Dual Gold Catalysis: σ,π‐Propyne Acetylide and Hydroxyl‐Bridged Digold Complexes as Easy‐To‐Prepare and Easy‐To‐Handle Precatalysts

A series of dinuclear gold σ,π‐propyne acetylide complexes were prepared and tested for their catalytic ability in dual gold catalysis that was based on the reaction of an electrophilic π‐complex of gold with a gold acetylide. The air‐stable and storable catalysts can be isolated as silver‐free catalysts in their activated form. These dual catalysts allow a fast initiation phase for the dual catalytic cycles without the need for additional additives for acetylide formation. Because propyne serves as a throw‐away ligand, no traces of the precatalyst are generated. Based on the fast initiation process, side products are minimized and reaction rates are higher for these catalysts. A series of test reactions were used to demonstrate the general applicability of these catalysts. Lower catalyst loadings, faster reaction rates, and better selectivity, combined with the practicability of these catalysts, make them ideal catalysts for dual gold catalysis.     

费托合成:SiO_2和Al_2O_3负载的Co_2C催化剂的表征和评价

采用CO碳化SiO2和Al3O4负载的Co(NO3)2的方法制备了SiO2和Al3O4负载的Co2C催化剂,采用N2物理吸附、X射线衍射和H2-程序升温还原技术对催化剂进行了表征,并用于催化费托合成反应中.结果显示,需要较长碳化时间才可合成负载的Co2C催化剂;所制催化剂表现出CO加氢生成高碳醇的催化性能,其原因可能在于催化剂表面存在的金属Co物种使CO解离,表面Co物种有利于CO插入,从而导致醇的生成,但体相Co2C则不具有催化活性.     

金/钯双金属纳米颗粒协同催化酰胺和醇间氢自转移反应中路易斯酸驱动反应路径

金属纳米颗粒,特别是金和它的双金属纳米颗粒作为强大的绿色催化剂广泛用于有机合成反应中。在一个反应体系中使用2个不同催化剂(如协同催化),在均相催化中是一个很好的策略。然而,这种方法仍在发展中。最近我们发现,金/钯双金属纳米颗粒与路易斯酸的协同催化体系可用于伯胺的N-烷基化：即酰胺与醇之间的氢自转移反应。我们详细报道了路易斯酸对该氢自转移反应的影响。结果表明,所选的路易斯酸不仅影响生成目标产物的反应路径,而且影响生成多个中间体和副产物的反应路径。弱的路易斯酸,如三氟甲磺酸碱土金属盐,非常适合酰胺的N-烷基化反应。     

Synthesis of poly(urethane‐imide) using aromatic secondary amine‐blocked polyurethane prepolymer

A set of poly(urethane‐imide)s were prepared using blocked Polyurethane (PU) prepolymer and pyromellitic dianhydride (PMDA). The PU prepolymer was prepared by the reaction of polyether glycol and 2,4‐tolylene diisocyanate, and end capped with N‐methyl aniline. The PU prepolymer was reacted with PMDA until the evolution of carbon dioxide ceased. The effect of tertiary amine catalysts, organo tin catalysts, solvents, and reaction temperature were studied and compared with the poly(urethane‐imide) prepared using phenol‐blocked PU prepolymer. N‐methyl aniline blocked PU prepolymer gave a higher molecular weight poly(urethane‐imide) at a lower reaction temperature in a shorter time. Amine catalysts were found to be more efficient than organo tin catalysts. The reaction was favorable in particular with N‐ethylmorpholine and diazabicyclo(2.2.2)octane (DABCO) as catalysts, and dimethylpropylene urea as a reaction medium. The poly(urethane‐imide)s were characterized by FTIR, GPC, TGA, and DSC analyses. The molecular weight decreased with an increase in reaction temperature. The thermal stability of the PU was found to increase by the introduction of imide component. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4032–4037, 2000     

Study on Synthesis,Characteristics and Catalysis Properties of Novel Chiral Metal Complexes Catalysts for 1,3‐Dipolar Cycloaddition Reactions of Nitrone with Electron‐Rich Alkene

As a new class of potential catalysts for 1,3‐dipolar cycloaddition reactions, fourteen L‐amino acid Schiff base Cu(II) and Ti(IV) complexes were synthesized, characterized, and evaluated for their catalytic activities in the reaction between C,N‐diphenylnitrone and electron‐rich ethyl vinyl ether under both homogeneous and in situ conditions. The methods for preparation and utilization of the catalysts were elucidated in detail, and the results of the catalytic reactions were described and discussed as well. Excellent reaction results were found in the presence of some catalysts (20 mol%) with > 90% endo‐isoazolidines produced, compared with predominantly exo‐isoazolidine produced without a catalyst. In addition, the reaction rate is found to be enhanced remarkably by a Cu(II) complex Schiff base catalyst at room temperature.     

