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%).     

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.     

Biguanidine‐functionalized chitosan to immobilize palladium nanoparticles as a novel,efficient and recyclable heterogeneous nanocatalyst for Suzuki–Miyaura coupling reactions

Biguanidine‐functionalized chitosan was synthesized and combined with palladium nanoparticles to yield a recyclable, environmentally benign, heterogeneous catalytic system for the Suzuki–Miyaura C–C coupling reaction. The catalyst was characterized using various techniques. The catalyst was used in Suzuki cross‐coupling reactions of various aryl halides, including less reactive chlorobenzenes, with phenylboronic acid to give biaryls without any additive or ligand. A reusability test demonstrated that the catalyst was highly efficient even after six runs. Solid‐phase poisoning and leaching tests indicated that the catalyst has a heterogeneous nature. Copyright © 2016 John Wiley & Sons, Ltd.     

Palladium supported on silica–chitosan hybrid material (Pd‐CS@SiO2) for Suzuki–Miyaura and Mizoroki–Heck cross‐coupling reactions

Palladium supported on silica–chitosan hybrid material was prepared and characterized using thermogravimetric and differential thermogravimetric analyses, scanning electron microscopy, and Fourier transform infrared, energy‐dispersive X‐ray and X‐ray photoelectron spectroscopies. The prepared Pd‐CS@SiO₂ catalyst (1 mol%) was used for the Suzuki–Miyaura cross‐coupling reaction of various aryl halides and arylboronic acids in 95% ethanol at 80 °C and the Mizoroki–Heck reaction in dimethylformamide at 110 °C using K₂CO₃ as a base. The developed catalyst is well suitable for the 3R approach (recoverable, robust, recyclable) for cross‐coupling reactions without appreciable loss of its activity. Copyright © 2015 John Wiley & Sons, Ltd.     

Pd nanoparticles immobilized on PNIPAM–halloysite: highly active and reusable catalyst for Suzuki–Miyaura coupling reactions in water

Poly(N‐isopropylacrylamide)–halloysite (PNIPAM‐HNT) nanocomposites exhibited inverse temperature solubility with a lower critical solution temperature (LCST) in water. Palladium (Pd) nanoparticles were anchored on PNIPAM‐HNT nanocomposites with various amounts of HNT from 5 to 30 wt%. These Pd catalysts exhibited excellent reactivities for Suzuki–Miyaura coupling reactions at 50–70 °C in water. In particular, Pd anchored PNIPAM/HNT (95:5 w/w ratio) nanocomposites showed excellent recyclability up to 10 times in 96% average yield by simple filtration. 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.     

A highly efficient heterogeneous montmorillonite K‐10‐supported palladium catalyst for Suzuki–Miyaura cross‐coupling reaction in aqueous medium

A heterogeneous montmorillonite K‐10‐supported palladium triphenylphosphine catalyst is reported for the Suzuki–Miyaura cross‐coupling reaction at room temperature. A library of electronically diverse aryl bromides and arylboronic acids underwent the cross‐coupling reaction at very good rates in aqueous solvent. The reusability of the catalyst was also examined and it was found to be effective up to three catalytic cycles. Copyright © 2014 John Wiley & Sons, Ltd.     

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.     

Synthesis of chitosan derivatives supported palladium complexes and their catalytic behavior in the Heck reaction

Two kinds of chitosan derivatives, crosslinked chitosan and crosslinked chitosan condense with salilylaldehyde, supported palladium complexes (CL‐CTS‐Pd and CL‐S‐CTS‐Pd) were synthesized and characterized by X‐ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), differential thermal analysis (DTA), etc. These complexes are efficient catalysts for the Heck reaction under atmospheric conditions and can be easily recovered and reused. The detailed studies show that the catalyst CL‐S‐CTS‐Pd is much more efficient than CL‐CTS‐Pd under the same conditions. CL‐S‐CTS‐Pd keeps its catalytic activity in the Heck reaction of acrylic acid with iodobenzene even at a low temperature (60°C) or with tiny amounts of the catalyst (0.05 mol%Pd). Yields of making cinnamic acid were even as high as 75.3% in the Heck reaction of acrylic acid with iodobenzene using CL‐S‐CTS‐Pd that was recovered 10 times. Copyright © 2005 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.     

Synthesis of 4‐substituted styrene compounds via palladium catalyzed Suzuki–Miyaura reaction using bidentate Schiff base ligands

Air‐stable symmetric Schiff base have been synthesized and proved to be efficient ligands for Suzuki–Miyaura reaction between aryl bromides and arylboronic acids using PdCl₂(CH₃CN)₂ as palladium source under aerobic conditions. The coupling reaction proceeded smoothly using N,N‐bis(anthracen‐9‐ylmethylene)benzene‐1,2‐diamine (L₇) as ligand to provide 4‐substituted styrene compounds in good yields. Copyright © 2009 John Wiley & Sons, Ltd.     

Greener approach for synthesis of monodispersed palladium nanoparticles using aqueous extract of green tea and their catalytic activity for the Suzuki–Miyaura coupling reaction and the reduction of nitroarenes

A facile and green route for the synthesis of palladium nanoparticles (NPs) was developed utilizing non‐toxic and renewable natural green tea extract as the reducing, stabilizing and capping agent. The as‐prepared Pd‐NPs@G.Tea extract was characterized using UV–visible spectroscopy, X‐ray diffraction, Fourier transform infrared spectroscopy, field‐emission scanning electron microscopy, transmission electron microscopy and energy‐dispersive X‐ray spectroscopy. The Pd‐NPs@G.Tea extract could be used as an efficient and heterogeneous catalyst for Suzuki coupling reactions between phenylboronic acid and a range of aryl halides containing iodo, bromo and chloro moieties, and also for the reduction of nitroarenes using sodium borohydride in an environmentally friendly medium. Excellent yields of products were obtained with a wide range of substrates and the catalyst was recycled multiple times without any significant loss of its catalytic activity.     

