Carboxymethylcellulose‐supported palladium nanoparticles generated in situ from palladium(II) carboxymethylcellulose as an efficient and reusable catalyst for ligand‐ and base‐free Heck–Matsuda and Suzuki–Miyaura couplings

A novel palladium(II) carboxymethylcellulose (CMC‐Pd^II) was prepared by direct metathesis from sodium carboxymethylcellulose and PdCl₂ in aqueous solution. Its catalytic activities were explored for Heck–Matsuda reactions of aryldiazonium tetrafluoroborate with olefins, and Suzuki–Miyaura couplings of aryldiazonium tetrafluoroborate with arylboronic acid. Both reactions proceeded at room temperature in water or aqueous ethanol media without the presence of any ligand or base, to provide the corresponding cross‐coupling products in good to excellent yields under atmospheric conditions. The CMC‐Pd^II and carboxymethylcellulose‐supported palladium nanoparticles (CMC‐Pd⁰) formed in situ in the reactions were characterized using Fourier transform infrared spectroscopy, X‐ray diffraction, inductively coupled plasma atomic emission spectrometry, and scanning and transmission electron microscopies. The homogeneous nature of the CMC‐Pd⁰ catalyst was confirmed via Hg(0) and CS₂ poisoning tests. Moreover, the CMC‐Pd⁰ catalyst could be conveniently recovered by simple filtration and reused for at least ten cycles in Suzuki–Miyaura reactions without apparently losing its catalytic activity. The catalytic system not only overcomes the basic drawbacks of homogeneous catalyst recovery and reuse but also avoids the need to fabricate palladium nanoparticles in advance. Copyright © 2015 John Wiley & Sons, Ltd.     

Suzuki–Miyaura coupling reaction in water in the presence of robust palladium immobilized on modified magnetic Fe3O4 nanoparticles as a recoverable catalyst

Aryl halides and especially inactive aryl chlorides were coupled to benzenoid aromatic rings in a Suzuki–Miyaura coupling reaction in the absence of organic solvents and toxic phosphine ligands. The reaction was catalysed by a recoverable magnetic nanocatalyst, Pd@Fe₃O₄, in aqueous media. This method is green, and the catalyst is easily removed from the reaction media using an external magnetic field and can be re‐used at least 10 times without any considerable loss in its activity. The catalyst was characterized using scanning and transmission electron microscopies, thermogravimetric analysis, inductively coupled plasma spectroscopy, Fourier transform infrared spectroscopy, CHN analysis, X‐ray diffraction and vibrating sample magnetometry.     

Mizoroki–Heck and Suzuki–Miyaura reactions mediated by poly(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid)‐stabilized magnetically separable palladium catalyst

The purpose of this work was to synthesize and characterize a new magnetic polymer nanosphere‐supported palladium(II) acetate catalyst for reactions requiring harsh conditions. In this regard, an air‐stable, moisture‐stable and highly efficient heterogenized palladium was synthesized by the coordination of palladium(II) acetate with poly(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid)‐grafted modified magnetic nanoparticles with a core–shell structure. The structure of the newly developed catalyst was characterized using various techniques. The catalytic activity of the resultant nano‐organometallic catalyst was evaluated in Mizoroki–Heck and Suzuki–Miyaura reactions to afford the corresponding coupling products in good to excellent yields. High selectivity as well as outstanding turnover number (14 143, 4900) and turnover frequency (28 296, 7424) values were recorded for the catalyst in Suzuki–Miyaura and Mizoroki–Heck reactions, respectively. Magnetic separation and recycling of the catalyst for at least six runs became possible without any significant loss of efficiency or any detectable palladium leaching.     

