Bidentate phosphines as ligands in the palladium-catalyzed intramolecular arylation: the intermolecular base-assisted proton abstraction mechanism

Pascual, Sergio; Mendoza, Paula de; Braga, Ataualpa Albert Carmo; Maseras, Feliu; Echavarren, Antonio M.

doi:10.1016/j.tet.2008.01.056

Cited by 123 publications

(74 citation statements)

References 107 publications

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“…formation of 12, Scheme 3). In a further study 70 these workers showed that bidentate phosphines are excellent ligands for this process and concluded that at least in this case the reaction proceeds by an intermolecular base-assisted proton abstraction mechanism.…”

Section: Methodsmentioning

confidence: 96%

Mechanisms of C–H bond activation: rich synergy between computation and experiment

et al. 2009

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Image reproduced with permission of Christophe CoperetPapers published in this issue include:A combined picture from theory and experiments on water oxidation, oxygen reduction and proton pumping Per E. M. Siegbahn and Margareta R. A. Blomberg, Dalton Trans., 2009, DOI: 10.1039 Recent computational studies of C-H bond activation at late transition metal systems are discussed and processes where lone pair assistance via heteroatom co-ligands or carboxylates are highlighted as a particularly promising means of cleaving C-H bonds. The term 'ambiphilic metal ligand activation' (AMLA) is introduced to describe such reactions.

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Section: Methodsmentioning

confidence: 96%

Mechanisms of C–H bond activation: rich synergy between computation and experiment

et al. 2009

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“…26 To further support the proposed intermolecular carbonateassisted mechanism, Maseras, Echavarren, and co-workers used bidentate ligands, such as dppm, dppe, dppf, and Xantphos, in the development of a new set of conditions for the palladiumcatalyzed intramolecular direct arylation of aryl bromides. 27 Since it is unlikely that a carbonate could displace a bidentate phosphine ligand on the palladium, the intermolecular carbonate-assisted pathway is more likely to occur. .…”

Section: ¹1mentioning

confidence: 99%

“…Without this additive, very little conversion of starting material to product was obtained. The use of pivalic acid as an additive has allowed for the development of milder conditions and improved regioselectivity for many intramolecular direct arylation reactions, 26,27,48 as well as in the functionalization of electron-deficient arenes, 38c,38d,49,50 and electron-rich heteroarenes. 40,42,49a,5153 Computationally, the influence of the pivalate anion on the benzene CH bond cleaving transition state results in a decrease of 1.3 kcal mol ¹1 when compared to the bicarbonate anion (24.9 vs. 26.2 kcal mol ¹1 ).…”

Section: ç Additives Used To Enhance Reactivitymentioning

confidence: 99%

Overview of the Mechanistic Work on the Concerted Metallation–Deprotonation Pathway

2010

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The cleavage of aromatic CH bonds promoted by a metal and an intramolecular base has been described over 50 years ago. Herein, discussion of selected mechanistic studies of this transformation will be presented. The basic ligand on the metal was proven to play a pivotal role in the CH bond cleavage step and evidence of a single operative concerted metallation deprotonation mechanism unifies the different mechanistic studies.

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“…28,29 In addition, binepines are not particularly bulky, as shown above with their calculated buried volumes, and they commonly adopt ML 2 coordination modes in other catalytic reactions. 7 To get more insight on the nature of the active species formed with binepines in the current reaction, we studied the linearity of the ee of indane 3a vs the ee of ferrocenylbinepine 1i (Figure 1).…”

Section: ■ Mechanistic Considerationsmentioning

confidence: 96%

Efficient Pd⁰-Catalyzed Asymmetric Activation of Primary and Secondary C–H Bonds Enabled by Modular Binepine Ligands and Carbonate Bases

et al. 2015

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International audienceNew binepine ligands have been synthesized, and characterized and have been shown to induce high diastereo- and enantioselectivity in the intramolecular arylation of primary and secondary C(sp3)–H bonds, giving rise to fused cyclopentanes. The ligands were obtained as bench-stable phosphonium tetrafluoroborate salts that can be directly employed in catalysis. It was shown that a ferrocenyl P-substituent on the ligand allows achievement of high stereoselectivities in combination with potassium carbonate for the arylation of primary C–H bonds under unprecedentedly low temperature (90 °C) and catalyst loading (1–2 mol % Pd/2–3 mol % ligand). Using a base-free precatalyst, carbonate was shown to be the active base and to provide higher stereoselectivities than acetate and pivalate. The more difficult arylation of secondary C–H bonds could also be achieved and required fine-tuning of the ligand structure and the carbonate countercation. This method allowed generation of fused tricyclic products containing three adjacent stereocenters as single diastereoisomers and with moderate to high enantioselectivity. Experimental data indicated that the enantiodetermining C–H activation step involves a monoligated species. DFT (PBE0-D3) calculations were performed with a prototypical binepine ligand to understand the origin of the enantioselectivity. The preference for the major enantiomer was traced to the establishment of a more efficient network of weak attractive interactions between the phosphine ligand and the substrate

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Bidentate phosphines as ligands in the palladium-catalyzed intramolecular arylation: the intermolecular base-assisted proton abstraction mechanism

Cited by 123 publications

References 107 publications

Mechanisms of C–H bond activation: rich synergy between computation and experiment

Mechanisms of C–H bond activation: rich synergy between computation and experiment

Overview of the Mechanistic Work on the Concerted Metallation–Deprotonation Pathway

Efficient Pd⁰-Catalyzed Asymmetric Activation of Primary and Secondary C–H Bonds Enabled by Modular Binepine Ligands and Carbonate Bases

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Bidentate phosphines as ligands in the palladium-catalyzed intramolecular arylation: the intermolecular base-assisted proton abstraction mechanism

Cited by 123 publications

References 107 publications

Mechanisms of C–H bond activation: rich synergy between computation and experiment

Mechanisms of C–H bond activation: rich synergy between computation and experiment

Overview of the Mechanistic Work on the Concerted Metallation–Deprotonation Pathway

Efficient Pd0-Catalyzed Asymmetric Activation of Primary and Secondary C–H Bonds Enabled by Modular Binepine Ligands and Carbonate Bases

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Efficient Pd⁰-Catalyzed Asymmetric Activation of Primary and Secondary C–H Bonds Enabled by Modular Binepine Ligands and Carbonate Bases