Chiral Jacobsen's catalyst immobilized on zinc poly(styrene‐phenylvinylphosphonate)‐phosphate functionalized by diamine as highly efficient and reusable catalyst for alkene epoxidation

Chiral Jacobsen's catalyst anchored on zinc poly(styrene‐phenylvinylphosphonate)‐phosphate (ZnPS‐PVPA) functionalized by diamines shows superior catalytic activities (conversion up to 99%; enantiomeric excess up to 99%) in the enantioselective epoxidations of unfunctional olefins with m ‐chloroperoxybenzoic acid and NaIO₄ as oxidants. The whole chiral salen Mn(III) catalyst, including the ZnPS‐PVPA support and the linker as well as chiral salen Mn ligand together contribute to the chirality of products. The heterogeneous catalyst has the potential for use in industry owing to superior stability (recycling nine times) and activity in large‐scale reactions (such as 200 times).     

Molybdenum hexacarbonyl supported on amine modified multi‐wall carbon nanotubes: an efficient and highly reusable catalyst for epoxidation of alkenes with tert‐butylhydroperoxide

In the present work, highly efficient epoxidation of alkenes catalyzed by Mo(CO)₆ supported on multi‐wall carbon nanotubes modified by 2‐aminopyrazine, APyz‐MWCNTs, is reported. The prepared catalyst was characterized by elemental analysis, scanning electron microscopy, FT IR and diffuses reflectance UV–vis spectroscopic methods. This new heterogenized catalysts, [Mo(CO)₆@APyz‐MWCNT], was used as a highly efficient catalyst for epoxidation of alkenes with tert‐BuOOH. This robust catalyst was reused several times without loss of its catalytic activity. Copyright © 2010 John Wiley & Sons, Ltd.     

Chiral electron deficient ruthenium helical coordination polymer as a catalyst for the epoxidation of substituted styrenes

An air and moisture stable ruthenium(Ⅲ) formate complex[Ru(HCO_2)Cl_2]_n has been synthesized and examined in the epoxidation of substituted styrenes.X-ray crystallographic data of this complex were determined and showed that the formate ligand coordinates to the ruthenium centers in a μ~2-η~2 fashion(syn,syn).Its asymmetric unit contains one Ru(Ⅲ) ion together with the half of a formate ligand and one chloride anion,which are bridged between the metal centers,forming a 1-D chain coordination polymer.This electron deficient helical coordination polymer was employed in the epoxidation of parafluorostyrene,affording the epoxide product in 92%yield.Natural chirality of this coordination polymer is applicable in asymmetric epoxidation reactions.     

Pd nanoparticles supported on amphiphilic porous organic polymer as an efficient catalyst for aqueous hydrodechlorination and Suzuki-Miyaura coupling reactions

Developing efficient and recyclable heterogeneous catalysts for organic reactions in water is important for the sustainable development of chemical industry. In this work, Pd nanoparticles supported on DABCO-functionalized porous organic polymer was successfully prepared through an easy copolymerization and successive immobilization method. Characterization results indicated that the prepared catalyst featured big surface area, hierarchical porous structure, and excellent surface amphiphilicity. We demonstrated the use of this amphiphilic catalyst in two case reactions, i.e. the aqueous hydrodechlorination and Suzuki-Miyaura coupling reactions. Under mild reaction conditions, the catalyst showed high catalytic activities for the two reactions. In addition, the catalyst could be easily recovered and reused for several times. Also, no obvious Pd leaching and aggregation of Pd nanoparticles occurred up during the consecutive reactions.     

Polymer‐supported macrocyclic Schiff base palladium complex as an efficient catalyst for the Heck reaction

A polymer‐supported macrocyclic Schiff base palladium complex has been synthesized. In the Heck reaction of aryl iodides and bromides with ethyl acrylate or styrene, the complex has been proved to give the corresponding products in good to excellent yields. The reaction proceeded smoothly in the presence of 0.5 mol% of catalyst in DMF within 1–4 h. Recycling studies have shown that the catalyst can be readily recovered and reused for four cycles with only a slightly decrease in its activity. Copyright © 2011 John Wiley & Sons, Ltd.     

