Homocoupling Of Arylboronic Acids Research Articles

Amine‐bridged bis(phenol) ligands for efficient Pd‐catalyzed aqueous C‐C coupling reactions

The influence of ring size (5 or 6), chain length (1, 2 or 3) and bulkiness of N‐aryl substituents in amine‐bridged bis(phenol) ligands (1, 2, 3) on palladium‐catalyzed aqueous C‐C coupling reactions were revealed. The homocoupling of arylboronic acid can be completed in neat water with the aid of a catalytic amount of p‐toluenesulfonyl chloride (TsCl) in a very short time under anaerobic or aerobic conditions. Interestingly, the same catalytic system was efficient for Suzuki–Miyaura reaction in aqueous acetone under aerobic conditions in the absence of TsCl. The crystal structures of ligand 1 and three unsymmetrical fluorine‐substituted biaryl derivatives were also reported. Copyright © 2013 John Wiley & Sons, Ltd.

Fe3O4 nanoparticle-supported Cu(ii)-β-cyclodextrin complex as a magnetically recoverable and reusable catalyst for the synthesis of symmetrical biaryls and 1,2,3-triazoles from aryl boronic acids

We report here on the preparation of an efficient, easily recoverable and reusable Fe3O4 magnetic nanoparticle-supported Cu(II)-β-cyclodextrin complex catalyst for the synthesis of symmetrical biaryls and 1,2,3-triazoles from arylboronic acids. The presented Fe3O4 magnetic nanoparticle-supported Cu(II)-β-cyclodextrin complex catalyst was characterized by TEM, XRD, VSM, TGA, and FT-IR spectrometer. By using the catalyst, we have developed an efficient protocol for the homocoupling of aryl boronic acids for the synthesis of biaryls. The catalyst is also active in the synthesis of 1,2,3-triazoles via a one-pot reaction of an arylboronic acid with sodium azide in water followed by a click cyclization reaction with an alkyne at room temperature in air without any additives. The reusability of the prepared nanocatalyst was successfully examined four times with only a very slight loss of catalytic activity.

Highly stable PEGylated gold nanoparticles in water: applications in biology and catalysis

Here we report the synthesis of well dispersed gold nanoparticles (Au NPs), with diameters ranging between 5 and 60 nm, in water and demonstrate their potential usefulness in catalysis and biological applications. Functionalised polyethylene glycol-based thiol polymers (mPEG-SH) were used to stabilise the pre-synthesised NPs. Successful PEGylation of the NPs was confirmed by Dynamic Light Scattering (DLS) and zeta potential measurements. PEG coating of the NPs was found to be key to their colloidal stability in high ionic strength media, compared to bare citrate-stabilised NPs. Our results show that PEG–Au NPs with diameters <30 nm were useful as catalysts in the homocoupling of arylboronic acids in water. Additionally, PEG–Au NPs were also shown to be stable in biological fluids, non-cytotoxic to B16.F10 and CT-26 cell lines and able to successfully deliver siRNA to CT-26 cells, achieving a significant reduction (p < 0.05) in the expression levels of luciferase protein; making these NPs attractive for further biological studies.

Pd-Catalyzed Oxidative Homocoupling of Arylboronic Acids in Aqueous Ethanol at Room Temperature

The authors demonstrate for the first time that the Pd(OAc)2/N,O-ligands act as catalysts toward homocoupling of arylboronic acid in aqueous ethanol (95%) under mild conditions: at room temperature and under aerobic condition. Under the optimal reaction conditions, all reactions gave the homocoupling products in good to excellent yields.

ChemInform Abstract: Homocoupling of Arylboronic Acids Catalyzed by CuCl in Air at Room Temperature.

Homocoupling of arylboronic acids has been successfully carried out by using the inexpensive simple copper salt CuCl as the catalyst in methanol to obtain symmetric biaryls in good to excellent yields. The reaction proceeds with a CuCl loading of 2 mol-% under extremely mild conditions: in air, at room temperature, without the need of any additives such as base, oxidant, or ligand.

A fascinating Suzuki homo-coupling reaction over anchored gold Schiff base complexes on mesoporous host

We present a study of the use of chloro-functionalized mesoporous silicas as supports for immobilization of Au(III) Schiff base complex, and use of this composite material as heterogeneous catalyst for homocoupling of aryl boronic acid. The catalyst was characterised by XRD, FTIR, UV–vis DRS, TG-DTA, etc. Catalyst was initially tested using the coupling of phenylboronic acid with bromo benzene in the presence of K 2CO 3 and with xylene as solvent. The reaction was also tested in the absence of the aryl halide and K 2CO 3. The results indicate that in our catalytic system base is not needed for the activation of phenylboronic acid, and its only role is to neutralize the boric acid. The optimized catalysts are also active in the coupling of a range of aryl boronic acids, and after four catalytic runs they show virtually no drop in activity.

