Insights into Cobalta(III/IV/II)‐Electrocatalysis: Oxidation‐Induced Reductive Elimination for Twofold C−H Activation

Angewandte Chemie International Edition, Journal Year: 2020, Volume and Issue: 59(27), P. 10955 - 10960

Published: March 10, 2020

Abstract The merger of cobalt‐catalyzed C−H activation and electrosynthesis provides new avenues for resource‐economical molecular syntheses, unfortunately their reaction mechanisms remain poorly understood. Herein, we report the identification full characterization electrochemically generated high‐valent cobalt(III/IV) complexes as crucial intermediates in electrochemical oxygenations. Detailed mechanistic studies provided support an oxidatively‐induced reductive elimination via highly‐reactive cobalt(IV) intermediates. These key insights set stage unprecedented cobaltaelectro two‐fold C−H/C−H activation.

Language: Английский

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Implementation of Cooperative Designs in Polarized Transition Metal Systems—Significance for Bond Activation and Catalysis

ACS Catalysis, Journal Year: 2020, Volume and Issue: 10(23), P. 14024 - 14055

Published: Nov. 17, 2020

Bond activation and catalysis are central to the development of a sustainable energy system. Frustrated Lewis Pairs have conceptually revolutionized inert chemical bonds. Far less developed hybrid systems containing at least one transition metal as part electron-donating/accepting composition. These cooperative architectures present advantages over traditional systems. For instance, they incorporate, concept FLPs, movement electron pairs typically encountered in elementary steps organometallic catalysis. This Perspective presents arguably most relevant recent progress vivid field research that aspires implement designs polarized Moreover, it provides tools for future developments shows molecular control bond-making -breaking processes can be achieved.

Language: Английский

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Palladium-Catalyzed Nondirected Late-Stage C–H Deuteration of Arenes

Journal of the American Chemical Society, Journal Year: 2021, Volume and Issue: 143(40), P. 16370 - 16376

Published: Sept. 28, 2021

We describe a palladium-catalyzed nondirected late-stage deuteration of arenes. Key aspects include the use D2O as convenient and easily available deuterium source discovery highly active N,N-bidentate ligands containing an N-acylsulfonamide group. The reported protocol enables high degrees incorporation via reversible C–H activation step features extraordinary functional group tolerance, allowing for complex substrates. This is exemplified by isotopic labeling various pharmaceutically relevant motifs related scaffolds. expect that this method, among other applications, will prove useful tool in drug development processes mechanistic studies.

Language: Английский

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Dual Ligand Enabled Nondirected C–H Chalcogenation of Arenes and Heteroarenes

Journal of the American Chemical Society, Journal Year: 2022, Volume and Issue: 144(27), P. 12032 - 12042

Published: June 27, 2022

Chalcogenide motifs are present as principal moieties in a vast array of natural products and complex molecules. Till date, the construction these chalcogen has been restricted to either use directing groups or employment large excess electronically activated arenes, typically employed cosolvent. Despite being highly effective, methods have their own limitations step economy deployment an amount arenes. Herein, we report evolution catalytic system employing arene-limited, nondirected thioarylation arenes heteroarenes using complimentary dual-ligand approach. The reaction is controlled by combination steric electronic factors, utilization suitable ligand enables generation on spectrum that generated classical methods. ligands remains imperative protocol with theoretical calculations pointing towards monoprotected amino acid crucial concerted metalation deprotonation (CMD) mechanism characteristic [5,6]-palladacyclic transition state, while pyridine moiety assists active catalyst species formation product release. Combined experimental computational mechanistic investigations point toward C–H activation both regio- rate-determining. Interestingly, oxidative addition diphenyl disulfide substrate found be unlikely, alternative transmetalation-like involving Pd–Ag heterometallic proposed operative.

Language: Английский

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Dual-Ligand Catalyst for the Nondirected C–H Olefination of Heteroarenes

Journal of the American Chemical Society, Journal Year: 2023, Volume and Issue: 145(14), P. 8198 - 8208

Published: March 28, 2023

Pd(II)-catalyzed nondirected C-H functionalization of heteroarenes is a significant challenge for the following reasons: poor reactivity electron-deficient heterocycles and unproductive coordination Lewis basic nitrogen atoms. Existing methodologies using palladium catalysis often employ large excess heterocycle substrates to overcome these hurdles. Despite recent advances in arenes that allow them be used as limiting reagents, reaction conditions are incompatible with heteroarenes. Herein we report dual-ligand catalyst enables olefination without substrate. In general, use 1-2 equiv was sufficient obtain synthetically useful yields. The rationalized by synergy between two types ligands: bidentate pyridine-pyridone ligand promotes cleavage; monodentate substrate acts second form cationic Pd(II) complex has high affinity arenes. proposed cooperation supported combination X-ray, kinetics, control experiments.

