Role of the base and endogenous anions in “ligand-free” catalytic systems for the Suzuki–Miyaura reaction

UV spectroscopic studies combined with kinetic measurements for the Suzuki–Miyaura reaction catalyzed by “ligand-free” catalytic systems have demonstrated that the base is involved in the formation of the palladium complexes ensuring the occurrence of the transmetalation stage. It follows from UV monitoring data for the catalytic reaction involving aryl iodides that a considerable part of palladium during the process is in the form of Pd²⁺ acid complexes with endogenous anions and does not participate in the main catalytic cycle.     

Suzuki reaction with aryl bromides at room temperature in the presence of a simple “ligand-free” catalytic system

Possibility was examined of using the simplest catalytic system (palladium salt and NaOH) in ethanol or in a mixture of ethanol and water as a catalyst precursor in order to obtain high product yields in the Suzuki reaction with nonactivated aryl bromides at room temperature without an inert atmosphere or ligand additives.     

A novel hydrophobic fluorous ionic liquid for ligand-free Mizoroki–Heck reaction

Mizoroki–Heck reaction is carried out in a novel hydrophobic fluorous ionic liquid which was catalyzed by Pd-nanoparticles formed in situ from Pd(OAc)₂ used in the reaction. This reaction is operable under mild, aerobic, and ligand-free conditions in excellent yields. Aryl iodides, bromides as well as chlorides can be used showing its versatility. The key feature of the system is that catalyst along with ionic liquid can be reused at least five times with superior activity.     

Mono- and dinuclear N-heterocyclic carbene palladium complexes with diazine ligands and their catalytic activities toward the Mizoroki–Heck reaction

Mono- and dinuclear N-heterocyclic carbene palladium complexes with diazine ligands were synthesized and characterized through adjusting the stoichiometric ratio of the reactants. The catalytic properties of all complexes were further studied in the Mizoroki–Heck reaction. The results indicated that the dinuclear complexes induced some benefits in catalytic behavior.     

Study of liquid–solid catalytic reaction of epichlorohydrin with sodium butyrate in the presence of tetrabutylammonium bromide

The liquid–solid catalytic reaction of epichlorohydrin and sodium butyrate with tetrabutylammonium bromide as a phase transfer catalyst was studied in this paper. The shrinking core model was applied. The analysis of the reaction based on the kinetic model showed a reaction-controlled regime at temperatures varying from 90 to 100°C. The exterior diffusivity was removed between 300 and 400 rpm. The internal diffusivity was removed when the particle size was 2 × 10^–4 m. Reaction rate constants were calculated at different temperatures. The correlation was obtained when the proposed kinetic model was applied to all the experimental data for predictive evaluations and the activation energy was 37.01 kJ mol^–1.     

Bio-surfactant: a green and environmentally benign reaction medium for ligand-free Pd-catalyzed Mizoroki–Heck cross-coupling reaction in water

Transition Metal Chemistry - A simple and efficient protocol for the ligand-free Mizoroki–Heck coupling reaction of various aryl bromides with different olefins has been reported by using in...     

N,N′-Mono substituted acyclic thioureas: efficient ligands for the palladium catalyzed Heck reaction of deactivated aryl bromides

A series of N,N′-mono substituted acyclic thiourea ligands are found to be highly active phosphine-free catalysts for palladium catalyzed Heck reaction of aryl iodides and bromides with olefins. We have achieved high turnover numbers for aryl iodides with olefins (TONs up to 970,000 for the reaction of iodobenzene with styrene).     

The effect of framework functionality on the catalytic activation of supported Pd nanoparticles in the Mizoroki–Heck coupling reaction

Palladium nanoparticles (Pd-NPs) were supported on functional and nonfunctional Co-coordination polymers (Pd/CoBDCNH₂ and Pd/CoBDC). Advanced analytical techniques revealed that Pd-NPs are supported on the external surface of the polymer framework and the functionalized framework possesses effective influence to prevent Pd-NP aggregation. Supported Pd-NPs were effectively applied as heterogeneous recyclable catalysts in the Mizoroki–Heck C–C cross coupling reactions of iodobenzene and either aromatic or aliphatic terminal alkenes. Catalytic results exhibited that highly dispersed Pd-NPs with low loading (1%) on the functional polymer (Pd/CoBDCNH₂) are more effective than aggregated Pd-NPs with high loading (9%) on the nonfunctional polymer (Pd/CoBDC). Both catalysts can simultaneously provide high activity and selectivity to E-coupled products, high efficiency in low amounts, easy separation of heterogeneous catalyst and appropriate performance in the recycling reaction without addition of a reducing agent.     

