First report of the direct supporting of palladium–arginine complex on boehmite nanoparticles and application in the synthesis of 5‐substituted tetrazoles

Boehmite nanoparticles are aluminium oxide hydroxide (γ‐AlOOH) particles, which were prepared using a simple and inexpensive procedure in water at room temperature and further modified using arginine. Subsequently palladium particles were immobilized on their surface to prepare Pd‐Arg@boehmite. This novel nanostructured compound was fully characterized using thermogravimetric analysis, X‐ray diffraction, inductively coupled plasma optical emission (ICP‐OES) and energy‐dispersive X‐ray spectroscopies, and scanning and transmission electron microscopies. Finally, this catalyst was applied as a moisture‐ and air‐stable heterogeneous material for the synthesis of 5‐substituted 1H –tetrazole derivatives. The leaching of palladium and heterogeneity of the catalyst were studied using hot filtration and ICP‐OES. This catalyst demonstrated remarkable recyclability. The novelty of this work is that it represents the first time an amino acid has been grafted on boehmite nanoparticles.     

Easy conversion of nitrogen‐rich silk cocoon biomass to magnetic nitrogen‐doped carbon nanomaterial for supporting of Palladium and its application

In this study, magnetic nitrogen‐doped carbon (MNC) was fabricated through facile carbonization and activation of natural silk cocoons containing nitrogen and then combined with Fe₃O₄ nanoparticles to create a good support material for palladium. Palladium immobilization on the support resulted in the formation of magnetic nitrogen‐doped carbon‐Pd (MNC‐Pd). The prepared heterogeneous catalyst was well characterized using FT‐IR, TGA, EDX, FE‐SEM, XRD, VSM, and ICP‐OES techniques. Thereafter, the synthesis of biaryl compounds was conducted to investigate the catalyst performance via the reaction of aryl halides and phenylboronic acid. Further, the catalyst could be used and recycled for six consecutive runs without any significant loss in its activity.     

Immobilized palladium nanoparticles on MNPs@A‐N‐AEB as an efficient catalyst for C‐O bond formation in water as a green Solvent

Palladium nanoparticles immobilized on the magnetic nanoparticles@2‐amino‐N‐(2‐aminoethyl) benzamide (MNPs@A‐N‐AEB.Pd⁰) have been presented as an efficient, and reusable magnetically heterogeneous catalyst for the C‐O coupling reaction, namely Ullmann condensation reactions in an aqueous medium. This heterogeneous catalyst shows superior reactivity for the C‐O arylation of different aryl halide (chloride, bromide, and iodide) with phenol derivatives to afford the desired products in good to excellent yields within short reaction time. Moreover, the catalyst can be easily recovered and reused for seven runs without loss of catalytic activity. The catalyst was characterized by several techniques, such as FT‐IR, SEM, TEM, EDS, XRD, TGA and ICP‐OES.     

Pd(0)‐ S‐propyl‐2‐aminobenzothioate immobilized onto functionalized magnetic nanoporous MCM‐41 as efficient and recyclable nanocatalyst for the Suzuki,Stille and Heck cross coupling reactions

The present work describes the use of Pd(0)‐ S‐propyl‐2‐aminobenzothioate Complex immobilized onto functionalized magnetic nanoporous MCM‐41(Fe₃O₄@MCM‐41@Pd‐SPATB) as efficient and recyclable nano‐organometallic catalyst for C–C bond formation between various aryl halides with phenylboronic acid (Suzuki reaction), aryl halides with triphenyltin chloride (Stille reaction), and aryl halides with n‐butyl acrylate (Heck reaction). All the reactions were carried out in PEG‐400 as green solvent with short reaction time and good to excellent yields. This catalyst was characterized by FT‐IR spectroscopy, XRD, TGA, VSM, ICP‐OES, TEM, EDX and SEM techniques. Ease of operation, high efficiency, recovery and reusability for five continuous cycles without significant loss of its catalytic activities or metal leaching are the noteworthy features of the currently employed heterogeneous catalytic system.     

Efficient synthesis of 5‐substituted tetrazoles catalysed by palladium–S‐methylisothiourea complex supported on boehmite nanoparticles

An efficient and general method is reported for the synthesis of 5‐substituted 1H ‐tetrazole derivatives in the presence of S ‐methylisothiourea complex of palladium immobilized on boehmite nanoparticles (Pd‐SMTU@boehmite) as an efficient and recyclable nanocatalyst. Boehmite nanoparticles were not sensitive to air or moisture and were prepared without inert atmosphere in water at room temperature. Then a novel type of phosphine‐free palladium complex was immobilized on these nanoparticles. This catalyst was characterized using Fourier transform infrared, thermogravimetric, Brunauer–Emmett–Teller, transmission and scanning electron microscopic, energy‐dispersive X‐ray spectroscopic, X‐ray diffraction and inductively coupled plasma optical emission spectroscopic techniques. The catalyst was reused several times without palladium leaching or change in its structure.     