First Pre‐Functionalised Polymeric Aromatic Framework from Mononitrotetrakis(iodophenyl)methane and its Applications

Starting from mononitrotetrakis(iodophenyl)methane as monomer, we report the preparation of the first pre‐functionalised porous aromatic frameworks (PAFs) and their application as supports for organometallic catalysts. Neutral coordinate imino‐pyridine Schiff base ( PAF‐NPy ) or chiral bis‐amino ( PAF‐NPro ) ligands were obtained by post‐synthetic treatment of PAF‐NH₂ and treated with copper(I) or rhodium(I) to yield the corresponding supported transition‐metal catalysts. The as‐prepared PAF‐NN‐M catalysts exhibited activity and selectivity similar to that of the corresponding homogeneous catalysts and were easily removed from reaction media and recycled without loss of activity or selectivity.     

离子液体催化甘油和尿素合成甘油碳酸酯

将一系列酸性、碱性和中性的功能化离子液体用于催化甘油和尿素合成甘油碳酸酯。结果表明,中性离子液体表现出更高的催化活性。离子液体阳离子和阴离子的协同效应促进了反应的进行,离子液体阳离子的正电性活化尿素,阴离子的负电性活化甘油,并且催化剂酸碱位点的平衡对催化反应过程也有一定的影响。此外,离子液体可以实现回收利用至少五次,且催化活性基本不变。采用功能化离子液体替代传统金属催化剂,减少了不可再生资源的利用,且所用原料为廉价易得的生物基原料,过程中也不使用有机溶剂,环境友好。     

Synthesis and characterization of iron‐ and nitrogen‐functionalized graphene catalysts for oxygen reduction reaction

Iron‐ and nitrogen‐functionalized graphene (Fe‐N‐G), as well as iron‐ and nitrogen‐functionalized oxidized graphene (Fe‐N‐Gox) catalysts were synthesized as non‐noble metal electrocatalysts for oxygen reduction reaction (ORR). The physical properties of the resultant catalysts were characterized using nitrogen adsorption measurements, X‐ray diffraction, Raman and X‐ray photoelectron spectroscopies and transmission electron microscopy. Subsequently, ORR activities of the catalysts were determined electrochemically using a conventional three‐electrode cell via cyclic voltammetry with a rotating disc electrode, the results of which indicated that the synthesized catalysts had a marked electrocatalytic activity towards ORR in acid media. Among the synthesized catalysts, that functionalized using 2,4,6‐tris(2‐pyridyl)‐1,3,5‐triazine as nitrogen source had the highest electrocatalytic activity with the highest onset potential (0.98 V/SHE) and limiting current density (5.12 mA cm⁻²). The findings are particularly important to determine a non‐precious metal catalyst for ORR activity in fuel cells.     

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.     

Metalloporphyrin‐Based Hypercrosslinked Polymers Catalyze Hetero‐Diels–Alder Reactions of Unactivated Aldehydes with Simple Dienes: A Fascinating Strategy for the Construction of Heterogeneous Catalysts

We describe a novel and intriguing strategy for the construction of efficient heterogeneous catalysts by hypercrosslinking catalyst molecules in a one‐pot Friedel–Crafts alkylation reaction. The new hypercrosslinked polymers (HCPs) as porous solid catalysts exhibit the combined advantages of homogeneous and heterogeneous catalysis, owing to their high surface area, good stability, and tailoring of catalytic centers on the frameworks. Indeed, a new class of metalloporphyrin‐based HCPs were successfully synthesized using modified iron(III) porphyrin complexes as building blocks, and the resulting networks were found to be excellent recyclable heterogeneous catalysts for the hetero‐Diels–Alder reaction of unactivated aldehydes with 1,3‐dienes. Moreover, this new strategy showed wide adaptability, and many kinds of homogeneous‐like solid‐based catalysts with high catalytic performance and excellent recyclability were also constructed.     

