Ruthenium-Catalyzed Remote C–H Sulfonylation of <i>N</i>-Aryl-2-aminopyridines with Aromatic Sulfonyl Chlorides

Ramesh, Balu; Jeganmohan, Masilamani

doi:10.1021/acs.orglett.7b03051

Cited by 44 publications

(16 citation statements)

References 61 publications

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“…In 2017, Jeganmohan reported on unusual ruthenium-catalyzed para-C-H sulfonylations of pyridylanilines 153 with sulfonyl chloride 100a (Scheme 48). 77 In contrast to earlier studies, the transformation exclusively occurred at the C-5 position of the pyridine motif. Although the N-aryl substituent was found to be required for the reaction to proceed, a variety of substituted pyridylanilies and sulfonyl chlorides was smoothly converted to the desired products.…”

Section: Para-c-h Functionalizationscontrasting

confidence: 66%

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Remote C–H Functionalizations by Ruthenium Catalysis

Korvorapun¹,

Samanta²,

Rogge³

et al. 2021

Synthesis

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Synthetic transformations of otherwise inert C–H bonds have emerged as a powerful tool for molecular modifications during the last decades, with broad applications towards pharmaceuticals, material sciences and crop protection. Consistently, a key challenge in C–H activation chemistry is the full control of site-selectivity. In addition to substrate control through steric hindrance or kinetic acidity of C–H bonds, one important approach for the site-selective C–H transformation of arenes is the use of chelation-assistance through directing groups, therefore leading to proximity-induced ortho-C–H metalation. In contrast, more challenging remote C–H activations at the meta- or para-positions continue to be scarce. Within this review, we demonstrate the distinct character of ruthenium catalysis for remote C–H activations until March 2021, highlighting among others late-stage modifications of bio-relevant molecules. Moreover, we highlight important mechanistic insights by experiments and computation, highlighting the key importance of carboxylate-assisted C–H activation with ruthenium(II) complexes.

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Section: Para-c-h Functionalizationscontrasting

confidence: 66%

“…76 In 2017, Jeganmohan reported on unusual rutheniumcatalyzed para-C-H sulfonylations of pyridylanilines 153 with TsCl (100a) (Scheme 48). 77 In contrast to earlier studies, the transformation exclusively occurred at the C-5 position of the pyridine motif. Although the N-aryl substituent…”

Section: K Korvorapun Et Alcontrasting

confidence: 66%

Remote C–H Functionalizations by Ruthenium Catalysis

Korvorapun¹,

Samanta²,

Rogge³

et al. 2021

Synthesis

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“…Therefore [( η 6 ‐arene)MCl 2 ] 2 and [Cp # MCl 2 ] 2 (arene: η 6 ‐C 6 H 6 , p ‐cymene; Cp # : η 5 ‐C 5 H 5 , η 5 ‐C 5 Me 5 ; M: Co, Ir, Rh, Ru) are often utilized as the metal precursors to prepare diverse half‐sandwich transition‐metal complexes due to the following reasons: (i) the transition metal precursors [Cp # MCl 2 ] 2 (M = Co, Ir, Rh, Ru) are easily synthesized with high yields by reactions of metal chlorides with conjugated ligands; (ii) The hemisphere of the metal center is perfectly shielded by the Cp # ligands, minimizing the possibility of undesired side‐reactions; (iii) The redox property and solubility of these transition metal complexes is enhanced by introducing various types of substituents to cyclopentadienyl ring . Among different types of reported half‐sandwich late transition metal complexes, ruthenium complexes often showed good catalytic activity in transfer hydrogenation reactions, C–H bond functionalization (alkylation, arylation, sulfonylation, and allylation) and water oxidation reactions . Additionally, the good stability against water of half‐sandwich ruthenium complexes makes them ideal candidates to perform catalytic organic transformations in aqueous solution …”

Section: Introductionmentioning

confidence: 99%

Half‐sandwich ruthenium‐based versatile catalyst for both alcohol oxidation and catalytic hydrogenation of carbonyl compounds in aqueous media

Qiao

Qiu

Lin

et al. 2019

Applied Organom Chemis

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A series of half‐sandwich ruthenium‐based catalysts for both alcohol oxidation and carbonyl compounds hydrogenation have been synthesized through metal‐induced C–H bond activation based on benzothiazole ligands. The neutral ruthenium complexes 1–4 were fully characterized by UV–vis, NMR, IR, and elemental analysis. Molecular structures of complexes 1 and 3 were further confirmed by X‐ray diffraction analysis. All complexes exhibited high activity for the catalytic oxidation of a variety of alcohols with tBuOOH as oxidants to give carbonyl compounds with high yields in water. Moreover, these half‐sandwich complexes also showed high efficiency for the catalytic hydrogenation of carbonyl compounds in a methanol–water mixture. The catalyst could be reused for at least five cycles without any loss of activity. The catalytic system also worked well for various kinds of substrates with either electron‐donating or electron‐withdrawing groups.

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“…As for the understanding of the regioselectivity issue, detailed mechanistic study has been deficient in the literature until now, since current theoretical insights mainly rely on the use of NBO charge populations and Fukui function distributions[9c], [9d], rather than the location of transition states and estimation of kinetic parameters. In addition, the mechanism of the attack on the ruthenacycle has still been controversial.…”

Section: Introductionmentioning

confidence: 99%

Meta‐Selective C–H Alkylation of 2‐Phenylpyridine Catalyzed by Ruthenium: DFT Study on the Mechanism and Regioselectivity

Zhang

Zhou

et al. 2018

Eur J Org Chem

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Density functional theory calculations have been performed to quantitatively characterize ruthenium‐catalyzed meta‐selective C–H functionalizations of 2‐phenylpyridine. The reaction with tert‐butyl bromide was used as a model, and the proposed catalytic cycle is comprised of three successive steps: C–H activation, alkylation of the ruthenacycle, and demetalation, and separation of the product, among which C–H activation is the rate‐determining step having a free‐energy barrier of 29.2 kcal mol–1. Alkylation of the ruthenacycle is predicted to be the selectivity‐determining step. The plausible reaction mechanism of the alkylation of the ruthenacycle depends on the nature of alkylating reagents, because use of simple alkyl halides would favor the electrophilic aromatic substitution mechanism over the radical mechanism, while the radical mechanism might become more competitive if a tertiary α‐bromo ester serves as an alkylating source. To address the regioselectivity issue, the kinetic parameters for the formation of different regioisomeric products have been calculated, which are consistent with the experimental findings and can provide additional insights.

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Ruthenium-Catalyzed Remote C–H Sulfonylation of N-Aryl-2-aminopyridines with Aromatic Sulfonyl Chlorides

Cited by 44 publications

References 61 publications

Remote C–H Functionalizations by Ruthenium Catalysis

Remote C–H Functionalizations by Ruthenium Catalysis

Half‐sandwich ruthenium‐based versatile catalyst for both alcohol oxidation and catalytic hydrogenation of carbonyl compounds in aqueous media

Meta‐Selective C–H Alkylation of 2‐Phenylpyridine Catalyzed by Ruthenium: DFT Study on the Mechanism and Regioselectivity

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