Asymmetric synthesis of a chiral hetero-bidentate As–P ligand containing both As and P-stereogenic centres

The organopalladium complex containing ortho-metalated (S)-[1-(dimethylamino)ethyl]naphthalene as the chiral auxiliary has been used as the chiral template to promote the asymmetric cycloaddition reaction between phenyldivinylphosphine and 3,4-dimethyl-1-phenylarsole. The reaction was completed in 1 h at room temperature, with the formation of two isomeric cycloadducts in the ratio 1:3. The major phenylvinylphosphino-substituted asymmetrical hetero-bidentate arsanorbornene ligand with chirality residing on both As and P centers was obtained stereoselectively on the chiral palladium template in moderate yield. The chiral heterobidentate ligand was isolated in its enantiomerically pure form by removal of the chiral auxiliary using concentrated hydrochloric acid and subsequent cleavage from the neutral complex [(As–P)PdCl₂] by using potassium cyanide. Similar to the earlier reported analogous diphenylphosphino-substituted asymmetrical heterobidentate arsanorbornene (As–P) ligand, an arsenic elimination process was also found in the dichloro and dibromo palladium complex whereas the diiodo species did not show similar reactivity, but the corresponding η² diiodo complex could be obtained from the η² dibromo complex by treatment with sodium iodide.     

Magnetic iron oxide nanoparticles–N‐heterocyclic carbene–palladium(II): a new,efficient and robust recyclable catalyst for Mizoroki–Heck and Suzuki–Miyaura coupling reactions

A new and efficient nanoparticle–N‐heterocyclic carbene–palladium complex was synthesized and characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis, field emission scanning electron microscopy, energy‐dispersive X‐ray analysis, X‐ray diffraction, transmission electron microscopy, elemental analysis, inductively coupled plasma analysis and vibrating sample magnetometry. This catalytic system was found to be a highly active catalyst in the Mizoroki–Heck and Suzuki–Miyaura cross‐coupling reactions. These reactions were best performed in dimethylformamide and water, respectively, in the presence of only 0.054 mol% of palladium under mild conditions. Moreover, the catalyst could be recovered easily and reused at least ten times without any considerable loss of its catalytic activity. Copyright © 2016 John Wiley & Sons, Ltd.     

Pd(OAc)2@SBA‐15/PrEn nanoreactor: a highly active,reusable and selective phosphine‐free catalyst for Suzuki–Miyaura cross‐coupling reaction in aqueous media

A series of ordered mesoporous organic–inorganic hybrid material was designed by using the amine‐functionalized SBA‐15 (PdX₂@SBA‐15/N_Y, Y = 1, 2) as solid support for palladium complexes. Among them, the Pd(OAc)₂/ethylenediamine complex encapsulated into SBA‐15 (Pd(OAc)₂@SBA‐15/PrEn or Pd(OAc)₂@SBA‐15/PrNHEtNH₂) exhibits higher activity and selectivity toward Suzuki cross‐coupling reaction under aerobic conditions and water solvent mixture. The SBA‐15/PrEn supported palladium pre‐catalyst could be separated easily from reaction products and used repetitively several times, showing its superiority over homogeneous catalysts for industrial and chemical applications. Copyright © 2013 John Wiley & Sons, Ltd.     

Silica–acetylacetone‐supported palladium nanoparticles as an efficient and reusable catalyst in the Heck–Mizoroki C–C cross‐coupling reaction

The preparation of palladium nanoparticles supported on acetylacetone‐modified silica gel and their catalytic application for Heck olefination of aryl halides were investigated. The catalyst was characterized using X‐ray diffraction, X‐ray photoelectron spectroscopy, and transmission and scanning electron microscopies. The supported palladium nanoparticles are demonstrated to be a highly active and reusable catalyst for the Heck reaction. Several reaction parameters, including type and amount of solvent and base, were evaluated. The heterogeneity of the catalytic system was investigated with results indicating that there is a slight palladium leaching into the reaction solution under the applied reaction conditions. Despite this metal leaching, the catalyst can be reused nine times without significant loss of catalytic activity. Copyright © 2015 John Wiley & Sons, Ltd.     