Language: Английский

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Controlling Reactivity and Selectivity in the Nondirected C–H Activation of Arenes with Palladium

Accounts of Chemical Research, Journal Year: 2023, Volume and Issue: 56(18), P. 2459 - 2472

Published: Aug. 24, 2023

ConspectusAromatic structures are widespread motifs throughout organic chemistry, and C-H activation has been recognized as a major tool for enabling their sustainable efficient functionalization. Through activation, arenes can be modified without the need prefunctionalization, leading to inherent atom- step-economic advantages over traditional methods. However, development of synthetically useful methods, several hurdles have overcome. The strength bonds necessitates sufficiently reactive catalysts, while presence multiple within substrate poses challenges in terms site-selectivity. Traditionally these addressed by control. By attaching different directing groups (DGs), reactivity respective arene was significantly enhanced DG guided metal close proximity specific bonds, resulting high introduction removal add additional steps synthetic sequence, scope reaction is limited class. complementary nondirected methods that applied broad range necessity carry functional group coordinates Pd (referred simple arenes) therefore highly desirable. intrinsically lower such substrates absence selectivity-determining pose significant solved only catalysts. Consequently, field especially with respect Pd-catalyzed remained comparatively underdeveloped when we initiated our research program 2017. At time, state-of-the-art required used large excess, precluding its use late-stage Since organopalladium species among most versatile intermediates, realized developing system, which effectively selectively activate limiting reagent, would powerful chemistry. This account summarizes groups' toward application catalytic systems offering this desired focuses explicitly on functionalization reactions arenes, where employed reagent. After an state before 2017 associated challenges, experimental mechanistic details about first arene-limited, palladium will discussed. enabled identification combination two ligands, N-heterocycle amino acid-derived ligand. Afterward discuss expansion dual-ligand approach further arene-limited transformations. Finally, describe methodologies originated from observations made during studies, namely, deuteration selective olefination method uses noncovalent interactions induce meta selectivity.

Language: Английский

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Azaruthena(II)‐bicyclo[3.2.0]heptadiene: Key Intermediate for Ruthenaelectro(II/III/I)‐catalyzed Alkyne Annulations

Angewandte Chemie International Edition, Journal Year: 2020, Volume and Issue: 59(27), P. 11130 - 11135

Published: March 4, 2020

A ruthenium-catalyzed electrochemical dehydrogenative annulation reaction of imidazoles with alkynes has been established, enabling the preparation various bridgehead N-fused [5,6]-bicyclic heteroarenes through regioselective C-H/N-H without chemical metal oxidants. Novel azaruthenabicyclo[3.2.0]heptadienes were fully characterized and identified as key intermediates. Mechanistic studies are suggestive an oxidatively induced reductive elimination pathway within a ruthenium(II/III) regime.

Language: Английский

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Ligand‐Enabled γ‐C(sp³)−H Olefination of Free Carboxylic Acids

Angewandte Chemie International Edition, Journal Year: 2020, Volume and Issue: 59(31), P. 12848 - 12852

Published: April 6, 2020

We report the ligand-enabled C-H activation/olefination of free carboxylic acids in γ-position. Through an intramolecular Michael addition, δ-lactones are obtained as products. Two distinct ligand classes identified that enable challenging palladium-catalyzed activation The developed protocol features a wide range acid substrates and olefin reaction partners is shown to be applicable on preparatively useful scale. Insights into underlying mechanism through kinetic studies reported.

Language: Английский

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meta‐Selective C−H Arylation of Fluoroarenes and Simple Arenes

Angewandte Chemie International Edition, Journal Year: 2020, Volume and Issue: 59(33), P. 13831 - 13835

Published: April 25, 2020

Fluorine is known to promote ortho-C-H metalation. Based upon this reactivity, we employed an activated norbornene that traps the ortho-palladation intermediate and then relayed meta position, leading meta-selective C-H arylation of fluoroarenes. Deuterium experiment suggests meta-arylation initiated by ortho activation catalytic cycle terminated C-2 protonation. A dual-ligand system crucial for observed high reactivity site selectivity. Applying approach simple benzene or other arenes also affords products with good yield

Language: Английский

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Cobalta-Electrocatalyzed C–H Allylation with Unactivated Alkenes

ACS Catalysis, Journal Year: 2020, Volume and Issue: 10(11), P. 6457 - 6462

Published: May 12, 2020

Versatile and robust cobalt catalysis enabled the electrochemical C–H allylation with nonactivated alkenes. In contrast to precious palladium, rhodium, iridium, ruthenium catalysts that are limited electronically activated styrenes acrylates, we herein disclose cobalt-catalyzed electro-oxidative allylations Thus, allylated benzamides were obtained high levels of chemoselectivity, positional selectivity, regioselectivity in biomass-derived solvent γ-valerolactone. Detailed mechanistic studies provided strong support for a base-assisted internal electrophilic-type substitution mechanism key activation step. The cobaltaelectro-catalysis overall achieved resource-economy by avoiding use stoichiometric chemical oxidants, H2 as only byproduct.

Language: Английский

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