Preparation and Characterization of Ni‐Modified Graphene Oxide Complex as an Efficient Catalyst for the Synthesis of Sulfides via Reaction of Arylhalides with S8 or Thiourea

In this work, complex of Ni‐modified graphene oxide was prepared and characterized using FT‐IR spectroscopy, SEM, XRD, TGA and ICP‐OES techniques. This compound used as an efficient and recoverable catalyst for the C–S coupling reaction using sulfur‐transfer reagents (S₈ or thiourea). The catalyst was easily separated using a simple filtration and reusable without significant loss of their catalytic efficiency.     

Magnetite tethered mesoionic carbene‐palladium (II): An efficient and reusable nanomagnetic catalyst for Suzuki‐Miyaura and Mizoroki‐Heck cross‐coupling reactions in aqueous medium

In this paper, a highly active, air‐ and moisture‐stable and easily recoverable magnetic nanoparticles tethered mesoionic carbene palladium (II) complex (MNPs‐MIC‐Pd) as nanomagnetic catalyst was successfully synthesized by a simplistic multistep synthesis under aerobic conditions using commercially available inexpensive chemicals for the first time. The synthesized MNPs‐MIC‐Pd nanomagnetic catalyst was in‐depth characterized by numerous physicochemical techniques such as FT‐IR, ICP‐AES, FESEM, EDS, TEM, p‐XRD, XPS, TGA and BET surface area analysis. The prepared MNPs‐MIC‐Pd nanomagnetic catalyst was used to catalyze the Suzuki–Miyaura and Mizoroki–Heck cross‐coupling reactions and exhibited excellent catalytic activity for various substrates under mild reaction conditions. Moreover, MNPs‐MIC‐Pd nanomagnetic catalyst could be easily and rapidly recovered by applying an external magnet. The recovered MNPs‐MIC‐Pd nanomagnetic catalyst exhibited very good catalytic activity up to ten times in Suzuki–Miyaura and five times in Mizoroki–Heck cross‐coupling reactions without considerable loss of its catalytic activity. However, MNPs‐MIC‐Pd nanomagnetic catalyst shows notable advantages such as heterogeneous nature, efficient catalytic activity, mild reaction conditions, easy magnetic work up and recyclability.     

Synthesis,characterization and catalytic performance of core‐shell structure magnetic Fe3O4/P(GMA‐EGDMA)‐NH2/HPG‐COOH‐Pd catalyst

A strategy has been developed for the synthesis, characterization and catalysis of magnetic Fe₃O₄/P(GMA‐EGDMA)‐NH₂/HPG‐COOH‐Pd core‐shell structure supported catalyst. The P(GMA‐EGDMA) polymer layer was coated on the surface of hollow magnetic Fe₃O₄ microspheres through the effect of KH570. The core‐shell magnetic Fe₃O₄/P(GMA‐EGDMA) modified by ‐NH₂ could be grafted with HPG. Then, the hyperbranched glycidyl (HPG) with terminal ‐OH were modified by ‐COOH and adsorbed Pd nanoparticles. The hyperbranched polymer layer not only protected the Fe₃O₄ magnetic core from acid–base substrate corrosion, but also provided a number of functional groups as binding sites for Pd nanoparticles. The prepared catalyst was characterized by UV–vis, TEM, SEM, FTIR, TGA, ICP‐OES, BET, XRD, DLS and VSM. The catalytic tests showed that the magnetic Fe₃O₄/P(GMA‐EGDMA)‐NH₂/HPG‐COOH‐Pd catalyst had excellent catalytic performance and retained 86% catalytic efficiency after 8 consecutive cycles.     