Hydrogen electrosorption in Ni–Pd alloys

Hydrogen absorption in Ni–Pd alloys has been investigated. The amount of absorbed hydrogen in alloys containing below 20 at.% of nickel is equal to the amount of hydrogen sorbed in pure palladium. Hydrogen absorption occurs in the range 0–40 at.% of nickel concentration. Cyclic voltammograms recorded at Ni–Pd alloys have characteristic peaks which overlap with the responses due to processes occurring on the surface at Ni and Pd atoms. Also some of the processes characteristic of the pure metals can be distinguished from the recorded voltammograms.     

Palladium Membrane‐Installed Microchannel Devices for Instantaneous Suzuki–Miyaura Cross‐Coupling

Instantaneous catalytic carbon–carbon bond‐forming reactions were achieved in catalytic membrane‐installed microchannel devices that have a polymeric palladium‐complex membrane. The catalytic membrane‐installed microchannel devices were provided inside the microchannels by means of coordinative and ionic molecular convolution at the interface between the organic and aqueous phases flowing laminarly, in which both non‐crosslinked linear polymer ligands and palladium species dissolved. The palladium‐catalyzed Suzuki–Miyaura reaction of aryl, heteroaryl, and alkenyl halides with arylboronic acids and sodium tetraarylborates was performed with the catalytic membrane‐installed microchannel devices to give quantitative yields of biaryls, heterobiaryls, and aryl alkenes within 5 s of residence time in the defined channel region. These microchannel devices were applied to the instantaneous allylic arylation reaction of allylic esters with arylboron reagents under microflow conditions to afford the corresponding coupling products within 1 s of residence time.     

Synthesis of peroxide‐curable butyl rubber via suzuki–miyaura coupling of halogenated butyl rubber with 4‐vinylphenylboronic acid

The Suzuki–Miyaura coupling reaction of brominated butyl rubber (BIIR) and/or chlorinated butyl rubber with a mixture of 4‐vinylphenylboronic acid and phenylboronic acid was carried out in THF under various conditions using a di‐μ‐chlorobis [5‐hydroxy‐2‐[1‐(hydroxyimino‐κN)ethyl]phenylκC] palladium(II) dimer, which is a type of cyclopalladated complex, as a catalyst. When BIIR and a small amount (Pd/Br ≈ 1/1000) of complex were used as the substrate and catalyst, respectively, a 4‐vinylphenyl and phenyl group could be introduced to butyl rubber in a high yield. Isomerization of the exo carbon–carbon double bond in BIIR was observed during the coupling reaction to give a cis and trans endo structure. The peroxide curing behavior of the resulting polymer at 170 °C indicated that the polymer could be cured by dicumyl peroxide, and the maximum torque of the resulting material, which reflects the crosslink density, was controllable by the composition of the boronic acids used. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Silica‐supported terpyridine palladium(II) complex as an efficient and reusable catalyst for Heck and Suzuki cross‐coupling reactions

Silica‐supported terpyridine palladium(II) was prepared and used as an effective and recyclable catalyst in Mizoroki–Heck and Suzuki–Miyaura coupling reactions. The catalyst was very effective for the Mizoroki–Heck reaction of aryl halides with olefins and conversion was in most cases excellent. The catalyst showed good thermal stability (up to 230 °C) and could be recovered and reused for four reaction cycles. The Suzuki coupling of aryl iodides with aryl boronic acids in the presence of the catalyst was also investigated and the reaction proceeded with a short reaction time and excellent conversion. Copyright © 2013 John Wiley & Sons, Ltd.     

Salicylaldoxime‐functionalized poly(ethylene glycol)‐bridged dicationic ionic liquid ([salox‐PEG1000‐DIL][BF4]) as a novel ligand for palladium‐catalyzed Suzuki–Miyaura reaction in water

Two novel salicylaldoxime‐functionalized poly(ethylene glycol)‐bridged dicationic ionic liquids ([salox‐PEG₁₀₀₀‐DIL][BF₄] and [salox‐PEG₁₀₀₀‐DIL][PF₆]) were prepared and characterized. [salox‐PEG₁₀₀₀‐DIL][BF₄] was found to be an efficient and recyclable ligand for palladium‐catalyzed Suzuki–Miyaura reaction in water. The catalytic system could be easily recovered and reused for at least five runs only with slight decrease in its activity. Copyright © 2013 John Wiley & Sons, Ltd.     