Copper immobilized onto polymer‐coated magnetic nanoparticles as recoverable catalyst for ‘click’ reaction

Copper supported on polymer‐coated magnetic nanoparticles was designed and synthesized as a separable heterogeneous catalyst. The catalyst was fully characterized using several techniques such as Fourier transform infrared and energy‐dispersive X‐ray spectroscopies, scanning and transmission electron microscopies, X‐ray diffraction, vibrating sample magnetometry, thermogravimetric analysis and inductively coupled plasma atomic emission spectrometry. All results showed that copper was successfully supported on the polymer‐coated magnetic nanoparticles. Also, results showed that the synthesized material can be used as an efficient catalyst for the preparation of a series of 1,4‐disubstituted 1,2,3‐triazoles from corresponding halides, alkynes and sodium azide. The catalyst can be easily isolated from the reaction solution by applying an external magnet and reused for nine runs without any significant loss of catalytic activity.     

A new 2D cadmium coordination polymer based on hydroxyl-substituted benzenedicarboxylic acid as an effective heterogeneous catalyst for Knoevenagel condensation

A self-assembled new 2D cadmium network, [Cd (BDC-OH)(DMF)₂·DMF]_n (Cd-BDC-OH), was synthesized based on 2-hydroxyterephthalic acid (BDC-OH) ligand and utilized as a heterogeneous catalyst for Knoevenagel condensation. The structure was fully elucidated by single-crystal X-ray diffraction, Hirshfeld surface analysis, powder X-ray diffraction, field emission-scanning electron microscopy, Fourier transform-infrared spectroscopy and thermogravimetric analysis. The fabricated coordination polymer exhibited high catalytic activity under ambient conditions, and was used without significant drop in product yield in further cycles.     

Schiff base‐functionalized boehmite nanoparticle‐supported molybdenum and vanadium complexes: efficient catalysts for the epoxidation of alkenes

Boehmite nanoparticles, with high surface area and high degree of surface hydroxyl groups, were prepared via hydrothermal‐assisted sol–gel processing of aluminium 2‐butoxide. The produced powder was covalently functionalized with 3‐(trimethoxysilyl)propylamine, and then, in order to support vanadium oxosulfate and molybdenum hexacarbonyl complexes, all the terminal amine groups were changed to Schiff bases by refluxing with salicylaldehyde. These catalysts were applied in the epoxidation of cis‐cyclooctene and other olefins with tert‐BuOOH in CCl₄. The catalytic procedures for both catalysts were optimized for various parameters such as solvent and oxidant. Recycling experiments revealed that these heterogeneous nano‐catalysts could be repeatedly applied for the epoxidation of alkenes. Copyright © 2015 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.     

Heterogeneous Jacobsen's catalyst on alkoxyl‐modified zirconium poly (styrene‐phenylvinylphosphonate)‐phosphate (ZPS‐PVPA) for asymmetric epoxidation

Chiral Jacobsen's catalysts grafted onto alkoxyl‐modified ZPS‐PVPA exhibit excellent activities (conv%, up to 96; sele%, up to 96; ee%, up to >99) in the asymmetric epoxidations of unfunctionalized olefins. The superior stabilities and the comfortable dispositions in large‐scale reactions contribute to the potential applications in industry.     

Copper(I) and palladium nanoparticles supported on ethylenediamine‐functionalized cellulose as an efficient catalyst for the 1,3‐dipolar cycloaddition/direct arylation sequence

Cu(I) and nanoparticles of Pd supported on ethylenediamine‐functionalized cellulose as a novel bio‐supported catalyst was synthesized and characterized. The synthesized catalyst was found to be a highly efficient heterogeneous catalyst for the synthesis of 1,4,5‐trisubstituted 1,2,3‐triazoles through a sustainable 1,3‐dipolar cycloaddition/direct arylation sequence. The catalyst could be easily recovered by simple filtration and reused for at least five cycles without losing its activity. Copyright © 2014 John Wiley & Sons, Ltd.     