Heck and oxidative boron Heck reactions employing Pd(II) supported amphiphilized polyethyleneimine‐functionalized MCM‐41 (MCM‐41@aPEI‐Pd) as an efficient and recyclable nanocatalyst

A novel nanocatalyst was developed based on covalent surface functionalization of MCM‐41 with polyethyleneimine (PEI) using [3‐(2,3‐Epoxypropoxy)propyl] trimethoxysilane (EPO) as a cross‐linker. Amine functional groups on the surface of MCM‐41 were then conjugated with iodododecane to render an amphiphilic property to the catalyst. Palladium (II) was finally immobilized onto the MCM‐41@PEI‐dodecane and the resulted MCM‐41@aPEI‐Pd nanocatalyst was characterized by FT‐IR, TEM, ICP‐AES and XPS. Our designed nanocatalyst with a distinguished core‐shell structure and Pd²⁺ ions as catalytic centers was explored as an efficient and recyclable catalyst for Heck and oxidative boron Heck coupling reactions. In Heck coupling reaction, the catalytic activity of MCM‐41@aPEI‐Pd in the presence of triethylamine as base led to very high yields and selectivity. Meanwhile, the MCM‐41@aPEI‐Pd as the first semi‐heterogeneous palladium catalyst was examined in the C‐4 regioselective arylation of coumarin via the direct C‐H activation and the moderate to excellent yields were obtained toward different functional groups. Leaching test indicated the high stability of palladium on the surface of MCM‐41@aPEI‐Pd as it could be recycled for several runs without significant loss of its catalytic activity.     

N‐Heterocyclic carbene/phosphite synergistically assisted Pd/C‐catalyzed Suzuki coupling of aryl chlorides

An N‐heterocyclic carbene and phosphite synergistically enhanced Pd/C catalyst system has been developed for Suzuki coupling of aryl chlorides and aryl boronic acids from commercially available Pd/C with sterically demanding N,N′‐bis(2,6‐diisopropylphenyl)imidazolylidene and trimethylphosphite. A remarkable increase in catalytic activity of Pd/C was observed when used along with 1 equiv. N,N′‐bis(2,6‐diisopropylphenyl)imidazolium chloride and 2 equiv. phosphite with respect to palladium in appropriate solvents that were found to play a crucial role in Pd/C‐NHC‐P(OR)₃‐catalyzed Suzuki coupling. A dramatic ortho‐substitution effect of carbonyl and nitrile groups in aryl chlorides was observed and explained by a modified quasi‐heterogeneous catalysis mechanism. The Pd/C catalyst could be easily recovered from reaction mixtures by simple filtration and only low palladium contamination was detected in the biparyl products. A practical process for the synthesis of 4‐biphenylcarbonitrile has therefore been developed using the N‐heterocyclic carbene/phosphite‐assisted Pd/C‐catalyzed Suzuki coupling. Copyright © 2013 John Wiley & Sons, Ltd.     

Guanidine‐Functionalized Resin‐Supported Pd(0) Catalyst: Activity,Reusability, and Redeposition of Active Pd Species in Heck Vinylation

The guanidine‐functionalized resin‐supported Pd(0) catalyst [GDR·Pd(0)] is highly active in Heck reaction of aryl bromides with acrylic acid or styrene without the need to exclude air. The catalyst can be recycled at least 9 times without significant loss of activity in N‐methyl‐2‐pyrrolidone at 140 °C. The Heck reaction proceeds homogeneously with dissolved palladium species and the dissolved active palladium species can redeposit onto the surface of catalyst in the reaction. The XRD peak shifting of Pd phases in the catalyst provides the evidence for the re‐deposition of the active palladium species.     

Synthesis of multifunctional polymer containing Ni‐Pd NPs via thiol‐ene reaction for one‐pot cascade reactions

Recently, acid–base bifunctional catalysts have been considered due to their abilities, such as the simultaneous activation of electrophilic and nucleophilic species and their high importance in organic syntheses. However, the synthesis of acid–base catalysts is problematic due to the neutralization of acidic and basic groups. This work reports a facial approach to solve this problem via the synthesis of a novel bifunctional polymer using inexpensive materials and easy methods. In this way, at the first step, heterogeneous poly (styrene sulfonic acid‐n‐vinylimidazole) containing pentaerythritol tetra‐(3‐mercaptopropionate) (PETMP) and trimethylolpropane trimethacrylate (TMPTMA) cross‐linkers were synthesized in the pores of a mesoporous silica structure using click reaction as a novel bifunctional acid–base catalyst. After that, Ni‐Pd nanoparticles supported on poly (styrenesulfonic acid‐n‐vinylimidazole)/KIT‐6 as a novel trifunctional heterogeneous acid–base‐metal catalyst was prepared. The prepared catalysts were characterized by various techniques like FT‐IR, TGA, ICP‐AES, DRS‐UV, TEM, FE‐SEM, EDS‐Mapping, and XRD. The synthesized catalysts were efficiently used as bifunctional/trifunctional catalysts for one‐pot, deacetalization‐Knoevenagel condensation and one‐pot, three‐step and a sequential reaction containing deacetalization‐Knoevenagel condensation‐reduction reaction. It is important to note that the synthesized catalyst showing high chemo‐selectivity for the reduction of nitro group, alkenyl double bond and ester group in the presence of nitrile. Moreover, it was found that the different nanoparticles including Ni, Pd, and alloyed Ni‐Pd showing different chemo‐selectivity and catalytic activity in the reaction.     

