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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Arene diversification through distal C(sp ² )−H functionalization

Science, Journal Year: 2021, Volume and Issue: 372(6543)

Published: May 13, 2021

Transition metal-catalyzed aryl C-H activation is a powerful synthetic tool as it offers step and atom-economical routes to site-selective functionalization. Compared with proximal ortho-C-H activation, distal (meta- and/or para-) remains more challenging due the inaccessibility of these sites in formation energetically favorable organometallic pretransition states. Directing catalyst toward bonds requires judicious template engineering design, well prudent choice ligands. This review aims summarize recent elegant discoveries exploiting directing group assistance, transient mediators or traceless directors, noncovalent interactions, ligand selection control activation.

Language: Английский

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Recent development in transition metal-catalysed C–H olefination

Chemical Science, Journal Year: 2021, Volume and Issue: 12(8), P. 2735 - 2759

Published: Jan. 1, 2021

Transition metal-catalysed functionalizations of inert C-H bonds to construct C-C represent an ideal route in the synthesis valuable organic molecules. Fine tuning directing groups, catalysts and ligands has played a crucial role selective bond (sp2 or sp3) activation. Recent developments these areas have assured high level regioselectivity olefination reactions. In this review, we summarized recent progress oxidative sp2 sp3 with special emphasis on distal, atroposelective, non-directed directed olefination. The scope, limitation, mechanism various transition reactions been described briefly.

Language: Английский

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Flow Rhodaelectro-Catalyzed Alkyne Annulations by Versatile C–H Activation: Mechanistic Support for Rhodium(III/IV)

Journal of the American Chemical Society, Journal Year: 2019, Volume and Issue: 141(43), P. 17198 - 17206

Published: Sept. 24, 2019

A flow-metallaelectro-catalyzed C–H activation was realized in terms of robust rhodaelectro-catalyzed alkyne annulations. To this end, a modular electro-flow cell with porous graphite felt anode designed to ensure efficient turnover. Thereby, variety C–H/N–H functionalizations proved amenable for annulations high levels regioselectivity and functional group tolerance, viable both an inter- or intramolecular manner. The allowed easy scale up, while in-operando kinetic analysis accomplished by online flow-NMR spectroscopy. Mechanistic studies suggest oxidatively induced reductive elimination pathway on rhodium(III) electrocatalytic regime.

Language: Английский

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Para-Selective C–H Borylation of Common Arene Building Blocks Enabled by Ion-Pairing with a Bulky Countercation

Journal of the American Chemical Society, Journal Year: 2019, Volume and Issue: 141(39), P. 15477 - 15482

Published: Aug. 5, 2019

The selective functionalization of C–H bonds at the arene para position is highly challenging using transition metal catalysis. Iridium-catalyzed borylation has emerged as a leading technique for functionalization, but there are only handful strategies para-selective borylation, which operate on specific substrate classes and use bespoke ligands or catalysts. We describe remarkably general protocol results in para-selectivity some most common building blocks (anilines, benzylamines, phenols, benzyl alcohols) uses standard ligands. Our strategy hinges upon facile conversion substrates into sulfate sulfamate salts, wherein anionic component paired with tetrabutylammonium cation. hypothesize that bulk this cation disfavors meta-C–H thereby promoting reaction.

Language: Английский

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Hydroarylation of Alkenes Using Anilines in Hexafluoroisopropanol

ACS Catalysis, Journal Year: 2020, Volume and Issue: 10(11), P. 6023 - 6029

Published: May 5, 2020

Providing new methods for the selective functionalization of small molecules is highly desirable, because installing molecular diversity in a desired position, example, allows one to modulate bioactive molecules. This work reports method anilines using hexafluoroisopropanol (HFIP) as solvent promote an acid-catalyzed hydroarylation olefins. Mechanistic experiments revealed that HFIP both protonates alkene and selectively enables toward electrophilic aromatic substitution. powerful strategy has been applied anti-inflammatory mefenamic acid with chemocontrol regiocontrol.

Language: Английский

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Reactivity-Controlling Factors in Carboxylate-Assisted C–H Activation under 4d and 3d Transition Metal Catalysis

ACS Catalysis, Journal Year: 2020, Volume and Issue: 10(18), P. 10551 - 10558

Published: Aug. 17, 2020

Detailed density functional theory calculations provide valuable insight into reactivity-controlling factors in transition metal-catalyzed C–H activation by carboxylate assistance. The chelation-assisted of a variety arenes 3d and 4d metal complexes was analyzed means bond order analysis through (DFT) as well energy decomposition DLPNO–CCSD(T) calculations, thereby providing in-depth information on distinct electronic influences the key state demonstrating preferred base-assisted internal electrophilic substitution (BIES) rather than concerted metalation-deprotonation (CMD) pathway.

Language: Английский

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Sterically Controlled Late-Stage C–H Alkynylation of Arenes

Journal of the American Chemical Society, Journal Year: 2019, Volume and Issue: 141(47), P. 18662 - 18667

Published: Nov. 12, 2019

Phenylacetylenes are key structural motifs in organic chemistry, which find widespread applications bioactive molecules, synthetic intermediates, functional materials, and reagents. These molecules typically prepared from prefunctionalized starting e.g. using the Sonogashira coupling, or directing group-based C–H activation strategies. While highly efficient, these approaches remain limited by their inherent selectivities for specific regioisomers. Herein we present a complementary approach based on an arene-limited nondirected activation. The reaction is predominantly controlled steric rather than electronic factors thereby gives access to product spectrum with respect traditional methods. A broad scope as well suitability of this protocol late-stage functionalization demonstrated.

Language: Английский

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C−H Oxygenation Reactions Enabled by Dual Catalysis with Electrogenerated Hypervalent Iodine Species and Ruthenium Complexes

Angewandte Chemie International Edition, Journal Year: 2019, Volume and Issue: 59(8), P. 3184 - 3189

Published: Nov. 28, 2019

The catalytic generation of hypervalent iodine(III) reagents by anodic electrooxidation was orchestrated towards an unprecedented electrocatalytic C-H oxygenation weakly coordinating aromatic amides and ketones. Thus, quantities iodoarenes in concert with amounts ruthenium(II) complexes set the stage for versatile activations ample scope high functional group tolerance. Detailed mechanistic studies experiment computation substantiate role iodoarene as electrochemically relevant species oxygenations electricity a sustainable oxidant molecular hydrogen sole by-product. para-Selective likewise proved viable absence directing groups.

Language: Английский

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C7‐Indole Amidations and Alkenylations by Ruthenium(II) Catalysis

Angewandte Chemie International Edition, Journal Year: 2020, Volume and Issue: 59(30), P. 12534 - 12540

Published: June 2, 2020

C7-H-functionalized indoles are ubiquitous structural units of biological and pharmaceutical compounds for numerous antiviral agents against SARS-CoV or HIV-1. Thus, achieving site-selective functionalizations the C7-H position indoles, while discriminating among other bonds, is in high demand. Herein, we disclose activations by ruthenium(II) biscarboxylate catalysis under mild conditions. Base-assisted internal electrophilic-type substitution C-H ruthenation weak O-coordination enabled functionalization offered a broad scope, including C-N C-C bond formation. The versatile ruthenium-catalyzed were characterized gram-scale syntheses traceless removal directing group, thus providing easy access to pharmaceutically relevant scaffolds. Detailed mechanistic studies through spectroscopic spectrometric analyses shed light on unique nature robust ruthenium indoles.

Language: Английский

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