ChemInform Abstract: Bite Angle Effects of Diphosphines in C—C and C—X Bond Forming Cross Coupling Reactions

Birkholz, Mandy‐Nicole; Freixa, Zoraida; Leeuwen, Piet W. N. M. van

doi:10.1002/chin.200929255

Cited by 12 publications

(14 citation statements)

References 1 publication

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“…This destabilizing effect due to the need to decrease the ligand-metal-ligand angle (the bite angle) can be avoided by bending the catalyst in advance, as, for example, in chelate complexes Pd[PH 2 (CH 2 ) n PH 2 ] where the bite angle can be controlled by varying the length of the carbon-chain (CH 2 ) n . It is well known that the reactivity of a catalytic complex depends on its bite angle [21,[60][61][62][63][64]. By studying oxidative addition of several bonds to this series of model catalysts with n ¼ 2-6, bite angles from 98 to 156 can be achieved, and a clear relationship was found between the ligand-metal-ligand angles and the activation barriers.…”

Section: The Effect Of Ligand Variationmentioning

confidence: 94%

d10-ML2 Complexes: Structure, Bonding, and Catalytic Activity

Wolters¹,

Bickelhaupt

2014

Structure and Bonding

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Our goal in this chapter is to show how one can obtain a better understanding of the decisive factors for the selectivity and efficiency of catalytically active metal complexes. This ongoing research project has been designated the 'Fragment-oriented Design of Catalysts' and aims at providing design principles for a more rational development of catalysts. To this end, we have performed a series of studies in which we systematically investigate the effect of a specific variation on the reactivity of the catalyst. Thus, we will summarize previous results on not only how the reaction barrier varies when different bonds are activated by palladium, different ligands are attached to palladium but also how different metal centers perform compared to palladium. In a final section, we present a case study on newly obtained results about the effect of adding substituents with different electronegativity to the phosphine ligands at the metal center. A red thread throughout the chapter, and our methodology in general, is the application of the activation strain model of chemical reactivity. This is a predictive model that provides a quantitative relationship between trends in barrier heights and variation of geometric and electronic properties of the reactants.

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Section: The Effect Of Ligand Variationmentioning

confidence: 94%

d10-ML2 Complexes: Structure, Bonding, and Catalytic Activity

Wolters¹,

Bickelhaupt

2014

Structure and Bonding

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“…Respectively, over 26% and 57% of intermediate benzo [d][1,3]dioxol-5-ylmethyl acetate (VII) were also present in the reaction mixture after 18 h. As previously reported in the literature, this may be a consequence of the different diphosphine bite angles [8,52]. It is in fact known that when catalysts bearing chelating diphosphine ligands are used, the natural bite angle of the ligand backbone may considerably modify the electronic and steric properties of the metal complex influencing its reactivity [51][52][53][54][55]. Data reported in Table 2 are perfectly in line with this hypothesis since the best-performing ligand (DPPF) has a wider bite angle (99.1 • ), giving a quantitative conversion of (V) both in the presence of DMC and IPAc (Entries 2, 4-6 and 8, Table 2).…”

Section: One-pot Methoxycarbonylation Of Piperonyl Alcohol (V)mentioning

confidence: 53%

Synthesis of 2-Alkylaryl and Furanyl Acetates by Palladium Catalysed Carbonylation of Alcohols

et al. 2022

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The one-pot alkoxycarbonylation of halo-free alkylaryl and furanyl alcohols represents a sustainable alternative for the synthesis of alkylaryl and furanyl acetates. In this paper, the reaction between benzyl alcohol, chosen as a model substrate, CH3OH and CO was tested in the presence of a homogeneous palladium catalyst, an activator (isopropenyl acetate (IPAc) or dimethyl carbonate (DMC)) and a base (Cs2CO3). The influence of various reaction parameters such as the CO pressure, ligand and palladium precursor employed, mmol% catalyst load, temperature and time were investigated. The results demonstrate that decreasing the CO pressure from 50 bar to 5 bar at 130 °C for 18 h increases yields in benzyl acetate from 36% to over 98%. Further experiments were performed in the presence of piperonyl and furfuryl alcohol, interesting substrates employed for the synthesis of various fine chemicals. Moreover, furfuryl alcohol is a lignocellulosic-derived building block employed for the synthesis of functionalized furans such as 2-alkylfurfuryl acetates. Both the alcohols were successfully transformed in the corresponding acetate (yields above 96%) in rather mild reaction conditions (5–0.01 mol% catalyst, 5–2 bar CO pressure, 130 °C, 4–18h), demonstrating that the alkoxycarbonylation of alcohols represents a promising sustainable alternative to more impactful industrial practices adopted to date for the synthesis of alkylaryl and furfuryl acetates.

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“…Despite the first cross-coupling of an unactivated C–O bond having been demonstrated in 1979, to date, only a handful of methods have been reported to suppress nonproductive β-H elimination (BHE) during the reductive elimination (RE) in alkylative cleavage of an unreactive C–O bond with β-H-containing nucleophiles in the absence of directing groups . Because polydentate ligands hold the potential to suppress nonproductive β-H elimination by occupying the vacant orbital of an alkyl-metal agostic complex, Shi and co-workers documented the nickel-catalyzed alkylative cross-coupling of the benzylic C–OMe bond with β-H-containing alkyl Grignard reagents by using bidentate dppf as the ligand . Moreover, nickel-catalyzed alkylative cross-couplings of anisole derivatives with alkyl Grignard reagents and trialkyl aluminum reagents were also revealed by the groups of Chatani and Rueping, and the bidentate phosphine ligand dcype with unique steric and electronic effects was found to suppress the β-H elimination efficiently .…”

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confidence: 95%

Enantioselective Alkylation of Unactivated C–O Bond: Solvent Molecule Affects Competing β-H Elimination and Reductive Elimination Dynamics

et al. 2023

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Despite the fact that metal-catalyzed asymmetric alkylative cross-couplings have been well-established, enantioselective alkylative substitution of an unactivated C–O bond remains a challenge due to the lack of strategies to cleave the C–O bond and suppress β-H elimination as well as control stereochemistry simultaneously. Herein, the enantioselective alkylative activation of an unactivated C–O bond with β-H-containing alkylating reagents was described using a chiral nickel catalyst, and versatile axially chiral biaryls bearing alkyl moieties with different chain lengths were delivered in good yields and with high ee. Control experiments demonstrated the significant role of the solvent tetrahydrofuran to facilitate this transformation. DFT calculations revealed that the coordination of THF to Mg(II) is pivotal for suppressing β-H elimination during reductive elimination, thus unlocking how the solvent molecule affects the competing β-H elimination and reductive elimination dynamics in transition-metal-catalyzed alkylative cross-coupling reactions.

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ChemInform Abstract: Bite Angle Effects of Diphosphines in C—C and C—X Bond Forming Cross Coupling Reactions

Cited by 12 publications

References 1 publication

d10-ML2 Complexes: Structure, Bonding, and Catalytic Activity

d10-ML2 Complexes: Structure, Bonding, and Catalytic Activity

Synthesis of 2-Alkylaryl and Furanyl Acetates by Palladium Catalysed Carbonylation of Alcohols

Enantioselective Alkylation of Unactivated C–O Bond: Solvent Molecule Affects Competing β-H Elimination and Reductive Elimination Dynamics

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