or low-valent complexes primary forming cycle. To complete cycle regenerate activation catalyst, (super)stoichiometric amounts Cu(II) Ag(I) salts have often been applied. Recently, "greener" approaches developed by applying molecular oxygen combination with salts, internal oxidants that are cleaved during reaction, solvents additives enabling reoxidation. All improved friendliness but not overcome obstacles associated overall limited functional group substrate tolerance. Hence, processes do feature unfavorable aspects described above products streamlined as well economically ecologically advantageous manner would be desirable. In this context, we decided examine visible light photoredox catalysis new alternative conventionally applied regeneration/oxidation procedures. This Account summarizes our recent advances expanding area will highlight concept merging distinct redox functionalizations through application catalysis. Photoredox can considered electron-donating -accepting processes, making use visible-light absorbing homogeneous heterogeneous metal-based catalysts, organic dye sensitizers polymers. As consequence, is, principle, an ideal tool recycling any given catalyst via coupled electron transfer (ET) process. Here describe first successful endeavors address challenges combining different ruthenium, rhodium, palladium catalyzed activations. Since only small oxidant immediately consumed transformations, side reactions substrates avoided. Thus, usually oxidant-sensible used, which makes methods highly suitable complex structure syntheses. Moreover, mechanistic studies shed on reaction pathways, intermediates, species. dual concept, consisting combined functionalization, provides many opportunities further explorations field functionalization.

Language: Английский

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Rhodium-Catalyzed C–H Activation of Phenacyl Ammonium Salts Assisted by an Oxidizing C–N Bond: A Combination of Experimental and Theoretical Studies

Journal of the American Chemical Society, Journal Year: 2015, Volume and Issue: 137(4), P. 1623 - 1631

Published: Jan. 8, 2015

Rh(III)-catalyzed C–H activation assisted by an oxidizing directing group has evolved to a mild and redox-economic strategy for the construction of heterocycles. Despite success, these coupling systems are currently limited cleavage N–O or N–N bond. Cleavage C–N bond, which allows complementary carbocycle synthesis, is unprecedented. In this article, α-ammonium acetophenones with bond have been designed as substrates under redox-neutral conditions. The α-diazo esters afforded benzocyclopentanones, unactivated alkenes such styrenes aliphatic olefins gave ortho-olefinated acetophenoes. both reactions proceeded broad scope, high efficiency, functional tolerance. Moreover, efficient one-pot diazo realized starting from α-bromoacetophenones triethylamine. reaction mechanism studied combination experimental theoretical methods. particular, three distinct mechanistic pathways scrutinized DFT studies, revealed that occurs via C-bound enolate-assisted concerted metalation–deprotonation rate-limiting. subsequent C–C formation steps, lowest energy pathway involves two rhodium carbene species key intermediates.

Language: Английский

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A Visible‐Light‐Driven Iminyl Radical‐Mediated C−C Single Bond Cleavage/Radical Addition Cascade of Oxime Esters

Angewandte Chemie International Edition, Journal Year: 2017, Volume and Issue: 57(3), P. 738 - 743

Published: Dec. 7, 2017

Abstract A room‐temperature, visible‐light‐driven N‐centered iminyl radical‐mediated and redox‐neutral C−C single bond cleavage/radical addition cascade reaction of oxime esters unsaturated systems has been accomplished. The strategy tolerates a wide range O‐acyl oximes systems, such as alkenes, silyl enol ethers, alkynes, isonitrile, enabling highly selective formation various chemical bonds. This method thus provides an efficient approach to diversely substituted cyano‐containing ketones, carbocycles, heterocycles.

Language: Английский

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