磁性纳米复合氧化物固体酸催化剂的制备及酯化性能

固体酸催化剂的无腐蚀、环境友好和可循环使用等特点使其成为无机液体酸的最佳替代物.磁性纳米固体酸具有优于常规固体酸催化剂的催化活性及分离简单的特性.用共沉淀法分别合成了一系列三组分TiO2-Al2O3-Fe3O4(TAF)和CeO2-Al2O3-Fe3O4(CAF)及四组分ZrO2--Al2O3-Fe3O4(ZACF)磁性纳米复合氧化物固体酸催化剂,通过电感耦合等离子体原子发射光谱、比表面积测定、X射线衍射、透射电镜、热重分析和红外光谱等对其进行了表征,并利用酯化反应作为探针反应评价了其催化性能.结果表明,合成的磁性纳米固体酸催化剂在酯化反应中表现出很好的催化活性.     

Synthesis and catalytic application of Pd complex catalysts: Atom‐efficient cross‐coupling of triarylbismuthines with haloarenes and acid chlorides under mild conditions

Palladium‐catalysed cross‐coupling reactions are some of the most frequently used synthetic tools for the construction of new carbon–carbon bonds in organic synthesis. In the work presented, Pd(II) complex catalysts were synthesized from palladium chloride and nitrogen donor ligands as the precursors. Infrared and ¹H NMR spectroscopic analyses showed that the palladium complexes were formed in the bidentate mode to the palladium centre. The resultant Pd(II) complexes were tested as catalysts for the coupling of organobismuth(III) compounds with aryl and acid halides leading to excellent yields with high turnover frequency values. The catalysts were stable under the reaction conditions and no degradation was noticed even at 150°C for one of the catalysts. The reaction proceeds via an aryl palladium complex formed by transmetallation reaction between catalyst and Ar₃Bi. The whole synthetic transformation has high atom economy as all three aryl groups attached to bismuth are efficiently transferred to the electrophilic partner.     

Discovery and Application of Doubly Quaternized Cinchona‐Alkaloid‐Based Phase‐Transfer Catalysts

We report the discovery of novel N,N′‐disubstituted cinchona alkaloids as efficient phase‐transfer catalysts for the assembly of stereogenic quaternary centers. In comparison to traditional cinchona‐alkaloid‐based phase‐transfer catalysts, these new catalysts afford substantial improvements in enantioselectivity and reaction rate for intramolecular spirocyclization reactions with catalyst loadings as low as 0.3 mol % under mild conditions.     

Synthesis and characterization of Pd(II) complexes of 2‐ and 3‐thiophenecarbaldehyde immobilized on silica obtained from sepiolite

Silica obtained by acid treatment of sepiolite was used as a support for catalysts consisting of palladium complexes of 2‐ and 3‐thiophenecarbaldehyde. The support and the catalysts were characterized by X‐ray diffraction, and solid‐state ²⁹Si and ¹³C nuclear magnetic resonance spectroscopies. The supported palladium catalysts were used in the Suzuki reaction of bromobenzene with phenylboronic acid. Copyright © 2013 John Wiley & Sons, Ltd.     

Silicon‐grafted Ag/AgX/rGO nanomaterials (X = Cl or Br) as dip‐photocatalysts for highly efficient p‐nitrophenol reduction and paracetamol production

In this work, plasmonic Ag/AgX/rGO (X = Cl or Br) nano‐photocatalysts were grafted with silicon by adding trimethylsilyl chloride as silicon precursor. The synthesized Ag/AgX/rGO‐Si hybrids showed a large improvement of photocatalytic activity towards the synthesis of p‐aminophenol (PAP) as well as paracetamol (acetaminophen; APAP) through the photoreduction of p‐nitrophenol (PNP). The prepared catalysts Ag/AgX/rGO were characterized using SEM, XRD, FTIR and the reduction reaction of p‐nitrophenol was monitored by UV–Vis measurements, GC/MS and ¹HNMR data. From the results, it was demonstrated that the rate order of reduction process of the PNP to PAP and to APAP under visible light irradiation of the samples was as follows; Ag/AgBr/rGO‐Si > Ag/AgCl/rGO‐Si > Ag/AgBr/rGO > Ag/AgCl/rGO. The reaction mechanism had been postulated that was supported with the spectroscopic data. In addition, the catalysts were recovered from the reaction medium and re‐used in three cycles that indicated the reusability and stability of the catalysts. This study was featured by the following; i) fast reaction, ii) the reduction of p‐nitrophenol to paracetamol was performed in a facile one‐pot reaction compared to previous approaches that tends to reduce the production cost, and iii) investigations on the catalytic properties of Ag/AgX/rGO in organic transformations open the door to find a benefice of these catalysts in other organic reactions and in the development in the synthesis of pharmaceutical products.     

