Solid-supported palladium nano and microparticles: an efficient heterogeneous catalyst for ligand-free Suzuki-Miyaura cross coupling reaction

Solid-supported nano and microparticles of Pd(0) (SS-Pd) were prepared and used as heterogeneous catalysts for Suzuki-Miyaura cross coupling reactions of aryl halides (chloro, bromo and iodo) and phenyl boronic acid under mild and ligand-free conditions. Scanning electron microscope (SEM) and UV-vis based studies were performed to observe the distribution of nano and microparticles of palladium over solid surface and their oxidation states. In addition, the catalyst could be reused up to seven runs without significant loss of activity and stable enough under moist conditions.     

Solid-supported Pd(0): an efficient heterogeneous catalyst for aerobic oxidation of benzyl alcohols into aldehydes and ketones

Solid-supported nano- and microparticles of Pd(0) (SS-Pd) were used as heterogeneous catalysts for aerobic oxidation of benzyl alcohols. Primary and secondary benzyl alcohols gave the corresponding products in good yields. In addition, the catalysts could be reused up to five runs without significant loss of activities.     

Pd/Nb2O5: efficient supported palladium heterogeneous catalyst in the production of key intermediates for the synthesis of ‘sartans’ via the Suzuki reaction

Pd/Nb₂O₅ was prepared, characterized and tested in Suzuki-Miyaura cross-coupling reactions under ligand-free conditions. High yields and selectivities were observed within short reaction times and very low palladium loadings.     

MCM‐41‐supported mercapto palladium(0) complex: an efficient and recyclable catalyst for the heterogeneous Stille coupling reaction

The Stille cross‐coupling reaction of organostannanes with aryl halides was achieved in the presence of a catalytic amount of MCM‐41‐supported mercapto palladium(0) complex (1 mol%) in DMF? H₂O (9:1) under air atmosphere in good to high yields. This MCM‐41‐supported palladium catalyst can be reused at least 10 times without any decrease in activity. Copyright © 2009 John Wiley & Sons, Ltd.     

Solid supported Pd(0): an efficient recyclable heterogeneous catalyst for chemoselective reduction of nitroarenes

Solid supported palladium(0) (SS-Pd) catalyzed highly chemoselective reduction of nitroarenes to the corresponding anilines was accomplished under a milder reaction condition. This catalyst showed high compatibility with various reducing agents (NaBH₄, Et₃SiH, and NH₂NH₂·H₂O) and a large number of reducible functional groups such as sulfonamide, amides, carboxylic acid, ester, alcohol, halide, hetero cycle, nitrile, alkene, carbonyl, O-benzyl, and N-benzyl were tolerated. Most of the reactions were clean and high yielding. The SS-Pd catalyst could be recycled up to seven runs without significant loss of activity.     

Aminoarenethiolato-copper(I) as (pre-)catalyst for the synthesis of diaryl ethers from aryl bromides and sequential C-O/C-S and C-N/C-S cross coupling reactions

A small library of 2-aminoarenethiolato-copper(I) (CuSAr) complexes was tested as (pre-)catalysts in the arylation reaction of phenols with aryl bromides. These copper(I) (pre-)catalysts are thermally stable, soluble in common organic solvents, and allow reactions of 6 h at 160 °C with low catalyst loadings of 2.5 mol %. Among the (pre-)catalysts screened, 2-[(dimethylamino)methyl]benzenethiolato-copper(I) (1c) led to the best results and provided good to excellent yields of various substituted diaryl ethers. Mechanistic studies showed that at early stages of the C-O coupling reaction the CuSAr complex is converted into CuBr(PhSAr) via selective coupling of the monoanionic arenethiolato ligand with phenyl bromide with formation of CuBr. In addition, the first results are shown involving a multi-component reaction (MCR) protocol for the in situ synthesis of propargylamines and their subsequent conversion involving a C-O cross coupling reaction. Furthermore, two examples of sequential C-O/C-S and C-N/C-S cross coupling reactions have been carried out on the same dihalo-pyridine substrate in a one-pot process with the same (CuSAr) (pre-)catalyst (overall yields 40-80%).     

功能化MCM-41负载双齿氮钯催化剂的制备及其在Suzuki偶联中的应用

首先胺功能化修饰介孔材料MCM-41,再与二-(吡啶-2-基-)甲酮缩合成席夫碱,最后通过Pd(OAc)2配位制备了MCM-41负载双齿氮钯配合物,采用X射线衍射(XRD)以及X射线光电子能谱(XPS)对其结构表征.该负载催化剂在以二甲苯为溶剂,K2CO3为碱以及n-Bu4NF用作添加剂的Suzuki偶联中表现出优越的催化性能.     