Nanopalladium on polyethylenimine–grafted starch: An efficient and ecofriendly heterogeneous catalyst for Suzuki–Miyaura coupling and transfer hydrogenation reactions

Functionalized natural polysaccharides are attractive supports for colloidal metal nanocatalysts due to their abundance, cheapness, biocompatibility and biodegradability. In this study, isocyanate–functionalized starch was prepared by treating with diisocyanate. Polyethylenimine grafted onto starch via the formation of urea linker. The palladium nanoparticles deposited starch PEIS@Pd(0) was obtained through a chelating–in situ reduction procedure. Characterization of these materials was done using Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X–ray diffraction, and inductive coupled plasma atomic emission spectrometry. The catalytic activity of PEIS@Pd(0) was then tested in two series of model reactions: Suzuki–Miyaura coupling and transfer hydrogenation. The catalyst could be recovered by simple filtration and was reused for five times without significant loss of catalytic activity, which confirmed the good stability of the catalyst.     

Amidophosphine‐stabilized palladium complexes catalyse Suzuki–Miyaura cross‐couplings in aqueous media

We report a simple and efficient procedure for Suzuki–Miyaura reactions in aqueous media catalysed by amidophosphine‐stabilized palladium complexes trans‐{L³PPh₂}₂PdCl₂ ( 3 ), trans‐{L³PPhtBu}₂PdCl₂ ( 4 ), [Pd(η³‐C₃H₅)(L³PPh₂)Cl] ( 5 ) and {Pd[2‐(Me₂NCH₂)C₆H₄](L³PPh₂)Cl} ( 6 ). The acidity of the NH proton in complexes 3 , 4 , 5 , 6 plays an important role in their catalytic activity. In addition, the palladium complexes cis‐{L¹PPh₂}PdCl₂ ( 1 ) and trans‐{L²PPh₂}₂PdCl₂ ( 2 ) stabilized by phosphines containing Y,C,Y‐chelating ligands L^1,2 have also been found to be useful catalysts for Suzuki–Miyaura reactions in aqueous media. The method can be effectively applied to both activated and deactivated aryl bromides yielding high or moderate conversions. The catalytic activity of couplings performed in pure water increases when utilizing a Pd complex with more acidic NH protons. A decrease of palladium concentration from 1.0 to 0.5 mol% does not lead to a substantial loss of conversion. In addition, Pd complex 1 can be efficiently recovered using two‐phase system extraction. Copyright © 2016 John Wiley & Sons, Ltd.     

Heck and Suzuki–Miyaura couplings catalyzed by nanosized palladium in polyaniline

A novel route to prepare polyaniline (PANI)‐supported Pd(0) nanoparticles by a one‐pot chemical route is presented. Nanosized Pd(0) particles were first prepared by reduction of Pd(OAc)₂ using t‐BuONa activated sodium hydride in refluxing THF. A ligand exchange with aniline on t‐BuONa‐stabilized Pd(0) particles yielded aniline‐stabilized particles. Pd(0)/PANI nanocomposites were finally obtained by polymerizing aniline‐stabilized Pd(0) particles using ammonium persulfate. Nanocomposites were characterized by transmission electron microscopy, X‐ray diffraction and X‐ray photoelectron spectroscopy. Results show that this one‐pot experimental route is successful in producing hybrid materials constituted of Pd(0) nanoparticles stabilized by PANI due to the strong binding of PANI amine groups to Pd(0) particles. TEM images of the nanohybrids show that metal particles with diameters of ca. 4.9 nm are homogeneously dispersed in PANI. The preliminary results indicate that the Pd(0) particles supported on PANI behave as efficient heterogeneous catalysts in the Heck and Suzuki–Miyaura reactions of aryl iodides. Copyright © 2005 John Wiley & Sons, Ltd.     

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.     

Synthesis of a palladium complex bearing 2‐phenylbenzothiazole and its application to Suzuki–Miyaura coupling reaction

The palladacycle complex [L^sPdOAc]₂ bearing 2‐phenyl benzothiazole was synthesized and characterized by NMR and X‐ray crystallography. [L^sPdOAc]₂ was used as a catalyst in the Suzuki–Miyaura cross coupling reaction of 4‐bromotoluene with phenylboronic acid, which resulted in a conversion of >90% with 5 mol% of the Pd complex within 10 min at 60°C.     