The Use of Laser Induced Breakdown Spectroscopy (LIBS) to Study Catalyst Deactivation of V2O5/γ‐Al2O3 as Compared to Inductively Coupled Plasma Optical Emission Spectrometry

Laser Induced Breakdown Spectroscopy (LIBS) method is introduced as a novel approach in this work to study catalyst deactivation of V₂O₅/γ‐‐Al₂O₃ for gas‐phase dehydration of glycerol and producing acrolein. The LIBS results of V₂O₅/γ‐Al₂O₃ samples are compared with those data that are obtained by Inductively Coupled Plasma Optical Emission Spectrometry (ICP‐OES). Experimental data of LIBS data specify that line intensities of vanadium are decreased by deactivation of V₂O₅/γ‐Al₂O₃ catalyst. A comparison between the results of LIBS test as well as ICP‐OES analysis shows that the amount of vanadium is decreased in the catalyst. Moreover, coke formation changes the surface of the catalyst. The results of deactivation of V₂O₅/γ‐Al₂O₃ are also compared with Pd/C catalyst deactivation.     

Palladium nanoparticles‐decorated triethanolammonium chloride ionic liquid‐modified TiO2 nanoparticles (TiO2/IL‐Pd): A highly active and recoverable catalyst for Suzuki–Miyaura cross‐coupling reaction in aqueous medium

In this work, an easily obtained procedure was successfully implemented to prepare novel palladium nanoparticles decorated on triethanolammonium chloride ionic liquid‐functionalized TiO₂ nanoparticles [TiO₂/IL‐Pd]. Different methods were carried out for characterizations of the synthesized nanocatalyst (HR‐TEM, XPS, XRD, FE‐SEM, EDX, FT‐IR and ICP). TiO₂/IL‐Pd indicated good catalytic activity for the Suzuki–Miyaura cross‐coupling reaction of arylboronic acid with different aryl halides in aqueous media at ambient temperature. The recycled catalyst was investigated with ICP to amount of Pd leaching after 6 times that had diminished slightly, Thus, was confirmed that the nanocatalyst has a good sustainability for C–C Suzuki–Miyaura coupling reaction. The catalyst can be conveniently separated by filtration of the reaction mixture and reused for 6 times without significant loss of its activity. It supplies an environmentally benign alternative path to the existing protocols for the Suzuki–Miyaura reaction.     

Synthesize,Characterization and Application of Phosphine‐free Polymer Supported Palladium Nanoparticles as Effective Catalyst in Suzuki‐Miyaura Cross‐coupling Reactions

Heterogeneous catalysts were developed by supporting palladium nanoparticles on modified cross‐linked polyacrylamide and successfully applied in Suzuki‐Miyaura cross‐coupling reactions. These catalysts are stable to air and moisture, and no sign of metal leaching was detected during the reactions as judged by elemental analysis of palladium by ICP‐OES technique and hot filtration test, which demonstrates the heterogeneous character of the catalysts. High yields of desired products were resulted by using these phosphine‐free catalysts at temperatures below 80 °C without aid of any additional ligands. The heat stability of the catalysts at the operating temperature was confirmed by thermogravimetric analysis (TGA). These catalysts are easy to use and cost effective. They can be recovered from reaction mixture by a simple filtration and reused in more successive reactions without significant loss in activity. The catalyst activity was restored by an ultrasonication program after deactivation in 10 cycles.     

Pd‐ Dithizone grafted onto magnetic nanoparticles and study of its catalyticactivity in C‐C and C‐N coupling reactions

In this paper, we report a simple, facile and efficient method for the synthesis of Fe₃O₄/SiO₂‐DTZ‐Pd. The immobilized palladium was an efficient catalyst without addition of phosphine ligands for Stille, Heck and N‐arylation reactions. This method has some advantages such as high yields and easy work up of products. In addition, the catalyst can be recovered using a magnet and reused several times without significant loss of its catalytic activity. This catalyst was characterized by various physico‐chemical techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD) and inductively coupled plasma (ICP).     

