Faster palladium-catalyzed arylation of simple arenes in the presence of a methylketone: beneficial effect of an <i>a priori</i> interfering solvent in C–H activation

Salamanca, Vanesa; Albéniz, Ana C.

doi:10.1039/d1qo00236h

Cited by 19 publications

(16 citation statements)

References 68 publications

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“…The meta isomer is always the major one, especially in the case of pyridine. This regiochemistry in the C−H activation is the same observed in the non‐oxidative direct arylation reactions with the same ligand [38,39] . The presence of an ester ( 10 a ) or keto ( 11 a ) substituent in the arene does not provide a directing effect in this reaction that could shift the regioselectivity towards the ortho isomer.…”

Section: Resultssupporting

confidence: 61%

“…This value is lower than the one expected for a situation where the C−H activation is the only rate limiting step (KIE≈3.6), indicating that a preceding step, either the coordination of the arene or the actual reoxidation rate with O 2 , may also be influencing the overall reaction rate, with the C−H cleavage TS being nonetheless the highest in energy and therefore the most influential. This has been discussed before [39] …”

Section: Resultsmentioning

confidence: 89%

“…We report here the efficient oxidative Heck reaction with oxygen at atmospheric pressure as the sole oxidant of a number of fluoroarenes and other arenes with different substituents using the cooperating ligand [2, 2’‐bipyridin]‐6(1 H )‐one (bipy‐6‐OH). We have previously employed this ligand for the direct arylation of arenes and shown its role in assisting the C−H activation step [38,39] . Now, a set of reaction conditions have been developed for the oxidative Heck reaction that use minimum amount of additives (acids or bases) and can be applied to a variety of simple arenes.…”

Section: Introductionmentioning

confidence: 99%

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Non‐Chelate‐Assisted Palladium‐Catalyzed Aerobic Oxidative Heck Reaction of Fluorobenzenes and Other Arenes: When Does the C−H Activation Need Help?

Villalba

Albéniz

2021

Adv Synth Catal

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The pyridone fragment in the ligand [2, 2’‐bipyridin]‐6(1H)‐one (bipy‐6‐OH) enables the oxidative Heck reaction of simple arenes with oxygen as the sole oxidant and no redox mediator. Arenes with either electron‐donating or electron‐withdrawing groups can be functionalized in this way. Experimental data on the reaction with toluene as the model arene shows that the C−H activation step is turnover limiting and that the ligand structure is crucial to facilitate the reaction, which supports the involvement of the pyridone fragment in the C−H activation step. In the case of fluoroarenes, the alkenylation of mono and 1,2‐difluoro benzenes requires the presence of bipy‐6‐OH. In contrast, this ligand is detrimental for the alkenylation of 1,3‐difluoro, tri, tetra and pentafluoro benzenes which can be carried out using just [Pd(OAc)2]. This correlates with the acidity of the fluoroarenes, the most acidic undergoing easier C−H activation so other steps of the reaction such as the coordination‐insertion of the olefin become kinetically important for polyfluorinated arenes. The use of just a catalytic amount of sodium molybdate as a base proved to be optimal in all these reactions.

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Section: Resultssupporting

confidence: 61%

Section: Resultsmentioning

confidence: 89%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Non‐Chelate‐Assisted Palladium‐Catalyzed Aerobic Oxidative Heck Reaction of Fluorobenzenes and Other Arenes: When Does the C−H Activation Need Help?

Villalba

Albéniz

2021

Adv Synth Catal

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“…In recent years, alternative catalytic systems have been developed for the non‐directed palladium‐catalyzed C−H functionalization of arenes, [2] greatly broadening the substrate scope beyond those bearing DGs. In the particular case of Pd‐catalyzed C−H arylation reactions, in most of the cases, an excess of the arene is needed, hampering the applicability of these methodologies to substrates of increasing complexity [3a–i] . Arene‐limited, non‐directed Pd‐catalyzed C−H arylation reactions remain challenging, with only few examples reported [3j–m] .…”

Section: Introductionmentioning

confidence: 99%

S,O‐Ligand Promoted meta‐C−H Arylation of Anisole Derivatives via Palladium/Norbornene Catalysis

et al. 2022

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Reversing the conventional site-selectivity of CÀ H activation processes provides new retrosynthetic disconnections to otherwise unreactive bonds. Here, we report a new catalytic system based on palladium/ norbornene and an S,O-ligand for the meta-CÀ H arylation of aryl ethers that significantly outperforms previously reported systems. We demonstrate the unique ability of this system to employ alkoxyarene substrates bearing electron donating and withdrawing substituents. Additionally, ortho-substituted aryl ethers are well tolerated, overcoming the "ortho constraint", which is the necessity to have a meta-substituent on the alkoxyarene to achieve high reaction efficiency, by enlisting novel norbornene mediators. Remarkably, for the first time the monoarylation of alkoxyarenes is achieved efficiently enabling the subsequent introduction of a second, different aryl coupling partner to rapidly furnish unsymmetrical terphenyls. Further insight into the reaction mechanism was achieved by isolation and characterization of some Pd-complexesbefore and after meta CÀ H activation-prior to evaluation of their respective catalytic activities.

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“…Heating at temperatures ranging from 100 °C to 140 °C for several hours or days is generally required [ 65 ]. Interestingly, a recent report by Albéniz and co-workers demonstrated the beneficial and non-innocent role of alternative solvents such as pinacolone [ 66 ].…”

Section: Introductionmentioning

confidence: 99%

Direct Arylation in the Presence of Palladium Pincer Complexes

et al. 2021

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Direct arylation is an atom-economical alternative to more established procedures such as Stille, Suzuki or Negishi arylation reactions. In comparison with other palladium sources and ligands, the use of palladium pincer complexes as catalysts or pre-catalysts for direct arylation has resulted in improved efficiency, higher reaction yields, and advantageous reaction conditions. In addition to a revision of the literature concerning intra- and intermolecular direct arylation reactions performed in the presence of palladium pincer complexes, the role of these remarkably active catalysts will also be discussed.

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Faster palladium-catalyzed arylation of simple arenes in the presence of a methylketone: beneficial effect of an a priori interfering solvent in C–H activation

Abstract: The functionalization of simple arenes without coordinating directing groups is a challenge. Besides facing the task of cleaving the sluggish C-H bond, the process is hampered by the weak coordinating...

Cited by 19 publications

References 68 publications

Non‐Chelate‐Assisted Palladium‐Catalyzed Aerobic Oxidative Heck Reaction of Fluorobenzenes and Other Arenes: When Does the C−H Activation Need Help?

Non‐Chelate‐Assisted Palladium‐Catalyzed Aerobic Oxidative Heck Reaction of Fluorobenzenes and Other Arenes: When Does the C−H Activation Need Help?

S,O‐Ligand Promoted meta‐C−H Arylation of Anisole Derivatives via Palladium/Norbornene Catalysis

Direct Arylation in the Presence of Palladium Pincer Complexes

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