Synthesis and characterization of molybdenum (VI) complex immobilized on polymeric Schiff base-coated magnetic nanoparticles as an efficient and retrievable nanocatalyst in olefin epoxidation reactions

In this study, a new polymeric functionalized magnetic nanocatalyst containing a molybdenum Schiff base complex was prepared using a few consecutive steps. Poly (methylacrylate)-coated magnetic nanoparticles were synthesized via radical polymerization of methyl acrylate onto modified magnetic nanoparticles followed by the amidation of the methyl ester groups with hydrazine. Polymeric functionalization efficiently provides the advantage that more catalytic units can be grafted on the surface of magnetic nanoparticles. The functionalization process was continued with salicylaldehyde which introduced Schiff base groups on to the surface of the polymeric support. In the final step, the desired catalytic system was prepared via complexation of the Schiff base groups with MoO₂(acac)₂. The resulting nanoparticles were characterized by infrared spectroscopy, powder X-ray diffraction, scanning and transmission electron microscopy, elemental analysis, inductively coupled plasma optical emission spectrometry, vibrating sample magnetometry and thermogravimetric analysis. This heterogenized catalytic system was also found to be highly active, sustainable and recyclable nanocatalyst in alkene epoxidation. Eventually, the attractive features of the synthesized catalyst such as simple work-up, good stability, magnetic separation, high TOF and high surface area; make it appropriate for oxidation reactions.     

Palladium nanoparticles supported on mesoporous natural phosphate: An efficient recyclable catalyst for nitroarene reduction

We report the preparation of palladium nanoparticles supported on mesoporous natural phosphate (Pd@NP) using a wetness impregnation method. The prepared catalyst was characterized using various techniques. Furthermore, the reduction and preparation of the palladium nanoparticles was followed using UV–visible spectra. Based on the Scherrer equation, the crystallite size of the as‐synthesized palladium nanoparticles was 10.88 nm. The performance of the synthesized catalyst was investigated in the reduction of 4‐nitrophenol as a model substrate to 4‐aminophenol using NaBH₄ as a hydrogen source. Moreover, catalytic reduction of various nitroarenes was studied and monitored using UV–visible spectroscopy and gas chromatography. The Pd@NP catalyst showed a high activity for the selected reaction and could be recycled.     

Synthesis,characterization and catalytic performance of palladium supported on pyridine‐based covalent organic polymer for Suzuki‐Miyaura reaction

A bipyridine‐based covalent organic polymer (COP) was successfully synthesized by condensation of trimesoyl chloride (TMC) and 2,2′‐bipyridine‐5,5′‐diamine (Bpy) under ambient conditions. This material was modified by coordination of PdCl₂ to COP framework, affording a hybrid material, Pd@TMC‐Bpy COP, which was applied as a highly efficient heterogeneous catalyst for Suzuki‐Miyaura reaction under ligand‐free conditions in ethyl lactate. The catalyst could be reused for five times without obvious loss of its activity.     

Synergetic promotion of Ba, Cs and Cl to silver supported catalyst for butadiene epoxidation

Summary Ag/-Al₂O₃ catalysts promoted by Ba, Cs and Cl were prepared and evaluated for butadiene epoxidation. The results indicated that Cs could enhance butadiene conversion, Cl was favorable for improving the selectivity to vinyloxirane (VO), and Ba probably plays an important role for catalyst stability during the long time on stream operation.     