Highly efficient and excellent reusable catalysts of molybdenum(VI) complexes grafted on ZPS‐PVPA for epoxidation of olefins with tert‐BuOOH

Four new kinds of heterogeneous catalysts for olefins epoxidation were obtained by grafting diamines on organic polymer–inorganic hybrid material, zirconium poly (styrene‐phenylvinylphosphonate)‐phosphate (ZPS‐PVPA), and subsequently coordinating with Schiff base Mo(VI) complexes. The catalysts were characterized by IR, XPS, SEM and TEM. All catalysts were evaluated through the epoxidation of olefins using tert‐BuOOH as oxidant. The heterogeneous catalysts possess the advantages of high conversion, selectivity and excellent reusability. The catalysts were easily separated from the reaction systems and could be reused 13 times without significant loss of catalytic activity. Copyright © 2010 John Wiley & Sons, Ltd.     

Catalytic C−H Trifluoromethoxylation of Arenes and Heteroarenes

The intermolecular C?H trifluoromethoxylation of arenes remains a long‐standing and unsolved problem in organic synthesis. Herein, we report the first catalytic protocol employing a novel trifluoromethoxylating reagent and redox‐active catalysts for the direct (hetero)aryl C?H trifluoromethoxylation. Our approach is operationally simple, proceeds at room temperature, uses easy‐to‐handle reagents, requires only 0.03 mol % of redox‐active catalysts, does not need specialized reaction apparatus, and tolerates a wide variety of functional groups and complex structures such as sugars and natural product derivatives. Importantly, both ground‐state and photoexcited redox‐active catalysts are effective. Detailed computational and experimental studies suggest a unique reaction pathway where photoexcitation of the trifluoromethoxylating reagent releases the OCF₃ radical that is trapped by (hetero)arenes. The resulting cyclohexadienyl radicals are oxidized by redox‐active catalysts and deprotonated to form the desired products of trifluoromethoxylation.     

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.     

Surface Functionalization of Magnetite Nanoparticles with Sulfonic Acid and Heteropoly Acid: Efficient Magnetically Recoverable Solid Acid Catalysts

New magnetically recoverable solid acid catalysts for acid‐catalyzed reactions were designed via the surface chemical functionalization of silica‐coated magnetite nanoparticles (SCMNPs) with sulfonic acid groups. First, the SCMNPs were covalently functionalized with 3‐aminopropyl groups to achieve Amp‐SCMNPs. Then, reaction of the Amp‐SCMNPs with 1,4‐butane sultone followed by acidification with phosphotungstic acid (HPW) or diluted sulfuric acid produced magnetically recoverable solid acid catalysts, HPW‐ampsul‐SCMNPs and H‐ampsul‐SCMNPs, respectively. Both catalysts were characterized by various physicochemical analyses such as Fourier transform infrared (FT‐IR) and inductively coupled plasma‐optical emission (ICP‐OES) spectroscopies, vibrating sample magnetometry (VSM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD), and energy‐dispersive X‐ray (EDX) analyses. Finally, the catalytic activities of the prepared catalysts were examined in the esterification of acetic acid with butanol and acetalization of benzaldehyde with ethylene glycol. Excellent catalytic efficiencies were obtained in both cases. The catalysts were consecutively recovered and reused five times without significant loss of their activities.     

Catalytic Reduction of Molecular Dinitrogen to Ammonia and Hydrazine Using Vanadium Complexes

Newly designed and prepared vanadium complexes bearing anionic pyrrole‐based PNP‐type pincer and aryloxy ligands were found to work as effective catalysts for the direct conversion of molecular dinitrogen into ammonia and hydrazine under mild reaction conditions. This is the first successful example of vanadium‐catalyzed dinitrogen reduction under mild reaction conditions.