A novel MCM-41-supported sulfur palladium(0) complex catalyst for Sonogashira coupling reaction

A novel MCM-41-supported sulfur palladium(0) complex was conveniently prepared from commercially available and cheap γ-mercaptopropyltriethoxysilane via immobilization on MCM-41, followed by reacting with palladium chloride and then the reduction with hydrazine hydrate. This complex exhibited excellent performance in Sonogashira coupling reaction.     

MCM-41-supported bidentate phosphine palladium(0) complex as an efficient catalyst for the heterogeneous Stille reaction

A Stille coupling reaction of organostannanes with organic halides has been developed in the presence of a catalytic amount of MCM-41-supported bidentate phosphine palladium(0) complex (0.5 mol %) in DMF/H₂O (9:1) under air atmosphere in high yields. This polymeric palladium catalyst exhibits higher activity than Pd(PPh₃)₄ and can be reused at least 10 times without any decrease in activity.     

MCM-41-supported bidentate phosphine palladium(0) complex: a highly active and recyclable catalyst for the Sonogashira reaction of aryl iodides

The first MCM-41-supported bidentate phosphine palladium(0) complex has been prepared. This complex is a highly efficient catalyst for Sonogashira reaction and can be reused at least 10 times without any decrease in activity.     

A facile synthesis of terminal arylacetylenes via Sonogashira coupling reactions catalyzed by MCM-41-supported mercapto palladium（0） complex

A variety of terminal arylacetylenes have been conveniently synthesized in good to high yields via Sonogashira coupling of aryl iodides with （trimethylsilyl）acetylene catalyzed by MCM-41-supported mercapto palladium（0） complex, followed by desilylation under mild conditions. This polymeric palladium catalyst can be reused many times without any decrease in activity.     

The first heterogeneous Sonogashira coupling reaction of aryl halides with terminal alkynes catalyzed by diatomite‐supported palladium(II) salophen complex

We report here our observation that, using appropriate reaction conditions, the Sonogashira reaction can be performed without the need for copper catalyst and solvent. Our approach involves the use of diatomite‐supported palladium(II) salophen complex as a catalyst and triethylamine as a base. The methodology works, to differing extents, for aryl iodides and bromides. This heterogeneous catalyst can be reused at least five times without any decrease in activity. Copyright © 2011 John Wiley & Sons, Ltd.     

Copper‐ and phosphine‐free Sonogashira coupling reaction catalyzed by silica–(acac)‐supported palladium nanoparticles in water

A palladium‐based catalyst supported on acac‐functionalized silica was used as a heterogeneous catalyst for the Sonogashira cross‐coupling reaction of various aryl halides and phenylacetylene under copper‐ and phosphine‐free conditions. This catalytic system serves as an efficient and stable catalyst for this cross‐coupling reaction and allows easy separation and recycling of the catalyst. The catalyst could be recycled for five runs without appreciable loss of its catalytic activity. In addition, the reaction was carried out in water as a green solvent. Copyright © 2014 John Wiley & Sons, Ltd.     

New insight in the O2 activation by nano Fe/Cu bimetals: The synergistic role of Cu(0) and Fe(II)

This study demonstrated that as-synthesized nano Fe/Cu bimetals could achieve significant enhancement in the degradation of diclofenac (DCF), as compared to much slow removal of DCF by Cu(II) or zero valent iron nanoparticles (nZVI), respectively. Further observations on the evolution of O₂ activation process by nano Fe/Cu bimetals was conducted stretching to the preparation phase (started by nZVI/Cu²⁺). Interesting breakpoints were observed with obvious sudden increase in the DCF degradation efficiency and decrease in solution pH, as the original nZVI just consumed up to Fe(II) and Cu(II) appeared again. It suggested that the four-electrons reaction of O₂ and Cu-deposited nZVI would occur to generate water prior to the breakpoints, while Cu(0) and Fe(II) would play most important role in activation of O₂ afterwards. Through the electron spin resonance (ESR) analysis and quenching experiments, OH was identified as the responsible reactive species. Further time-dependent quantifications in the cases of Cu(0)/Fe(II) systems were carried out. It was found that the OH accumulation was positively and linearly correlated with nCu dose, Fe(II) consumption, and Fe(II) dose, respectively. Since either Cu(0) or Fe(II) would be inefficient in activating oxygen to produce OH, a stage-evolution mechanism of O₂ activated by nano Fe/Cu bimetals was proposed involving: (a) Rapid consumption of Fe(0) and release of Fe(II) based on the Cu-Fe galvanic corrosion, (b) adsorption and transformation of O₂ to O₂²⁻ at the nCu surface, and (c) Fe(II)-catalyzed activation of the adsorbed O₂²⁻ to OH.     

