Silica supported palladium-phosphine complex: recyclable catalyst for Suzuki-Miyaura cross-coupling reactions at ambient temperature

A new silica immobilized palladium-phosphine complex has been developed. It was found to be an efficient catalyst for Suzuki-Miyaura cross-coupling reactions under mild conditions. It is important to note that the supported catalyst could be reused at least 10 times without a significant loss of catalytic activity.     

Polyaniline supported palladium catalyzed Suzuki-Miyaura cross-coupling of bromo- and chloroarenes in water

Polyaniline supported palladium catalysts were prepared from different palladium precursors and all the catalysts are well characterized using ICP-AES, FTIR, TGA-DTA, SEM-EDX and XPS analysis. All the catalysts were tested for Suzuki-Miyaura coupling of bromo- and chloroarenes in water and the catalyst prepared from PdCl₂ precursor was found to be the most effective catalyst. The catalyst can easily be recovered by simple filtration and reused for several cycles with almost consistent activity.     

Beta-aminoethyltrifluoroborates: efficient aminoethylations via Suzuki-Miyaura cross-coupling

A set of phenethylamines has been successfully prepared via Suzuki-Miyaura cross-coupling of diverse potassium beta-aminoethyltrifluoroborates with aryl halides. The potassium beta-aminoethyltrifluoroborates were easily prepared via hydroboration of enamine and enamide precursors. [reaction: see text].     

Silica-coated magnetic palladium nanocatalyst for Suzuki-Miyaura cross-coupling

A silica-coated magnetically separable Schiff-base palladium nanocatalyst was developed. Amorphous silica was used to encapsulate the magnetic Fe₃O₄ and an organic amine functionality was added to the silica surface. The amino group was treated with 1, 10-phenanthroline-2,9-dicarboxaldehyde to produce a Schiff-base, which was then treated with palladium to produce the silica coated magnetic Schiff-base palladium nanocatalyst. The palladium nanocatalyst was fully characterized using several spectroscopic techniques. The HR-SEM image of silica coated Fe₃O₄ revealed a globular shape with a diameter of 145 nm, along with this the average palladium nanoparticle size was 3.5 ± 0.6 nm. The successful functionalization and the appearances of the palladium species as a magnetic catalyst was confirmed by FT-IR and XRD analysis. The palladium nanocatalyst was successfully applied for the construction of CC bonds via Suzuki-Miyaura reaction. With a variety of organoboronic acids, the catalyst displayed great performance for electron-poor and electron-rich aryl halides, resulting in excellent yields of the corresponding cross-coupling products. The magnetic catalyst was retrieved from the reaction vial using an external strong magnet, and it was reused seven times without a significant drop in the production of the corresponding biaryl product.     

Synthesis of 5-arylhistidines via a Suzuki-Miyaura cross-coupling

Microwave irradiation efficiently promoted the Suzuki-Miyaura reaction of a 5-bromohistidine with various arylboronic acids in the presence of a palladium catalyst. This methodology allowed the synthesis of histidines substituted at position 5 of the imidazole ring with a phenyl, a substituted phenyl, a pyridyl or a thienyl ring. The corresponding 5-arylhistidines were obtained in moderate to good yields.     

Ferrocenylimidazoline palladacycles: efficient phosphine-free catalysts for Suzuki-Miyaura cross-coupling reaction

A series of new ferrocenylimidazoline ligands 5 with different substituents in the imidazoline ring and their corresponding cyclopalladated complexes 6 were synthesized. Chloride-bridged palladacycle dimers 6, which are thermally stable and insensitive to air and moisture, have been evaluated as effective phosphine-free catalysts for the Suzuki reaction of aryl bromides with arylboronic acid. The catalyst 6b presents the highest efficiency in the coupling processes for less reactive 2-bromothiophene. Moreover, the reactions can be carried out at room temperature under aerobic conditions to give the corresponding biaryls in high yields. Additionally, the triphenylphosphine adduct of cyclopalladated ferrocenylimidazoline 7a was structurally characterized by single-crystal X-ray diffraction.     

Azidosubstituted arylboronic acids: synthesis and Suzuki-Miyaura cross-coupling reactions

Arylboronic acids having a remote azido group were prepared from the corresponding azidosubstituted aryl bromides via lithiation and treatment with trialkyl borates. Preparative yields were achieved when the starting aryl bromides possessed ortho-alkoxy groups, which would stabilize the intermediate aryllithium species. Conventional Suzuki cross-coupling of the arylboronic acids proceeded generally well with retention of azido group; however, sometimes azidomethyl fragment underwent oxidative transformation into a nitrile.     

Highly practical boronic acid surrogates for the Suzuki-Miyaura cross-coupling

Boronic acids and esters are well known substrates for the Suzuki-Miyaura cross-coupling. Yet their isolation can sometimes be tedious. We report here that the use of aryl dioxazaborocanes afford a simple isolation procedure while keeping a high efficiency in the cross-coupling process.     