Study on the “Tin-Ene” reaction of α-bromoacetophenone and metallic tin with aldehydes

β-hydroxy ketones were obtained in good yields by the “tin-ene” reactions of α-bromoacetophenone and metallic tin with aldehydes.     

Study on the reaction of C60 with DL-valine and cyclohexanone

Reaction of C60 with DL-valine and cyclohexanone in refluxing chlorobenzene under N2 yields three [60]fulleropyrrolidine derivatives (mono-, bis- and triadduct) which are characterized on the basis of spectroscopies and cyclic voltammetry. It is found that the ratio of the three products greatly depends on the reaction conditions.     

Mechanistic Study of Catalysis in the Mizoroki–Heck Reaction with Anhydrides of Aromatic Acids

A kinetic study of reaction of alkene arylation by anhydrides of aromatic acids (modified Mizoroki–Heck reaction) was carried out using differential selectivity as the main measured parameter. The results obtained under conditions of competition between a pair of alkenes or a pair of aromatic anhydrides point to the occurrence of the reaction via a homogeneous mechanism of catalysis analogously to a conventional variant of reaction with aryl halides as arylating reagents. The hypothesis that the active catalyst is homogeneous agrees with the results of kinetic studies of processes of catalyst formation and deactivation.     

Magnetically recyclable Pd/γ-AlOOH@Fe_3O_4 catalysts and their catalytic performance for the Heck coupling reaction

Novel magnetically recyclable Pd/γ-AlOOH@Fe3O4 catalysts were prepared using γ-AlOOH@Fe3O4 as a magnetic supporter and nano-Pd particles as the active catalytic component.The structure of the catalysts was characterized by X-ray diffraction(XRD),transmission electron microscopy(TEM),N2 adsorption-desorption,and a vibration sample magnetometer(VSM).The catalytic activity and recyclability for the Heck coupling reaction were investigated.Results showed that the magnetic γ-AlOOH@Fe3O4 possessed a core-shell structure,as well as that the nano-Pd particles were 6–8 nm and had been well dispersed in the γ-AlOOH shell.In the Heck coupling reactions,the magnetic Pd/γ-AlOOH@Fe3O4 catalysts exhibited good catalytic activity and recyclability.For the(0.021 mol%)Pd/γ-AlOOH@Fe3O4 catalyst,the bromobenzene conversion and product yield reached about 100%and 96.3%,respectively,under a 120°C reaction temperature and 12 h reaction time.After being recycled 8 times,the conversion of bromobenzene and the recovery of the catalyst were about 90%and 93%,respectively.The nano-Pd particles were kept well dispersed in the used Pd/γ-AlOOH@Fe3O4 catalyst.     

A study of the color reaction of iron with “TTA”

Summary TTA, or 2-Thenoyltrifluoroacetone, gives with ferric ion, in various concentrations colorations ranging from blood red to light pink. The advantages of this test are that it is simple to perform, that it is applicable in different acid media of fairly high concentrations, and that it is somewhat sensitive in the presence of ions that usually interfere with such tests. The sensitivity (limit of identification) was found to be 0,5 and the limit of concentration 1 : 100000 when a benzene solution of the reagent was reacted with a slightly acid solution of ferric ion on spot paper.

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Zusammenfassung TTA (2-Thenoyltrifluoraceton) gibt mit Ferriionen je nach Konzentration der letzteren eine blutrote bis blaßrosa Färbung. Die Probe ist einfach ausführbar und wird durch die Gegenwart von Säuren bis zu ziemlich hohen Konzentrationen sowie durch die Gegenwart störender Ionen wenig beeinträchtigt. Wenn eine Lösung des Reagens in Benzol zu einer leicht angesäuerten Ferrisalzlösung zugesetzt wird, beträgt die Erfassungsgrenze 0,5 bei einer Grenzkonzentration von 1 : 100000.

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Résumé Le TTA, thénoyl-2 trifluoracétone, donne avec les ions ferriques, suivant leur concentration, une coloration rouge sang à rose pâle. L'essai est simple à effectuer et à peine troublé par la présence des acides jusqu'à des concentrations passablement élevées et par la présence des ions gênants. Quand on ajoute une solution du réactif dans le benzène à une solution peu acide de sel ferrique, on observe une limite de sensibilité de 0,5 pour une limite de dilution de 1 : 100000.