Abnormal N-Heterocyclic Carbene Promoted Suzuki−Miyaura Coupling Reaction: A Comparative Study

A C2-protected imidazolium salt that generates an abnormal N-heterocyclic carbene (NHC) was applied for the palladium-catalyzed Suzuki−Miyaura coupling reactions. The abnormal NHC precursor promoted the reactions while suppressing homocoupling of aryl boronic acid, which was observed with the corresponding normal NHC precursor. The related well-defined abnormal NHC-based palladium complexes also showed better activity than the normal NHC-based analogues, exhibiting faster reaction rates especially at the initial stage of the reaction.

ChemInform Abstract: Homocoupling of Arylboronic Acids and Potassium Aryltrifluoroborates Catalyzed by Protein‐Stabilized Palladium Nanoparticles under Air in Water.

AbstractThe palladium nanoparticles are stabilized primarily within the protein cavity of a highly thermostable Dps protein from the thermophilic bacterium Thermosynechoccus elongatus.

Homocoupling of arylboronic acids and potassium aryltrifluoroborates catalyzed by protein-stabilized palladium nanoparticles under air in water

Palladium nanoparticles stabilized primarily within the protein cavity of a highly thermostable Dps protein (DNA binding protein from starved cells) from the thermophilic bacterium Thermosynechoccus elongatus provide an efficient catalyst for the homocoupling of boronic acids and potassium aryltrifluoroborates in water under aerobic phosphine-free conditions. Symmetrical biaryls have been isolated in good to excellent yields. Potassium aryltrifluoroborates give similar or better results than the corresponding arylboronic acids.

Magnetically separable nanoferrite-anchored glutathione: aqueous homocoupling of arylboronic acids under microwave irradiation

A highly active, stable and magnetically separable glutathione-based organocatalyst provided very good to excellent yields to symmetric biaryls in the homocoupling of arylboronic acids under microwave irradiation.

Design of Redox-Mediatory Systems for Electro-Organic Synthesis

Halide ion-promoted desulfo-halogenation was applied successfully to synthesis of 4-chloro-2-azetidinone 1, a potent intermediate for carbapenem synthesis, and stereoselective N-glycosylation of 2,3-deoxyglycosides. Bromide ion/N-oxyl compounds (TEMPO) double mediatory systems enabled us to develop several aqueous electrolysis media free from organic solvents, e.g., silica gel or polymer particles/water disperse systems and water-soluble TEMPO-mediated oil-in-water emulsion systems, in which electrooxidation of alcohols was carried out successfully in a simple beaker-type undivided cell under a constant current condition. Notably, the work-up process was very simple and the solid particles (disperse phase) and the aqueous solutions (disperse media) were easily recovered and reused, offering a totally closed system. In Pd(OAc)2/TEMPO double mediatory systems, electrogeneration of active cationic palladium catalysts was integrated into electrooxidative Wacker-type reaction. In a similar manner, Wacker-type cyclization and homo-coupling of arylboronic acids were successfully achieved.

Homocoupling of Arylboronic Acids with a Catalyst System Consisting of a Palladium(II) N‐Heterocyclic Carbene Complex and p‐Benzoquinone.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Homocoupling of Arylboronic Acids with a Catalyst System Consisting of a Palladium(II) N-Heterocyclic Carbene Complex and p-Benzoquinone

In the presence of 1-3 mol% SIPr-ligated Pd(OAc) 2 and 0.6 equivalent of P-benzoquinone, various arylboronic acids underwent homocoupling in MeOH at ambient temperature to produce symmetrical biaryls in 38-96% yields.

Base- and Phosphine-Free Palladium-Catalyzed Homocoupling of ­Arylboronic Acid Derivatives under Air

In the presence of a catalytic amount of Pd(OAc) 2 , various arylboronic acids underwent homocoupling in MeOH at ambient temperature under air to give rise to symmetrical biaryls. The homocoupling of arylboronic acids was also carried out using polyurea-encapsulated Pd(OAc) 2 as a recyclable catalyst.

Tetrasubstituted Olefin Synthesis via Pd-Catalyzed Addition of Arylboronic Acids to Internal Alkynes Using O2 as an Oxidant

The Pd(II)-catalyzed reaction of arylboronic acids and internal alkynes provides a convenient route to a wide variety of tetrasubstituted olefins. The reaction is conducted in DMSO using molecular O2 as an oxidant in the absence of any base. The reaction involves the cis addition of two aryl groups from the arylboronic acid to opposite ends of the triple bond of the internal alkyne. The synthesis tolerates a wide variety of functional groups, including alcohol, aldehyde, ester, TMS, and acetal groups. Electron-rich dialkylacetylenes, such as 4-octyne, provide highly substituted 1,3-dienes in moderate yields. The very mild O2/DMSO conditions also afford good to excellent yields of biaryls by the homocoupling of arylboronic acids.

Palladium‐Catalyzed Homocoupling of Arylboronic Acids and Esters Using Fluoride in Aqueous Solvents.

AbstractFor Abstract see ChemInform Abstract in Full Text.

An Efficient High‐Yielding Approach for the Homocoupling of Aryl Boronic Acids.

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ChemInform Abstract: High Yields of Symmetrical Biaryls from Palladium‐Catalyzed Homocoupling of Arylboronic Acids Under Mild Conditions.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.