Palladium-Catalyzed [3 + 2] Annulation of Aromatic Amides with Maleimides through Dual C–H Activation

Organic Letters, Journal Year: 2023, Volume and Issue: 25(13), P. 2190 - 2195

Published: March 26, 2023

A palladium-catalyzed [3 + 2] annulation of substituted aromatic amides with maleimides providing tricyclic heterocyclic molecules in good to moderate yields through weak carbonyl chelation is reported. The reaction proceeds via a dual C-H bond activation where the first takes place selectively at benzylic position followed by second meta afford five-membered cyclic ring. An external ligand Ac-Gly-OH has been used succeed this protocol. plausible mechanism proposed for reaction.

Language: Английский

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Air‐Stable Bis‐Cyclometallated Iridium Catalysts for Ortho‐Directed C(sp²)−H Borylation

Advanced Synthesis & Catalysis, Journal Year: 2024, Volume and Issue: 366(10), P. 2292 - 2304

Published: March 21, 2024

Abstract We report a class of isolable bis‐cyclometallated iridium precatalysts (ImIr) and their use in regioselective ortho −C−H borylation aromatic, heteroaromatic, acrylic, aliphatic systems. The catalysts consist two imine ligands an acetate coordinated to (III) center. character ImIr warrants its compatibility with high‐throughput experimentation, prerequisite for applications late‐stage functionalization (LSF) complex substrates. Initial mechanistic studies point towards inner‐sphere mechanism involving species shedding light on the general understanding ‐selective C−H borylations.

Language: Английский

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Cobalt catalyzed practical hydroboration of terminal alkynes with time-dependent stereoselectivity

Nature Communications, Journal Year: 2024, Volume and Issue: 15(1)

Published: March 12, 2024

Abstract Stereodefined vinylboron compounds are important organic synthons. The synthesis of E −1-vinylboron typically involves the addition a B-H bond to terminal alkynes. selective generation thermodynamically unfavorable Z -isomers remains challenging, necessitating improved methods. Here, such proficient and cost-effective catalytic system is introduced, comprising cobalt salt readily accessible air-stable CNC pincer ligand. This enables transformation alkynes, even in presence bulky substituents, with excellent -selectivity. High turnover numbers (>1,600) frequencies (>132,000 h −1 ) achieved at room temperature, reaction can be scaled up 30 mmol smoothly. Kinetic studies reveal formal second-order dependence on concentration. Mechanistic investigations indicate that alkynes exhibit higher affinity for catalyst than alkene products, resulting exceptional -selective performance. Furthermore, rare time-dependent stereoselectivity observed, allowing quantitative conversion -vinylboronate esters -isomers.

Language: Английский

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Selective Borylation of C(sp³)−H Bond of Methyl Ethers Catalyzed by Iron Complexes Bearing Anionic Benzene‐Based PCP‐Pincer Ligands

ChemistryEurope, Journal Year: 2025, Volume and Issue: unknown

Published: Jan. 28, 2025

Abstract Highly selective catalytic C(sp 3 )−H borylation of methoxy groups has been achieved using newly synthesized iron complexes bearing benzene‐based PCP‐type pincer ligands as catalysts. Reactions various aryl and alkyl methyl ethers substrates with bis(pinacolato)diboron under mild reaction conditions proceeded to afford the corresponding borylated products in good high yields. A successful example iron‐catalyzed a methylene group tetrahydrofuran (THF) was also presented. plausible pathway is proposed based on experimental result some stoichiometric reactions DFT calculations model reaction, where iron‐boryl ‐alkyl may work key intermediates.

Language: Английский

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Organopotassium‐Catalyzed Silylation of Benzylic C(sp³)−H Bonds

Angewandte Chemie International Edition, Journal Year: 2023, Volume and Issue: 62(31)

Published: June 7, 2023

Benzylsilanes have found increasing applications in organic synthesis as bench-stable synthetic intermediates, yet are mostly produced by stoichiometric procedures. Catalytic alternatives based on the atom-economical silylation of benzylic C(sp3 )-H bonds remain scarcely available specialized directing groups and catalytic systems needed to outcompete kinetically-favored C(sp2 bonds. Herein, we describe first general catalytic-in-metal undirected under ambient, transition metal-free conditions using stable tert-butyl-substituted silyldiazenes (tBu-N=N-SiR3 ) silicon source. The high activity selectivity system, exemplified preparation various mono- or gem-bis benzyl(di)silanes, originates from facile generation organopotassium reagents, including tert-butylpotassium.