     

Gel-entrapped bases: A smart window for the ligand-free Suzuki–Miyaura cross-coupling reaction

A gel-entrapped base has been fabricated by using agarose (biopolymer), and tested in the Suzuki–Miyaura cross-coupling reaction in 95% ethanol. The developed environmentally benign polymer-supported base has low leaching and high stability for the Suzuki–Miyaura cross-coupling reaction to give high yield with green credit.     

Fabrication of magnetically separable palladium–graphene nanocomposite with unique catalytic property of hydrogenation

One step solvothermal route has been developed to prepare a well dispersed magnetically separable palladium–graphene nanocomposite, which can act as a unique catalyst against hydrogenation due to the uniform decoration of palladium nanoparticles throughout the surface of the magnetite–graphene nanocomposite and hence can be reused for several times. In addition to catalytic activity, palladium nanoparticles also facilitate the formation and homogeneous distribution of magnetite (Fe₃O₄) nanoparticles onto the graphene surfaces or else an agglomerated product has been obtained after the solvothermal reduction of graphene oxide in presence of Fe³⁺ alone.     

Catalase-like catalytic reaction of the dinuclear manganese–salen complex

Catalase-like activity of a dinuclear manganese-salen (Mn–salen) complex, [Mn(salen)(H₂O)]₂(ClO₄)₂ (salen = N,N ′-bis(salicylidene)-1,2-diaminoethane), was investigated. The dinuclear Mn–salen complex exhibits higher catalase-like activity than that of the mononuclear Mn–salen compound, and its activity can be enhanced by an external base. Different reaction intermediates in the presence and absence of an external base were observed, and the catalytically active species was dimeric as evidenced by UV-Vis spectroscopic studies and mass spectrometry data.     

Brønsted guanidine acid-base ionic liquids: novel reaction media for the palladium-catalyzed Heck reaction

[reaction: see text]. Br?nsted acid-base ionic liquids (GILs) based on guanidine and acetic acid are efficient reaction media for palladium-catalyzed Heck reactions. They offer the advantages of high activity and reusability. GIL2 plays multiple roles in the reaction: it could act as solvent, as a strong base to facilitate beta-hydride elimination, and as a ligand to stabilize activated Pd species.     

Synthesis of dienes with tetrafluorophenylene bridge based on the catalytic olefination reaction. New promising monomers for the design of molecular architectures with halogen—halogen interactions

Catalytic olefination of tetrafluoroterephthalic aldehyde hydrazone was studied. Dienes with a tetrafluorophenylene bridge containing different substituents at the double bonds were obtained. Stereochemistry of the reaction, as well as molecular structure and crystal packing of the dienes were studied.     

Nanosized Pd assembled on superparamagnetic core–shell microspheres:Synthesis,characterization and recyclable catalytic properties for the Heck reaction

A series of magnetically recyclable Pd/Fe3O4@g-Al2O3 catalysts were synthesized using the superparamagnetic Fe3O4@g-Al2O3core–shell microspheres as the supporter and nano-Pd particles assembled on g-Al2O3 shell as the active catalytic component.The structure of the catalysts was characterized by X-ray diffraction(XRD),transmission electron microscopy(TEM),N2adsorption–desorption and vibrating sample magnetometer(VSM).The catalytic activity and the recyclability properties of the catalysts for the Heck coupling reaction with aryl bromides and the olefins were investigated.The results show that the microspheres of the magnetic Pd/Fe3O4@g-Al2O3 catalysts were about 400 nm and the nano-Pd particles assembled on g-Al2O3 shell were about 3–4 nm in size.The saturation magnetization(MS) of the magnetic catalysts was sufficiently high to allow magnetic separations.In the Heck coupling reactions,the magnetic Pd/Fe3O4@g-Al2O3 catalysts exhibited good catalytic activity and recyclability.With Pd/Fe3O4@g-Al2O3(0.021 mol%) catalyst,the bromobenzene conversion and product yield reached about 96.8% and 91.2%,respectively,at 120 8C and in 14 h.After being recycled for six times,the conversion of bromobenzene and the recovery of the catalyst were about80% and 90%,respectively.The nano-Pd particles were kept well dispersed in the used Pd/Fe3O4@g-Al2O3 catalysts.     

Immobilization of palladium nanoparticles as a recyclable heterogeneous catalyst for the Suzuki–Miyaura coupling reaction

This work describes the synthesis of Pd nanoparticles that are stabilized on CaAl-layered double hydroxide functionalized with Tris (tris(hydroxymethyl)aminomethane). The synthesized catalyst is characterized by several different analyses and has been successfully applied to the Suzuki–Miyaura reaction.