Palladium nanoparticles deposited on a graphene–benzimidazole support as an efficient and recyclable catalyst for aqueous‐phase Suzuki–Miyaura coupling reaction

Graphene oxide was functionalized with benzimidazole for palladium immobilization. The resultant graphene–benzimidazole‐supported palladium composite (G‐BI‐Pd) was characterized using infrared and Raman spectroscopies, transmission electron microscopy and energy‐dispersive X‐ray spectroscopy. G‐BI‐Pd showed excellent catalytic activity and fast reaction kinetics in the aqueous‐phase Suzuki–Miyaura reaction of aryl iodides and bromides with phenylboronic acid under relatively mild conditions (5–25 min, 80 °C). The catalyst can be used several times without any significant loss of its catalytic activity.     

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.     

Porphyrin‐based polymer‐supported palladium as an excellent and recyclable catalyst for Suzuki–Miyaura coupling reaction in water

A porphyrin‐based polymer with high surface area was synthesized using 5,10,15,20‐tetraphenylporphyrin through a one‐pot Friedel–Crafts alkylation reaction. Pd(II) was successfully supported on this polymer. This strategy provides an easy approach to produce highly stable Pd–porphyrin‐based polymer. The resulting Pd catalyst was characterized using Fourier transform infrared and X‐ray photoelectron spectroscopies, thermogravimetric analysis, scanning and transmission electron microscopies and N₂ adsorption–desorption measurements. This porphyrin‐based polymer‐supported Pd was used as a heterogeneous catalyst for Suzuki–Miyaura coupling reaction in water. The results demonstrated that this Pd catalyst indeed exhibited excellent catalytic activity and recycling performance in water, even for inactive aryl chloride substrate. A new heterogeneous strategy for catalyzing the Suzuki–Miyaura reaction in water is provided.     

A green synthesis of palladium nanoparticles by Sapindus mukorossi seed extract and use in efficient room temperature Suzuki–Miyaura cross‐coupling reaction

A simple and green method for the synthesis of palladium nanoparticles using an aqueous extract of Sapindus mukorossi seed has been demonstrated. The synthesized nanoparticles were characterized using UV–visible spectroscopy, powxder X‐ray diffraction, energy‐dispersive X‐ray analysis and transmission electron microscopy. The nanocatalyst was successfully utilized in an efficient Suzuki–Miyaura cross‐coupling reaction at room temperature.     

Pd(l‐proline)2 complex: an efficient catalyst for Suzuki–Miyaura coupling reaction in neat water

An efficient catalytic system for Suzuki–Miyaura coupling reactions in neat water has been developed by using a water‐soluble Pd(l ‐proline)₂ catalyst. Under the optimized conditions, various biaryl compounds were obtained in good to excellent yields and a wide range of functional groups on the tested substrates were well tolerated. The catalytic system could be reused at least six times with no significant loss in its activity. Copyright © 2014 John Wiley & Sons, Ltd.     

Highly efficient polymer‐stabilized palladium heterogeneous catalyst: Synthesis,characterization and application for Suzuki–Miyaura and Mizoroki–Heck coupling reactions

A suitable approach to stabilize palladium nanoparticles (Pd NPs), with an average diameter of 3–4 nm, on magnetic polymer is described. A new magnetic polymer containing 4′‐(4‐hydroxyphenyl)‐2,2′:6′,2″‐terpyridine (HPTPy) ligand was prepared by the polymerization of itaconic acid (ITC) as a monomer and trimethylolpropane triacrylate (TMPTA) as a cross‐linker and fully characterized. Pd NPs embedded on the magnetic polymer were successfully applied in Suzuki–Miyaura and Mizoroki–Heck coupling reactions under low palladium loading conditions, and provided the corresponding products with excellent yields (up to 98%) and high catalytic activities (TOF up to 257 hr^?1). Also, the catalyst can be easily separated and reused for at least consecutive five times with a small drop in catalytic activity.     

