Equilibrium CH acidity of arylacetylenes in dimethyl sulfoxide

Terekhova, M. I.; Петров, Е. С.; Василевский, С. Ф.; Ivanov, V. F.; Shvartsberg, M. S.

doi:10.1007/bf00947852

Cited by 3 publications

(5 citation statements)

References 6 publications

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“…Nevertheless, these results show that the electronic effects of the substituent play a relatively minor role in the acidity of acetylenes. This conclusion is also consistent with the observation that ρ-parameter in the correlation of the potassium p K of arylacetylenes in DMSO vs. σ° is only 3.5, almost four times less than that for toluenes.…”

Section: Resultssupporting

confidence: 91%

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Lithium and Cesium Ion-Pair Acidities of Some Terminal Acetylenes and Aggregation in Tetrahydrofuran¹

Gareyev

Streitwieser

1996

J. Org. Chem.

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The equilibrium lithium acidities in THF have been determined for 4-ethynylbiphenyl, EB (pK 21.5-22.3), 3,3,3-triphenylpropyne, TPP (pK 22.3-22.7), and 1-ethynyladamantane, EA (pK 23.7). Ion pairs of (4-ethynylbiphenylyl)lithium are aggregated in the concentration range from 10(-)(4) to 10(-)(3) M, with an average aggregation number of 2.5. (3,3,3-Triphenylpropynyl)lithium ion pairs are partially aggregated at concentrations from 10(-)(5) to 10(-)(3) M; the average aggregation number is 1.2. Cesium acidities in THF have been determined for 3,3,3-triphenylpropyne (pK 29.1-29.9) and 1-ethynyladamantane (pK 31.56). The average aggregation number of (3,3,3-triphenylpropynyl)cesium ion pairs is 6.2 at concentrations of 10(-)(4)-10(-)(3) M.

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Section: Resultssupporting

confidence: 91%

“…Reported acidity values for some aryl- and alkylacetylenes differ by as much as 8 p K units, depending on the solvent and counterion. For example, p K values for phenylacetylene were reported to be 23.2 in cyclohexylamine with lithium cation, 28.7 and 29.1 in DMSO with potassium counterion, and 31.1 with [2.1.1]cryptated lithium in THF.…”

Section: Introductionmentioning

confidence: 99%

Lithium and Cesium Ion-Pair Acidities of Some Terminal Acetylenes and Aggregation in Tetrahydrofuran¹

Gareyev

Streitwieser

1996

J. Org. Chem.

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“…It is a common knowledge that rate of the Sonogashira coupling increases when passing from electron‐donating to electron‐withdrawing substituents. In other words, the higher CH‐acidity of alkynes‐1 (pK), the higher the reaction rate …”

Section: Resultsmentioning

confidence: 99%

“…It is known that more sterically hindered tri(1‐naphthyl)phosphine (Np 3 P) was found to be an excellent ligand for metal complex catalysts inducing many types of transformations (Heck, Suzuki, etc.) . However, the data on application of Np 3 P in the Sonogashira reaction are lacking in the literature.…”

Section: Introductionmentioning

confidence: 99%

Tri(1‐naphthyl)phosphine as a ligand in palladium‐free Sonogashira cross‐coupling of arylhalogenides with acetylenes

Govdi

Vasilevsky

Малышева

et al. 2018

Heteroatom Chemistry

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Tri(1‐naphthyl)phosphine (Np3P) has been easily prepared in 34% yield from red phosphorus and 1‐bromonaphthalene in the superbasic system t‐BuONa/DMSO. The expedient procedures for the synthesis of aryl acetylenes by Sonogashira coupling of aryl iodides with terminal alkynes using Np3P as a ligand have been developed. For the first time, it is found that the reaction with compounds containing electron‐donating substituents preferably affords buta‐1,3‐diynes.

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“…In 1975, Heck proposed a mechanism where the oxidative addition complex generates the σ-complex C by the direct reaction with the deprotonated acetylene . A simple comparison of the high p K a of the acetylene (the p K a of phenylacetylene is >20) with the bases generally used does not support this hypothesis . In 2003, Soheili and co-workers at Merck proposed a mechanism where the acetylene, entering the metal coordination sphere, generates the π complex G , which, after π/σ ( G / C ) switching promoted by the base, efficiently produces the coupling product (Figure b) .…”

Section: Introductionmentioning

confidence: 99%

New Mechanistic Insights into the Copper-Free Heck–Cassar–Sonogashira Cross-Coupling Reaction

Palladino,

Fantoni,

Ferrazzano

et al. 2023

ACS Catal.

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The copper-free Heck–Cassar–Sonogashira (HCS) reaction, known since 1975, nowadays represents one of the most powerful methods for C–C bond formation in organic synthesis with several industrial applications. Despite its great success, the mechanism is still under discussion, with several reported possible pathways. To clarify the copper-free HCS reaction mechanism, stoichiometric and catalytic reactions were carried out and monitored by 31P/1H NMR spectroscopy, HPLC, and GC chromatography. In particular, the investigation of the role of the base, mimicking the real catalytic conditions, highlighted the fact that secondary amines rapidly induce precatalyst reduction and decrease the energy barrier for the alkyne carbopalladation step. The results supported the mechanism via direct coordination of the terminal alkyne on the oxidative addition complex. Depending on the palladium counterion, and independent of the solvent, aromatic substitutions, temperature, and terminal alkyne substitution, these studies support two different pathways: with halides, a neutral route, and with the triflate, a cationic one.

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Equilibrium CH acidity of arylacetylenes in dimethyl sulfoxide

Cited by 3 publications

References 6 publications

Lithium and Cesium Ion-Pair Acidities of Some Terminal Acetylenes and Aggregation in Tetrahydrofuran¹

Lithium and Cesium Ion-Pair Acidities of Some Terminal Acetylenes and Aggregation in Tetrahydrofuran¹

Tri(1‐naphthyl)phosphine as a ligand in palladium‐free Sonogashira cross‐coupling of arylhalogenides with acetylenes

New Mechanistic Insights into the Copper-Free Heck–Cassar–Sonogashira Cross-Coupling Reaction

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Equilibrium CH acidity of arylacetylenes in dimethyl sulfoxide

Cited by 3 publications

References 6 publications

Lithium and Cesium Ion-Pair Acidities of Some Terminal Acetylenes and Aggregation in Tetrahydrofuran1

Lithium and Cesium Ion-Pair Acidities of Some Terminal Acetylenes and Aggregation in Tetrahydrofuran1

Tri(1‐naphthyl)phosphine as a ligand in palladium‐free Sonogashira cross‐coupling of arylhalogenides with acetylenes

New Mechanistic Insights into the Copper-Free Heck–Cassar–Sonogashira Cross-Coupling Reaction

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Product

Resources

About

Lithium and Cesium Ion-Pair Acidities of Some Terminal Acetylenes and Aggregation in Tetrahydrofuran¹

Lithium and Cesium Ion-Pair Acidities of Some Terminal Acetylenes and Aggregation in Tetrahydrofuran¹