Mechanistic investigation of Rh(<scp>i</scp>)-catalyzed alkyne–isatin decarbonylative coupling

Deng, Jian; Wen, Xiuling; Li, Juan

doi:10.1039/c7qo00122c

Cited by 10 publications

(2 citation statements)

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“…In the first part of the text we consider the formation of a hydride species from [Ir(emim)(η 4 -COD)(PPh 3 )] + ( 1 ), where the PPh 3 is used instead of m tppts. To find the active form of the catalyst, the displacement of the COD ligand needs to be considered as well, as the catalytic activity of iridium complexes in alkene hydrogenation is well-known. , Also, because formate insertion ( 3 ) is endergonic, the hydrogenation of COD to cyclooctene is required to precede this process, as shown in Figure . For the reaction of COD + 2H 2 = cyclooctane, Δ G is −33.1 kcal mol –1 .…”

Section: Resultsmentioning

confidence: 99%

DFT Study on the Mechanism of Hydrogen Storage Based on the Formate-Bicarbonate Equilibrium Catalyzed by an Ir-NHC Complex: An Elusive Intramolecular C–H Activation

Fehér

Horváth²,

Joó

et al. 2018

Inorg. Chem.

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A novel iridium based, water-soluble phosphine-NHC (N-heterocyclic carbene) complex, Na[Ir( emim)(η-COD)( mtppts)] was previously developed in our research group. It was shown that it is a very effective catalyst for the reversible storage of hydrogen based on the formate-bicarbonate equilibrium. In this paper, we present a DFT investigation on the noninnocent behavior of the NHC ligand toward C-H activation of the N-ethyl side chain and its possible role in the hydrogen storage mechanism. After preliminary investigations, using both computations and NMR measurements, we conclude that the COD ligand leaves the precatalyst irreversibly and the C-H activation takes place on a monophosphine complex. Two main pathways are considered in which the active Ir(III) complexes are generated differently: One is the cyclometalation path involving the ethyl side chain, the other is the oxidative addition step of a water molecule which has a higher barrier but provide a more stable starting state. We find that though the latter, a catalytic cycle where a hydride is abstracted from formate and gets protonated by solvent molecules gives the lowest calculated energy barrier, +25.8 kcal mol. That is, avoiding further redox processes is preferred. There are other pathways involving thermodynamically accessible C-H activated iridacycles but those involve slightly higher overall activation barriers due to the required Ir(I)/Ir(III) transitions. The cycle which involves only iridacycle intermediates offer the lowest energy span (energy difference calculated between only the highest and lowest energy points inside the cycle), however. Together with the experimental results, this implies that C-H activation of the N-ethyl side chain happens off-cycle or the starting solvent addition step of the dominant pathway is blocked kinetically. We also discuss the hydrogen uptake reaction catalyzed by cyclometalated species where the reduction of CO is preferred over reversing the first main cycle.

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Section: Resultsmentioning

confidence: 99%

DFT Study on the Mechanism of Hydrogen Storage Based on the Formate-Bicarbonate Equilibrium Catalyzed by an Ir-NHC Complex: An Elusive Intramolecular C–H Activation

Fehér

Horváth²,

Joó

et al. 2018

Inorg. Chem.

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“…Additionally, the development of an enantioselective decarbonylative process, which would lead to new types of asymmetric transformations, is also highly desirable. Finally, recent trends have focused on the use of DFT calculations to understand the decarbonylative process, ,− especially for the decarbonylation and transmetalation sequence in cross-coupling. Elegant computational studies on esters, amides, ,, acyl fluorides, , and in situ anhydrides ,, have been reported.…”

Section: Discussionmentioning

confidence: 99%

Selective Decarbonylation via Transition-Metal-Catalyzed Carbon–Carbon Bond Cleavage

et al. 2020

Chem. Rev.

194

123

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Transition-metal-catalyzed decarbonylation via carbon−carbon bond cleavage is an essential synthetic methodology. Given the ubiquity of carbonyl compounds, the selective decarbonylative process offers a distinct synthetic strategy using carbonyl groups as "traceless handles". This reaction has been significantly developed in recent years in many respects, including catalytic system development, mechanistic understanding, substrate scope, and application in the synthesis of complex functional molecules. Therefore, this review aims to summarize the recent progress on transition-metal-catalyzed decarbonylative process, from the discovery of new transformations to the understanding of reaction mechanisms, to reveal the great achievements and potentials in this field. The contents of this review are categorized by the type of chemical bond cleavage in the decarbonylative process. The main challenges and opportunities of the decarbonylative process are also examined with the goal of expanding the application range of decarbonylation reactions.

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Theoretical Study of Rh ‐Catalysis

2021

Computational Methods in Organometallic Catalysis

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Mechanistic investigation of Rh(i)-catalyzed alkyne–isatin decarbonylative coupling

Abstract: Theoretical studies reveal the ligand role in the Rh(i)-catalyzed alkyne–isatin decarbonylative coupling and account for the origin of chemo- and region-selectivity.

Cited by 10 publications

References 87 publications

DFT Study on the Mechanism of Hydrogen Storage Based on the Formate-Bicarbonate Equilibrium Catalyzed by an Ir-NHC Complex: An Elusive Intramolecular C–H Activation

DFT Study on the Mechanism of Hydrogen Storage Based on the Formate-Bicarbonate Equilibrium Catalyzed by an Ir-NHC Complex: An Elusive Intramolecular C–H Activation

Selective Decarbonylation via Transition-Metal-Catalyzed Carbon–Carbon Bond Cleavage

Theoretical Study of Rh ‐Catalysis

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