A beta-keto ester as a novel, efficient, and versatile ligand for copper(I)-catalyzed C-N, C-O, and C-S coupling reactions

Employing ethyl 2-oxocyclohexanecarboxylate as a novel, efficient, and versatile ligand, the copper-catalyzed coupling reactions of various N/O/S nucleophilic reagents with aryl halides could be successfully carried out under mild conditions. A variety of products including N-arylamides, N-arylimidazoles, aryl ethers, and aryl thioethers were synthesized in good to excellent yields.     

ONO pincer palladium (II) complexes featuring furoylhydrazone ligands: Synthesis,characterization and catalytic activity towards Suzuki–Miyaura coupling reaction

Four new palladium pincer complexes incorporating ONO type furoylhydrazone ligands have been prepared in good yields. These palladium complexes were structurally characterized by elemental analysis, infrared, ¹H‐ and ¹³C‐NMR spectra. X‐ray single crystal analyses of Pd1–Pd4 revealed that the metal center adopted a slightly distorted square planar geometry in which the hydrazone bound the metal ion via the phenolic‐O, azomethine‐N and imidolate‐O atoms. Using these ONO pincer complexes as catalyst, excellent yields of biaryls could be obtained for coupling of arylboronic acids with aryl bromides at a low catalyst loading (0.01 mol%).     

Vinylation of aryl iodides catalyzed byMCM-41supported poly-g-mercaptopropylsiloxanePd(0,II)complexes

Summary MCM-41-supported poly-γ-mercaptopropylsiloxane palladium (0,II) complexes were easily prepared from poly-γ-mercaptopropylsiloxane and MCM-41 in chloroform, followed by coordination to palladium chloride in ethane at room temperature. These catalysts are highly active and stereoselective for vinylation of aryl iodides with olefins, and give a variety of trans substituted products in high yields at 70^oC, and can be reused without loss in activity.</o:p>     

Polymer-supported palladium perfluorooctanesulfonate [Pd(OPf)2]: A recyclable and ligand-free palladium catalyst for copper-free Sonogashira coupling reaction in water under aerobic conditions

Amberlyst A-21, a kind of well-known and cheap polymeric material, was treated with palladium perfluorooctanesulfonate [Pd(OPf)₂] giving a reagent with a palladium loading of 1.94 (wt%). The polymer-supported fluorous palladium catalyzes the highly efficient Sonogashira coupling reaction in water. The reactions can be performed under copper- and ligand-free conditions in an air atmosphere. The palladium catalyst is easily separated and can be reused several times without a significant loss of catalytic activity.     

The first MCM-41-supported thioether palladium(0) complex: A highly active and stereoselective catalyst for Heck arylation of olefins with aryl halides

The first MCM-41-supported thioether palladium(0) complex has been synthesized from 3-(2-cyanoethylsulfanyl)propyltriethoxysilane via immobilization on MCM-41, followed by reacting with palladium chloride, and then the reduction with hydrazine hydrate. It was found that this complex has not only high activity and stereoselectivity for arylation reaction of conjugated alkenes with aryl iodides or activated aryl bromides, but also can efficiently catalyze the arylation reaction of conjugated alkenes with unactivated bromoarenes. This polymeric palladium catalyst can be easily recovered from the products and reused at least 10 times without loss of activity.     

Silica supported ammonium dihydrogen phosphate (NH4H2PO4/SiO2):A mild,reusable and highly efficient heterogeneous catalyst for the synthesis of 14-aryl-14-H-dibenzo[a,j]xanthenes

Silica supported ammonium dihydrogen phosphate (NH₄H₂PO₄/SiO₂) is found to be a recyclable heterogeneous catalyst for a rapid and efficient synthesis of various aryl-14-H-dibenzo[a,j]xanthenes with excellent yields under solvent-free conditions. The present methodology offers several advantages such as excellent yields, simple procedure, short reaction times and milder conditions.