Synthesis of dendrimers terminated by DABCO ligands and applications of its palladium nanoparticles for catalyzing Suzuki–Miyaura and Mizoroki–Heck couplings

A new kind of silica‐supported third‐generation dendrimers capped by 1,4‐diaza‐bicyclo[2.2.2]octane (DABCO) group‐stabilized palladium(0) nanoparticles, and their enhanced catalytic activity in Suzuki–Miyaura and Mizoroki–Heck reactions in excellent yield under mild conditions, was reported. The resulting silica‐supported dendrimer‐stabilized palladium(0) nanoparticles with a particle size of 10–20 nm were prepared in situ by treatment with PdCl₂ and hydrazine in ethanol at 60 °C for 24 h. The catalyst as prepared was characterized by FT‐IR, X‐ray diffraction, thermal analysis, elementary analysis (EA), scanning electron microscopy and transmission electron microscopy. Recycling experiments showed that the catalyst could be easily recovered by simple filtration and reused for up to five cycles without losing its activity. Copyright © 2012 John Wiley & Sons, Ltd.     

Tetraphosphine/palladium‐catalyzed Suzuki–Miyaura coupling of heteroaryl halides with 3‐pyridine‐ and 3‐thiopheneboronic acid: an efficient catalyst for the formation of biheteroaryls

An easily prepared tetraphosphine N,N,N′,N′‐tetra(diphenylphosphinomethyl)‐1,2‐ethylenediamine (L1) associated with [Pd(η³‐C₃H₅)Cl]₂ affords an efficient catalyst for Suzuki–Miyaura coupling of 3‐pyridineboronic acid with heteroaryl bromides. Reaction could be performed with as little as 0.02 mol% catalyst and a high turnover number of 2500 is obtained. A wide range of substrates is investigated with satisfactory yields, and good compatibility with aminogroup‐substituted pyridines and unprotected indole is exhibited. This protocol can also be applied successfully to the reaction of heteroaryl bromides with 3‐thiopheneboronic acid. This Pd‐tetraphosphine catalyst efficiently restrains the poisoning effect from heteroaryls, and shows good stability and longevity. Copyright © 2013 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.     

Palladium complex containing two sterically hindered ligands as highly efficient catalyst for Suzuki–Miyaura reaction

A new palladium(II) complex containing two sterically hindered ligands, a P,P‐bonded diphosphine and N,N‐bonded Schiff base, within the same coordination sphere has been synthesized and investigated as a catalyst for the Suzuki–Miyaura cross‐coupling reactions of aryl halides with arylboronic acids. The reaction was highly efficient with aryl bromides in water at room temperature and aryl chlorides in dimethylformamide under relatively mild conditions. Excellent yields of coupling products were obtained for a wide range of aryl halides including heteroaryl halides with a low loading of catalyst. Copyright © 2015 John Wiley & Sons, Ltd.     

Novel palladium nanoparticles supported on β‐cyclodextrin@graphene oxide as magnetically recyclable catalyst for Suzuki–Miyaura cross‐coupling reaction with two different approaches in bio‐based solvents

A novel nanocatalyst was designed and prepared. Initially, the surface of magnetic graphene oxide (M‐GO) was modified using thionyl chloride, tris(hydroxymethyl)aminomethane and acryloyl chloride as linkers which provide reactive C═C bonds for the polymerization of vinylic monomers. Separately, β‐cyclodextrin (β‐CD) was treated with acryloyl chloride to provide a modified β‐CD. Then, in the presence methylenebisacrylamide as a cross‐linker, monomers of modified β‐CD and acrylamide were polymerized on the surface of the pre‐prepared M‐GO. Finally, palladium acetate and sodium borohydride were added to this composite to afford supported palladium nanoparticles. This fabricated nanocomposite was fully characterized using various techniques. The efficiency of this easily separable and reusable heterogeneous catalyst was successfully examined in Suzuki–Miyaura cross‐coupling reactions of aryl halides and boronic acid as well as in modified Suzuki–Miyaura cross‐coupling reactions of N‐acylsuccinimides and boronic acid in green media. The results showed that the nanocatalyst was efficient in coupling reactions for direct formation of the corresponding biphenyl as well as benzophenone derivatives in green media based on bio‐based solvents. In addition, the nanocatalyst was easily separable, using an external magnet, and could be reused several times without significant loss of activity under the optimum reaction conditions.