An improved preparation of mesoporous silica‐supported Pd as sustainable catalysts for phosphine‐free Suzuki–Miyaura and Heck coupling reactions

An improved and eco‐friendly procedure has been developed to generate mesoporous silica‐supported palladium nanoparticles (SiO₂@PdNP) that could be used as a sustainable heterogeneous Pd catalyst for phosphine‐free Suzuki–Miyaura and Heck coupling reactions with excellent turnover number and turnover frequency. The presence of Pd on the silica surface was detected by X‐ray diffraction and the structural morphology of SiO₂@PdNP was obtained by transmission electron microscopy. The heterogeneous catalytic system is recyclable and leaching of the metal after the reaction is not apparently observed. Copyright © 2013 John Wiley & Sons, Ltd.     

A highly efficient heterogeneous montmorillonite K‐10‐supported palladium catalyst for Suzuki–Miyaura cross‐coupling reaction in aqueous medium

A heterogeneous montmorillonite K‐10‐supported palladium triphenylphosphine catalyst is reported for the Suzuki–Miyaura cross‐coupling reaction at room temperature. A library of electronically diverse aryl bromides and arylboronic acids underwent the cross‐coupling reaction at very good rates in aqueous solvent. The reusability of the catalyst was also examined and it was found to be effective up to three catalytic cycles. Copyright © 2014 John Wiley & Sons, Ltd.     

Cyclodextrin‐supported palladium complex: A highly active and recoverable catalyst for Suzuki–Miyaura cross‐coupling reaction in aqueous medium

A water‐soluble, cyclodextrin‐supported palladium complex (DACH‐Pd‐β‐CD) catalytic system was designed and synthesized, which can efficiently catalyze Suzuki–Miyaura cross‐coupling reactions between aryl halides and arylboronic acid in water under mild conditions. The catalyst was successfully characterized using the methods of transmission electron microscopy, energy‐dispersive X‐ray spectrometry, X‐ray diffraction, thermogravimetric analysis, and Fourier transform infrared and NMR spectroscopies. Furthermore, the catalyst can be easily separated from the reaction mixture and still maintain high catalytic activity after ten cycles. No leaching of palladium into the reaction solution occurred. The advantages of green solvent (water), short reaction times (2–6 h), low catalyst loading (0.001 mol%), excellent yields (up to 99%) and reusability of the catalyst mean it will have potential applications in green chemical synthesis.     

Metallomicelles of palladium(II) complexes as efficient catalysts for the Suzuki–Miyaura reaction in neat water

Metallomicelles of palladium(II) complex 4 are found to be an efficient catalyst for Suzuki–Miyaura reactions of aryl bromides substituted with a long alkyl chain and arylboronic acids at 80 °C in neat water. The reactions proceed smoothly to generate the corresponding biaryl compounds in moderate to excellent yields. Various biphenyl derivatives were successfully obtained by complex 4 catalysis of the Suzuki–Miyaura reactions in the absence of any surfactants in neat water. Copyright © 2013 John Wiley & Sons, Ltd.     

2‐Pyridylquinoxaline derivatives as N,N‐ligands for palladium‐catalyzed Suzuki–Miyaura reaction

The Suzuki–Miyaura reaction of aryl bromides with benzeneboronic acid catalyzed by bis(chloro)(2‐pyridylquinoxaline)palladium(II) was investigated. The scope of the bis(chloro)(2‐pyridylquinoxaline)palladium(II) was determined in toluene at 80 °C using KOH as base. Using a 0.1% molar ratio of bis(chloro)(2‐pyridylquinoxaline)palladium(II) C1 as a catalyst, aryl bromides reacted with benzeneboronic acid to afford diaryl derivatives in excellent yield. Copyright © 2009 John Wiley & Sons, Ltd.     

Preparation of siloxene nanosheet‐supported palladium as sustainable catalyst for Mizoroki–Heck reaction

Siloxene nanosheets were successfully modified with palladium nanoparticles by reducing palladium chloride with hydrazine hydrate. The palladium nanoparticles–siloxene nanosheets as a catalyst for the Mizoroki–Heck reaction exhibited high activity, recoverability and stability. The structural morphology of the catalyst was investigated using transmission electron microscopy. High efficiency of the catalyst was proved in the Mizoroki–Heck reaction after five catalytic recycles. Copyright © 2014 John Wiley & Sons, Ltd.     