A highly active palladium(II)–bis(oxazoline) catalyst for Suzuki–Miyaura,Mizoroki–Heck and sonogashira coupling reactions in aqueous dimethylformamide

An efficient catalytic system based on a new palladium–bis(oxazoline) ( Pd-BOX-1 ) complex has been developed. The complex Pd-BOX-1 adopts a legless chair‐type structure where the distorted square planar [PdN₂Cl₂] moiety and the benzene ring spacer represent the seat and the chair back, respectively. The catalytic activity of Pd-BOX-1 has been investigated in dimethylformamide–water under aerobic and mild conditions in Suzuki–Miyaura coupling reactions of arylboronic acids with aryl iodides, aryl bromides and aryl chlorides, Mizoroki–Heck coupling reactions of aryl halides with styrene derivatives, and Sonogashira coupling reactions of aryl halides with terminal alkynes. A wide range of functional groups as substituents on the arylboronic acids and aryl halides were considered. Pd-BOX-1 demonstrates exceptional air and moisture stability. Of note, the catalyst system based on Pd-BOX-1 shows high recycling ability in Suzuki–Miyaura coupling reactions in dimethylformamide–water without any loss in catalytic activity. Copyright © 2015 John Wiley & Sons, Ltd.     

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.     

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.     

Green synthesis of palladium nanoparticles using Pistacia atlantica kurdica gum and their catalytic performance in Mizoroki–Heck and Suzuki–Miyaura coupling reactions in aqueous solutions

A one‐pot green method for the synthesis of palladium nanoparticles (Pd‐NPs) supported on Pistacia atlantica kurdica (P. a. kurdica) gum is described. This natural gum is used as a reducing and stabilising agent. The formation of the Pd‐NPs/P. a. kurdica gum catalyst was verified using several techniques, such as Fourier transform infrared spectroscopy, ultraviolet–visible spectrophotometry, scanning and transmission electron microscopies, X‐ray diffraction, energy‐dispersive X‐ray spectroscopy, dynamic light scattering and wavelength‐dispersive X‐ray spectroscopy. The Pd‐NPs stabilised by P. a. kurdica gum were employed as a heterogeneous catalyst in Mizoroki–Heck and Suzuki–Miyaura cross‐coupling reactions at low palladium loading (0.1 mol%) under aerobic, phosphine‐free and ligand‐free conditions in water. Product yields of up to 98%, a facile work‐up, no evidence of leached palladium from the catalyst surface and smooth recovery of the catalyst, which can be reused at least eight times, confirm the efficiency of the catalysts in the reactions investigated. Copyright © 2015 John Wiley & Sons, Ltd.     

Bis(imino)pyridine palladium(II) complexes as efficient catalysts for the Suzuki–Miyaura reaction in water

Bis(imino)pyridine palladium(II) complexes 3 and 4 of type [PdCl(L)PF₆] are found to be efficient catalysts for Suzuki–Miyaura reactions of aryl halides and arylboronic acids. The reactions proceed smoothly to generate the corresponding biaryl compounds in moderate to excellent yields. The synthesis of various fluorinated biphenyl derivatives was successfully achieved by the complex 4 catalyzed the Suzuki–Miyaura reaction in the presence of surfactants bearing a long alkyl chain. Copyright © 2009 John Wiley & Sons, Ltd.     

Magnetic apple seed starch functionalized with 2,2′‐furil as a green host for cobalt nanoparticles: Highly active and reusable catalyst for Mizoroki–Heck and the Suzuki–Miyaura reactions

From the perspective of green chemistry, in catalytic systems, being low cost and eco‐friendly, in addition to high chemical and thermal stability, are requirements of support materials. In this regard, we used apple seed starch as an accessible, nontoxic, and cost‐effective support material. In order to take advantage of magnetic separation, the magnetite nanoparticles were chosen as an ideal pair for apple seed starch. Furthermore, during the Schiff base reaction, the magnetic apple seed starch was functionalized with 2,2′‐furil along with amine functionality to be used as a bio‐support for immobilization of cobalt. The introduction of cobalt had a significant effect on the greenness of the catalyst and reducing its price. FT‐IR, TGA, XRD, FE‐SEM, TEM, VSM, ninhydrin test, element mapping, AAS, and EDX analysis were applied to characterize the newly prepared catalyst. The effectiveness of this novel Schiff base supported catalyst was evaluated in the Mizoroki–Heck and the Suzuki–Miyaura coupling reactions. High reactivity and selectivity were among the most prominent characteristics of the catalyst as compared to previously reported catalysts. The longevity test and hot filtration showed the ability to use the catalyst at least 5 times and negligible cobalt leaching during the reaction, respectively. This work is the first report on the usage of apple seed starch as a supporting catalyst and 2,2′‐furil as a ligand in the catalyst modifications and catalytic activity. Accordingly, this can be the beginning of an attractive way in the design and synthesis of heterogeneous catalysts.     

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.     

Synthesis,characterization and catalytic activity of Pd(II) complexes with N‐allyl functionalized imidazol‐2‐ylidenes in Suzuki–Miyaura reaction

A series of Pd–N‐heterocyclic carbene (Pd–NHC) complexes were synthesized and characterized by elemental analysis and spectroscopic methods. In addition, the molecular structures of 3c and 4c were determined by X‐ray diffraction studies. Finally, the performance of complexes 3 and 5 were studied on Suzuki–Miyaura reactions of phenylboronic acid with aryl bromides. Copyright © 2014 John Wiley & Sons, Ltd.