Synthesis of α‐(Fluorophenyl)pyridine by Palladium‐Catalyzed Cross‐Coupling Reaction

A series of α‐(fluoro‐substituted phenyl)pyridines have been synthesized by means of a palladium‐catalyzed cross‐coupling reaction between fluoro‐substituted phenylboronic acid and 2‐bromopyridine or its derivatives. The reactivities of the phenylboronic acids containing di‐ and tri‐fluoro substituents with α‐pyridyl bromide were investigated in different catalyst systems. Unsuccessful results were observed in the Pd/C and PPh₃ catalyst system due to phenylboronic acid containing electron‐withdrawing F atom(s). For the catalyst system of Pd(OAc)₂/PPh₃, the reactions gave moderate yields of 55% –80%, meanwhile, affording 10% –20% of dimerisation (self‐coupling) by‐products, but trace products were obtained in coupling with 2,4‐difluorophenylboronic acids because of steric hinderance. Pd(PPh₃)₄ was more reactive for boronic acids with sterically hindering F atom(s), and the coupling reactions gave good yields of 90% and 91% without any self‐coupling by‐product.     

The reduction of 4‐nitrophenol and 2‐nitroaniline by palladium catalyst based on a KCC‐1/IL in aqueous solution

KCC‐1/IL/Pd NPs can used as an excellent support for the synthesis of highly sparse homogeneous catalyst. KCC‐1 has high surface area that was functionalized with ionic liquid phase acting as the strong performers so that the Pd catalyst was well‐dispersed without aggregation on the framework of the KCC‐1/IL. This nano catalyst was specified by TGA, XRD, TEM, SEM, FT‐IR, and ICP. For reduction of 2‐nitroaniline and 4‐nitrophenol used from the KCC‐1/IL/Pd NPs as a green catalyst that showed excellent catalytic activities. Compared with the traditional substrate, KCC‐1 substantially increases protection and the accessibility of the nanoparticle sites due to its three dimensional hierarchical structure.     

Pd‐SBT@MCM‐41: As an efficient,stable and recyclable organometallic catalyst for C‐C coupling reactions and synthesis of 5‐substituted tetrazoles

A palladium S‐benzylisothiourea complex was anchored on functionalized MCM‐41 (Pd‐SBT@MCM‐41) and applied as efficient and reusable catalyst for the synthesis of 5‐substituted 1H –tetrazoles using [2 + 3] cycloaddition reaction of various organic nitriles with sodium azide (NaN₃) in poly(ethylene glycol) (PEG) as green solvent. Also this catalyst was applied as an versatile organometallic catalyst for Suzuki cross‐coupling reaction of aryl halides and phenylboronic acid (PhB(OH)₂) or sodium tetraphenyl borate (NaB(Ph)₄). This nanocatalyst was characterized by thermal gravimetric analysis (TGA), X‐ray Diffraction (XRD), scanning electron microscopy (SEM), inductively Coupled Plasma (ICP) and N₂ adsorption–desorption isotherms techniques. Recovery of the catalyst is easily achieved by centrifugation for several consecutive runs.     

Pd nanoparticles immobilized on boehmite by using tannic acid as structure-directing agent and stabilizer: a high performance catalyst for hydrogenation of olefins

Boehmite-supported Pd nanoparticles (Pd–TA–boehmite) were successfully synthesized by a hydrothermal method using tannic acid as the structure-directing agent as well as stabilizer. The physicochemical properties of the Pd–TA–boehmite catalyst were well characterized by XPS, XRD, N₂ adsorption/desorption, and TEM analyses. Catalytic hydrogenation of olefins was used as the probe reaction to evaluate the activity of the Pd–TA–boehmite catalyst. For comparison, the Pd–boehmite catalyst prepared without tannic acid was also employed for olefin hydrogenation. For all the investigated substrates, the Pd–TA–boehmite catalyst exhibited superior catalytic performance than the Pd–boehmite catalyst. For the example of hydrogenation of allyl alcohol, the initial hydrogenation rate and selectivity of the Pd–TA–boehmite catalyst were 23,520 mol/mol h and 99 %, respectively, while those of the Pd–boehmite catalyst were only 14,186 mol/mol h and 93 %, respectively. Additionally, the hydrogenation rate of the Pd–TA–boehmite catalyst could still reach 20,791 mol/mol h at the 7th cycle, which was much higher than that of the Pd–boehmite catalyst (5,250 mol/mol h) at the 4th cycle, thus showing an improved reusability.