Polyacrylonitrile fiber mat‐supported palladium catalyst for Mizoroki–Heck reaction in aqueous solution

A novel palladium catalyst immobilized on polyacrylonitrile fiber mats (Pd/PAN) was prepared by electrospinning. The catalytic activity and recyclability of the microwave‐assisted Pd/PAN fiber mats were examined for the Mizoroki–Heck cross‐coupling of aryl iodides with three different acrylates in aqueous solution. The morphology of the prepared Pd/PAN fiber mats was characterized by scanning electron microscopy. The large size of the PAN fiber mat‐supported palladium catalyst enables much easier separation from the reaction mixture by simple filtration. Density functional theory calculation indicates that the chelation energy of palladium chloride (PdCl₂) with propionitrile (model of PAN) is considerable smaller than that of PdCl₂ with water, suggesting that the stability and reactivity of the Pd/PAN fiber mats catalyst could be improved through the surface derivatization with polar functional groups. Copyright © 2011 John Wiley & Sons, Ltd.     

Aryl–Phenyl Scrambling in Intermediate Organopalladium Complexes: A Gas‐Phase Study of the Mizoroki–Heck Reaction

The intramolecular aryl–phenyl scrambling reaction within palladium–DPPP–aryl complex (DPPP=1,3‐bis(diphenylphosphino)propane) ions was analyzed by state‐of‐the‐art tandem MS, including gas‐phase ion/molecule reactions. The Mizoroki–Heck cross‐coupling reaction was performed in the gas phase, and the intrinsic reactivity of important intermediates could be examined. Moreover, linear free‐energy correlations were applied, and a mechanism for the scrambling reaction proceeding via phosphonium cations was assumed.     

Competitive hydrogenation in alkene–alkyne–diene systems with palladium and platinum catalysts

Competitive hydrogenation of alkene, alkyne and diene substrates (C₆–C₈) over palladium and platinum catalysts were studied at 20°C and atmospheric pressure. Selectivities of these reactions were determined and the substrates relative adsorption coefficients calculated. It was found that hydrogenations of alkynic and dienic substrates were preferred in alkyne–alkene and diene–alkene systems, respectively. In these systems palladium catalyst selectivity was higher than selectivity of the platinum catalyst, due to higher relative adsorption coefficients of corresponding substrate couples on the palladium catalyst.     

A highly water‐dispersible and magnetically separable palladium catalyst based on functionalized poly(ethylene glycol)‐supported iminophosphine for Suzuki–Miyaura coupling in water

A magnetically separable Fe₃O₄@poly(ethylene glycol) (PEG)–iminophosphine palladium complex was successfully prepared by reacting a palladium complex containing the ligand 2‐(diphenylphosphino)benzaldehyde with amino‐functionalized PEG‐coated iron oxide nanoparticles. The novel catalyst was characterized using inductively coupled plasma atomic emission and Fourier transform infrared spectroscopies, transmission electron microscopy, vibrating sample magnetometry, X‐ray diffraction and thermogravimetric analysis. It showed high activity for the Suzuki–Miyaura coupling reaction in pure water. Furthermore, it was found that the highly water‐dispersible catalyst can be recovered by applying an external magnetic field and used in five consecutive runs without significant decrease in activity. Copyright © 2015 John Wiley & Sons, Ltd.     

A phosphine‐free heterogeneous Suzuki–Miyaura reaction of aryl bromides catalyzed by MCM‐41‐supported tridentate nitrogen palladium complex under air

MCM‐41‐supported tridentate nitrogen palladium(II) complex [MCM‐41‐3 N‐Pd(II)] was conveniently synthesized from commercially available and cheap 3‐(2‐aminoethylamino)propyltrimethoxysilane via immobilization on MCM‐41, followed by reacting with pyridine‐2‐carboxaldehyde and PdCl₂. It was found that this palladium complex is an excellent catalyst for the Suzuki–Miyaura coupling reaction of aryl bromides on two points: (i) the use of 5 × 10⁻⁴ mol equiv. of MCM‐41‐3 N‐Pd(II) under air afforded the coupling products efficiently after easy workup; (2) the catalyst can be reused many times without loss of catalytic activity. Copyright © 2011 John Wiley & Sons, Ltd.