Preparation and characterization of Fe3O4@Boehmite core‐shell nanoparticles to support molybdenum or vanadium complexes for catalytic epoxidation of alkenes

Fe₃O₄ core nanoparticles were prepared via a solvothermal process, and then they were covered with a surface hydroxyl‐rich boehmite shell via the hydrothermal‐assisted sol–gel processing of aluminum 2‐propoxide. The outer surface of the boehmite shell was subsequently covalently functionalized with 3‐(tri‐methoxysilyl)‐propylamine or 3‐(tri‐methoxysilyl)‐propyl chloride, and the terminal chlorine groups were treated with imidazole. These compounds were used to support the hexa‐carbonyl molybdenum and oxo‐sulfato vanadium (IV) complexes. The supported catalysts were characterized by the FT‐IR, CHN, ICP, and TEM analysis techniques. They were then used in the epoxidation of cis‐cyclooctene. The catalytic procedures were optimized for different parameters such as the solvent, oxidant, and temperature. The reaction progress was investigated by the gas–liquid chromatography analysis. The catalysts used were simply recovered from the solution by applying a magnet, and recycling the experiments revealed that the heterogeneous nanocatalysts could be repeatedly used for the epoxidation of cis‐cyclooctene. The optimized conditions were also successfully used for the epoxidation of some other alkenes.     

Pd@tetrahedral hollow magnetic nanoparticles coated with N‐doped porous carbon as an efficient catalyst for hydrogenation of nitroarenes

Hollow magnetic nanoparticles (MNPs) with tetrahedral morphology were synthesized and then covered by a shell prepared by coating with melamine–formaldehyde followed by the introduction of glucose‐derived carbon. Subsequently, Pd nanoparticles were immobilized and the core–shell nanocomposite was carbonized. The obtained magnetic catalyst was successfully applied for the hydrogenation of nitroarenes in aqueous media. To investigate the effects of the morphology of MNPs, the nature of carbon shell, and the order of incorporation of Pd nanoparticles, several control catalysts, including the MNPs with different morphologies (disc‐like and cylinder); MNPs coated with different shells (sole glucose‐derived carbon or melamine–formaldehyde carbon shell); and a nanocomposite, in which Pd was immobilized after carbonization, were prepared and examined as catalyst for the model reaction. To justify the observed different catalytic activities of the catalysts, their Pd loadings, leaching, and specific surface areas were compared. The results confirmed that tetrahedral MNPs coated with porous N‐rich carbon shell exhibited the best catalytic activity. The high catalytic activity of this catalyst was attributed to its high surface area and the interaction of N‐rich shell with Pd nanoparticles that led to the higher Pd loading and suppressed Pd leaching.     

