Pd/MOF‐199: As an efficient heterogeneous catalyst for the Suzukie Miyaura cross‐coupling reaction

Successful deposition of Pd nanoparticles is described using MOF‐199 as a support. Various characterization techniques including FTIR, XRD, SEM, BET‐BJH, TG‐DTA, and NH₃‐TPD were used to verify the efficiency of catalysts. Pd/MOF‐199 is utilized as a catalyst for Suzukie Miyaura reactions with reasonable to excellent reaction yields under reflux conditions in H₂O: ethanol solvent.     

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.     

Terephthalic acid derived ligand‐stabilized palladium nanocomposite catalyst for Heck coupling reaction: without surface‐modified heterogeneous catalyst

A new protocol is reported for the synthesis of a heterogeneous palladium nanocomposite stabilized with a terephthalic acid‐derived ligand (N ,N ‐bis(4‐hydroxy‐3‐methoxybenzylidene)terephthalohydrazide). This is a highly insoluble ligand in common organic solvents, except dimethylformamide and dimethylsulfoxide. The resulting palladium nanocomposite acts as an efficient catalyst precursor for Mizoroki–Heck coupling reactions conducted under various reaction conditions. The spectral data suggest that the rate, yield and recycling of the catalyst are more effective for C–C coupling reactions. Copyright © 2016 John Wiley & Sons, Ltd.     

Alumina‐supported nickel catalyst for liquid‐phase reactions: an expedient and efficient heterogeneous catalyst for hydrogenation reactions

The preparation of a new nickel(0)/Al₂O₃ catalyst for hydrogenation reactions is described. The nickel(0)/Al₂O₃ catalysts were prepared by impregnation of alumina with a solution of a nickel(II) salt. After drying, the nickel(II) salt was reduced under mild conditions into nickel(0) using t‐BuONa‐activated sodium hydride in tetrahydrofuran at 65 °C. The nickel(0)/Al₂O₃ catalysts obtained were characterized by transmission electron microscopy and energy‐dispersive X‐ray spectroscopy. The supported catalysts were successfully used in solution‐phase hydrogenation of double and triple bonds. Although the activity of the nickel(0)/Al₂O₃ is comparable to non‐supported nickel(0) reagents, it has the advantage of being reusable more than ten times with only a slight decrease of reactivity. Copyright © 2003 John Wiley & Sons, Ltd.     

Green synthesis of Cu/zirconium silicate nanocomposite by using Rubia tinctorum leaf extract and its application in the preparation of N‐benzyl‐N‐arylcyanamides

A simple and convenient protocol was established for the synthesis of the N‐benzyl‐N‐arylcyanamides through N‐benzylation of a wide variety of arylcyanamides using copper nanoparticles immobilized on natural zirconium silicate as a novel and green heterogeneous catalyst. In this study, we showed a novel, cost efficient, convenient and simple method for green synthesis of Cu/zirconium silicate nanocomposite by using Rubia tinctorum leaf extract as capping and reducing agent. The structure of the novel catalyst was successfully characterized using a number of micro/spectroscopic techniques such as XRD, FESEM, BET, EDS, TEM, FT‐IR and elemental mapping. TEM micrographs of obtaining biocatalyst revealed mostly spherical particles with an average diameter of about 15–25 nm on the surface of natural support. The prepared catalyst was used in the N‐benzylation of a variety of arylcyanamides with benzyl bromide and showed high activity and stability for the efficient synthesis of N‐benzylarylcyanamides in good yields. Remarkably, the catalyst can be easily recovered from the reaction medium and reused up to five runs without losing its catalytic activity.     

Copper‐Catalyzed N‐Arylation of 1,1,3,3‐TetramethylguanidinePhenyl Isocyanate Adduct

The synthesis of a novel class of 3‐[bis(dimethylamino)methylidene]‐1,1‐diarylureas via a Cu‐catalyzed multicomponent reaction of phenyl isocyanate (PhNCO), 1,1,3,3‐tetramethylguanidine, and aryl halides is described.     

Buchwald‐Hartwig amination reaction of aryl halides using heterogeneous catalyst based on Pd nanoparticles decorated on chitosan functionalized graphene oxide

In this work, graphene oxide was functionalized with chitosan (GO‐Chit) followed by a simple approach for immobilization of palladium nanoparticles onto a chitosan grafted graphene oxide surface. The Pd‐nanocomposite (GO‐Chit‐Pd) was characterized using Transmission Electron Microscopy (TEM), Fourier transforms infrared spectroscopy (FT‐IR), and X‐ray diffraction (XRD) measurements. The catalytic activity of the prepared heterogeneous graphene oxide functionalized chitosan‐palladium (GO‐Chit‐Pd) was investigated in term of C‐N coupling reaction (Buchwald‐Hartwig amination reaction of aryl halides) yielding products of N‐arylamines. The easy purification, convenient operation, and environmental friendliness, combined with a high yield, render this method viable for use in both laboratory research and larger industrial scales. Studying the reusability of the catalyst in this work showed that it could be reused for five times without obvious loss in catalytic activity.     