Solid-phase synthesis of 5-arylhistidines via a microwave-assisted Suzuki-Miyaura cross-coupling

Microwave irradiation efficiently promoted the solid-phase Suzuki-Miyaura reaction of a 5-bromohistidine with various arylboronic acids in the presence of a palladium catalyst. This methodology allowed the synthesis of peptides bearing a histidine residue substituted at position 5 of the imidazole ring with a phenyl, a substituted phenyl, a pyridyl, or a thienyl ring, as well as with the benzene ring of a tyrosine residue.     

Efficient imidazolium salts for palladium-catalyzed Mizoroki-Heck and Suzuki-Miyaura cross-coupling reactions

The system, Pd(OAc)2/imidazolium salts (L2), was found as an efficient catalyst in the Heck coupling reaction of olefins with aryl halides and Suzuki reactions of various aryl halides with aryl boronic acids under aerobic condition. This catalytic system demonstrates great tolerance to a wide range of groups on all substrates of aryl halides, alkenes and aryl boronic acids.     

A polymer-supported salen-type palladium complex as a catalyst for the Suzuki-Miyaura cross-coupling reaction

A salen-type palladium(II) complex was readily immobilised onto a Merrifield resin. The supported complex is an effective recyclable heterogeneous catalyst for the Suzuki cross-coupling reaction without the use of phosphine ligands. Leaching of the metal into solution from the supported catalyst proved negligible.     

d-Glucosamine based-phosphine for Suzuki-Miyaura cross-coupling reactions in the supported aqueous phase catalysis system

A d-glucosamine-based phosphine/Pd(OAc)₂ complex has been applied to the Suzuki-Miyaura coupling reaction of aryl bromides with arylboronic acids using the supported aqueous phase catalysis, SAPC, concept. The recyclability of the catalyst was investigated and revealed a very high activity during the 4 runs.     

Preparation of polymer-supported phosphine from ferrocene for palladium-catalyzed Suzuki-Miyaura cross-coupling reactions

Polymer-supported phosphine ligand 3b derived from ferrocene was prepared,and applied in palladium-catalyzed Suzuki- Miyaura reactions.A range of aryl bromides can couple with phenylboronic acid to obtain corresponding biaryls in excellent yields. The recycling of the polymer-bound catalyst was tested without adding palladium.     

An active ferrocenyl triarylphosphine for palladium-catalyzed Suzuki-Miyaura cross-coupling of aryl halides

Pd-catalyzed Suzuki-Miyaura reaction of aryl chlorides was accomplished through the use of an active ferrocene-based triarylphosphine ligand. This air- and moisture-stable ligand was found to be effective for the cross-coupling of aryl halides at room temperature to 115 degrees C.     

Impregnated palladium on magnetite, a new catalyst for the ligand-free cross-coupling Suzuki-Miyaura reaction

A new catalyst for the cross-coupling Suzuki-Miyaura reaction is reported. The impregnated palladium on magnetite catalyst is very easy to prepare using the standard impregnation methodology. This catalyst avoids the use of any type of expensive and difficult handle organic ligand, showing excellent yields, under mild reaction conditions, for the classical formation of biaryl compounds. The catalyst is very easy to remove from the reaction medium, only by using a simple magnet, and it could be re-used up to three times with only a slightly decrease of the chemical yield.     

Convenient and efficient Suzuki-Miyaura cross-coupling catalyzed by a palladium/diazabutadiene system

[structure: see text]. A Pd(OAc)2/diazabutadiene system has been developed for the catalytic cross-coupling of aryl halides with arylboronic acids. A combination of the diazabutadiene DAB-Cy (1, N,N'-dicyclohexyl-1,4-dizabutadiene) and Pd(OAc)2 was found to form an excellent catalyst for the Suzuki-Miyaura cross-coupling of various aryl bromides and activated aryl chlorides with arylboronic acids.     

Click ionic liquids: a family of promising tunable solvents and application in Suzuki-Miyaura cross-coupling

A series of click ionic salts 4?a-4?n was prepared through click reaction of organic azides with alkyne-functionalized imidazolium or 2-methylimidazolium salts, followed by metathesis with lithium bis(trifluoromethanesulfonyl)amide or potassium hexafluorophosphate. All salts were characterized by IR, NMR, TGA, and DSC, and most of them can be classified as ionic liquids. Their steric and electronic properties can be easily tuned and modified through variation of the aromatic or aliphatic substituents at the imidazolium and/or triazolyl rings. The effect of anions and substituents at the two rings on the physicochemical properties was investigated. The charge and orbital distributions based on the optimized structures of cations in the salts were calculated. Reaction of 4?a with PdCl(2) produced mononuclear click complex 4?a-Pd, the structure of which was confirmed by single-crystal X-ray diffraction analysis. Suzuki-Miyaura cross-coupling shows good catalytic stability and high recyclability in the presence of PdCl(2) in 4?a. TEM and XPS analyses show formation of palladium nanoparticles after the reaction. The palladium NPs in 4?a are immobilized by the synergetic effect of coordination and electrostatic interactions with 1,2,3-triazolyl and imidazolium, respectively.