多孔有机聚合物负载钯作为高效C-C偶联反应多相催化剂

Pd催化的C-C均相偶联反应,如Suzuki,Heck和Sonogashira广泛应用于有机合成、药物化学、材料科学等领域.均相催化剂具有难分离和不易循环利用的缺点,因而其应用有所受限.因此,开发具有高稳定性和高活性以及可循环性的Pd负载的多相催化剂具有重要意义.多孔有机聚合物具有独特的多级孔结构以及良好的稳定性,因而为制备新型的多相催化剂提供了可能.本文将乙烯基修饰的1,10-菲罗啉有机配体与二乙烯基苯共聚得到了菲罗啉功能化的多孔有机聚合物(PCP-Phen),负载Pd(OAC)2后所制催化剂(Pd/PCP-Phen)在Suzuki,Heck和Sonogashira等偶联反应中表现出优异的活性、选择性和稳定性.固体核磁和红外结果表明所合成的多孔有机聚合物具有1,10-菲罗啉有机配体;热重分析显示该聚合物具有较高的热稳定性;N2吸附测试表明该多孔有机聚合物及其钯负载物均具有丰富的介孔结构(11.2和7.3 nm)和大的比表面积;扫描电镜和透射电镜结果确也证实了它们具有丰富的介孔结构.X射线光电子能结果表明,Pd/POP-Phen催化剂中Pd 3d5/2和Pd 3d3/2的结合能分别为337.6和343.1 eV,略低于Pd(OAc)2的(338.6和343.8 eV).同时,该催化剂的N 1s结合能为400.0 eV,高于POP-Phen的399.3 eV.由此可见,该催化剂中菲罗啉有机配体与Pd物种有很强的配位作用.将得到的Pd/POP-Phen催化剂用于Suzuki,Sonogashira以及Heck反应.对于Suzuki反应,当以溴苯和苯硼酸为底物,乙醇和水(2∶3)为溶剂时,反应30 min联苯的产率高于99％;而在菲罗啉和醋酸钯(Pd/Phen)混合均相催化剂作用下,同样条件下转化率仅为1.7％.可见,Pd/POP-Phen多相催化剂在Suzuki反应中的催化活性高于均相催化剂.更为重要的是,该催化剂在循环使用五次后并未见明显的失活,且在反应液中也未检测到Pd,说明反应中金属物种基本上没有流失,与Pd/POP-Phen 多相催化剂的高稳定性一致.当将反应物扩展到多种不同底物时,Pd/POP-Phen催化剂均显示出非常优异的催化性能.在Sonogashira和Heck反应中,该多相催化剂也有非常好的催化性能.在碘苯和苯乙炔为反应物的Sonogashira反应中,于120℃进行30 min后,转化率即可达99％以上,高于Pd/Phen均相催化剂(93％);且该反应在没有CuI参与下也可以进行,从而避免了副产物二苯炔的形成.在碘苯和丙烯酸甲酯为底物的Heck反应中,于130℃只需反应20 min转化率可达到＞99％,也优于相应的均相催化剂.循环实验表明,该催化剂具有很高的稳定性.Pd/POP-Phen多相催化剂表现出高于均相催化剂的活性,主要原因归于催化剂孔道中相对较高的反应物浓度.在多相催化反应中,因为其丰富的多孔结构对反应物具有很强的富集作用,从而使得多相催化剂里的反应物浓度大大高于均相催化剂.例如,在Suzuki反应中,溴苯在多相催化剂中的浓度是均相催化体系的14倍.     

Resin‐supported palladium nanoparticles as recyclable catalyst for the hydrodechlorination of chloroarenes and polychlorinated biphenyls

This study focuses on the hydrodechlorination of chlorinated arenes as well as polychlorinated biphenyls (PCBs) utilizing a resin‐supported Pd(0) catalyst. Bearing in mind the dangers associated with toxic PCBs, treatment of the remnants of industrial wastes containing PCB congeners is indispensable. One such method is reductive hydrodechlorination. Instead of utilizing traditional sources of hydrogen, ammonium formate is used for in situ hydrogen generation. Moreover, palladium nanoparticles are supported on an anionic exchange resin which makes the process recyclable with a negligible change of yield after recycling experiments. The catalyst is demonstrated in the hydrodechlorination of a wide range of chlorinated compounds and PCB congeners including aroclors 1242, 1248 and 1254. Copyright © 2016 John Wiley & Sons, Ltd.     

Polymer‐supported zirconocene catalyst for ethylene polymerization

The use of crosslinked poly(styrene‐co‐4‐vinylpyridine) having functional groups as the support for zirconocene catalysts in ethylene polymerization was studied. Several factors affecting the activity of the catalysts were examined. Conditions like time, temperature, Al/N (molar ratio), Al/Zr (molar ratio), and the mode of feeding were found having no significant influence on the activity of the catalysts, while the state of the supports had a great effect on the catalytic behavior. The activity of the catalysts sharply increased with either the degree of crosslinking or the content of 4‐vinylpyridine in the support. Via aluminum compounds, AlR₃ or methylaluminoxane (MAO), zirconocene was attached on the surface of the support. IR spectra showed an intensified and shifted absorption bands of C N in the pyridine ring, and a new absorption band appeared at about 730 cm⁻¹ indicating a stable bond Al N formed in the polymer‐supported catalysts. The formation of cationic active centers was hypothesized and the performance of the polymer‐supported zirconocene was discussed as well. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 37–46, 1999