Language: Английский

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Cobalt-catalyzed double hydroboration of pyridines

Chemical Science, Journal Year: 2024, Volume and Issue: 15(14), P. 5201 - 5210

Published: Jan. 1, 2024

Cobalt(ii) complexes were prepared from a modular phosphinopyridonate platform and applied to the hydroboration of pyridines. The synthetically useful, yet challenging, double toward tetrahydropyridine derivatives was successfully performed with high activity regiocontrol. This new method enabled direct synthesis N-heterocyclic allylic boronates commercial pyridines pinacolborane (HBpin). One-pot acetylation afforded bench-stable borylated N-acetyl tetrahydropyridines in good yields. synthetic utility this procedure demonstrated by gram-scale hydroboration-acetylation sequence followed chemical diversification. Mechanistic experiments indicated metal-ligand cooperativity involving ligand-centered C-H activation intermediacy cobalt(iii) hydride species.

Language: Английский

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Building Square Planar Cobalt (II) Complexes via Sodium Mediated Cobaltation of Fluoroarenes

Angewandte Chemie International Edition, Journal Year: 2022, Volume and Issue: 61(49)

Published: Oct. 1, 2022

While cobalt complexes have already shown their potential for C-H and C-F bond activation of fluoroarenes, reactivity as metalating agents via Co-H exchange towards these substrates has not been explored. Herein, we report a Co(HMDS)2 [HMDS=N(SiMe3 )2 ] system which, when synergistically enhanced sodium amide Na(HMDS) mediation, can render chemo- regioselective cobaltation series fluoroarenes to produce new class homoleptic square planar [Na2 CoAr4 complexes. Density functional theory calculations elucidate the key roles Na/Co counterparts in stepwise sodiation/cobalt transmetalation process, leading this novel metalation. Depending on reaction stoichiometry, process occur inter- or intramolecularly, furnishing transient [NaCo(HMDS)2 Ar] intermediates which undergo ligand rearrangement afford with concomitant formation [NaCo(HMDS)3 ].

Language: Английский

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Selective Benzylic CH‐Borylations by Tandem Cobalt Catalysis

Angewandte Chemie International Edition, Journal Year: 2021, Volume and Issue: 61(1)

Published: Oct. 1, 2021

Metal-catalyzed C-H activations are environmentally and economically attractive synthetic strategies for the construction of functional molecules as they obviate need pre-functionalized substrates minimize waste generation. Great challenges reside in control selectivities, utilization unbiased hydrocarbons, operation atom-economical dehydrocoupling mechanisms. An especially mild borylation benzylic CH bonds was developed with ligand-free pre-catalyst Co[N(SiMe

Language: Английский

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Iron‐Catalysed C(sp²)‐H Borylation with Expanded Functional Group Tolerance^†

Chinese Journal of Chemistry, Journal Year: 2022, Volume and Issue: 40(24), P. 2875 - 2881

Published: Sept. 7, 2022

Comprehensive Summary Arene C(sp 2 )‐H bond borylation offers direct and efficient access to aryl boronic esters. Using in situ catalyst activation photoirradiation, the iron‐catalysed reaction of carboarenes, pyrroles, indoles has been developed using only bench‐stable pre‐catalysts reagents. Good functional group tolerance was observed including those not reported previous methods (ArNH , ArOH, ArSiR 3 ArP(O)(OR) ArC(O)NR ). Mechanistic studies revealed reductive deoxygenation, C—F protodefluorination, a demethylation methyl ethers by C—O sigma hydroboration.

Language: Английский

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Organopotassium‐Catalyzed Silylation of Benzylic C(sp³)−H Bonds

Angewandte Chemie, Journal Year: 2023, Volume and Issue: 135(31)

Published: June 7, 2023

Abstract Benzylsilanes have found increasing applications in organic synthesis as bench‐stable synthetic intermediates, yet are mostly produced by stoichiometric procedures. Catalytic alternatives based on the atom‐economical silylation of benzylic C( sp 3 )−H bonds remain scarcely available specialized directing groups and catalytic systems needed to outcompete kinetically‐favored 2 bonds. Herein, we describe first general catalytic‐in‐metal undirected under ambient, transition metal‐free conditions using stable tert ‐butyl‐substituted silyldiazenes ( t Bu−N=N−SiR ) silicon source. The high activity selectivity system, exemplified preparation various mono‐ or gem ‐bis benzyl(di)silanes, originates from facile generation organopotassium reagents, including ‐butylpotassium.

Language: Английский

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