Palladium nanoparticle‐decorated magnetic pomegranate peel‐derived porous carbon nanocomposite as an excellent catalyst for Suzuki–Miyaura and Sonogashira cross‐coupling reactions

Porous carbon (PC) material was prepared from the carbonization of pomegranate peel waste. Subsequently, magnetically separable Fe₃O₄@PC was synthesized from Fe₃O₄ nanoparticles decorated on PC by the co‐precipitation method of iron ions. Finally, Fe₃O₄@PC was successfully decorated with palladium nanoparticles in a simple route by reducing H₂PdCl₄ in the presence of sodium dodecylsulfate, which was used as both surfactant and reducing agent. Additionally, the effect of temperature on the carbonization process was studied. The Pd/Fe₃O₄@PC nanocomposite was used as an efficient and heterogeneous catalyst for Suzuki–Miyaura and Sonogashira cross‐coupling reactions in an environmentally friendly medium.     

New bis(N‐heterocyclic carbene) palladium complex immobilized on magnetic nanoparticles: as a magnetic reusable catalyst in Suzuki‐Miyaura cross coupling reaction

A new bis(N ‐heterocyclic carbene) (NHC) palladium complex supported on silica coated magnetic nanoparticles (MNPs) was prepared using the reaction of synthesized Pd‐NHC complex with MNPs. The Pd‐NHC complex was prepared using the reaction of a hydroxyl‐functionalized bis‐imidazolium ionic liquid. The Pd‐NHC organometallic complex was used as a heterogeneous recyclable and active catalyst in the Suzuki‐Miyaura reaction and various aryl halides were coupled with arylboronic acids in order to synthesize diverse biaryls in good to excellent yields. The prepared catalyst was characterized by use of some different microscopic and spectroscopic techniques including elemental analysis, FT‐IR spectroscopy, diffuse reflectance UV–Vis spectrophotometery, scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM) and X‐ray diffraction (XRD). The Pd‐NHC catalyst system is a magnetic reusable catalyst and it can be separated from the reaction mixture using an external magnetic field. The catalyst was reusable in the Suzuki‐Miyaura coupling reaction at least for 6 times without significant decreasing in its catalytic activity.     

Green chemical synthesis of Pd nanoparticles for use as efficient catalyst in Suzuki‐Miyaura cross‐coupling reaction

Herein, we report the synthesis of tiny spherical Pd nanoparticles (NPs) by green chemical method under ambient conditions using flower extract of Lantana camara plant. The size of the Pd NPs is tunable from 4.7 to 6.3 nm by systematically controlling the concentration of either metal ions or plant extract. The synthesized Pd NPs were well characterized by different spectroscopic, microscopic and diffractometric techniques. The Pd NPs offered good size‐dependent catalytic activity in the Suzuki‐Miyaura C‐C coupling reaction under mild reaction conditions in (1: 1) water‐ethanol mixture. The catalyst is stable and exhibited excellent reusability up to three cycles of coupling reaction after which the catalytic activity decreases.     

Threonine stabilizer‐controlled well‐dispersed small palladium nanoparticles on modified magnetic nanocatalyst for Heck cross‐coupling process in water

We report the synthesis of magnetically separable Fe₃O₄@Silica‐Threonine‐Pd⁰ magnetic nanoparticles with a core–shell structure. After synthesis of Fe₃O₄@Silica, threonine as an efficient stabilizer/ligand was bonded to the surface of Fe₃O₄@Silica. Then, palladium nanoparticles were generated on the threonine‐modified catalyst. The threonine stabilizer helps to generate palladium nanoparticles of small size (less than 4 nm) with high dispersity and uniformity. Magnetically separable Fe₃O₄@Silica‐Threonine‐Pd⁰ nanocatalyst was fully characterized using various techniques. This nanocatalyst efficiently catalysed the Heck cross‐coupling reaction of a variety of substrates in water medium as a green, safe and inexpensive solvent at 80°C. The Fe₃O₄@Silica‐Threonine‐Pd⁰ catalyst was used for at least eight successful consecutive runs with palladium leaching of only 0.05%.     

Palladium supported on modified magnetic nanoparticles: a phosphine‐free and heterogeneous catalyst for Suzuki and Stille reactions

An efficient magnetic nanoparticle‐supported palladium (Fe₃O₄/SiO₂‐PAP‐Pd) catalyst is reported for the Suzuki cross‐coupling and Stille reactions. This method provides a novel and much improved modification of the Suzuki and Stille coupling reactions in terms of phosphine‐free catalyst, short reaction time, clean reaction and small quantity of catalyst. Another important feature of this method is that the catalyst can be easily recovered from the reaction mixture and reused with no loss of its catalytic activity. Copyright © 2015 John Wiley & Sons, Ltd.     

Magnetite tethered mesoionic carbene‐palladium (II): An efficient and reusable nanomagnetic catalyst for Suzuki‐Miyaura and Mizoroki‐Heck cross‐coupling reactions in aqueous medium

In this paper, a highly active, air‐ and moisture‐stable and easily recoverable magnetic nanoparticles tethered mesoionic carbene palladium (II) complex (MNPs‐MIC‐Pd) as nanomagnetic catalyst was successfully synthesized by a simplistic multistep synthesis under aerobic conditions using commercially available inexpensive chemicals for the first time. The synthesized MNPs‐MIC‐Pd nanomagnetic catalyst was in‐depth characterized by numerous physicochemical techniques such as FT‐IR, ICP‐AES, FESEM, EDS, TEM, p‐XRD, XPS, TGA and BET surface area analysis. The prepared MNPs‐MIC‐Pd nanomagnetic catalyst was used to catalyze the Suzuki–Miyaura and Mizoroki–Heck cross‐coupling reactions and exhibited excellent catalytic activity for various substrates under mild reaction conditions. Moreover, MNPs‐MIC‐Pd nanomagnetic catalyst could be easily and rapidly recovered by applying an external magnet. The recovered MNPs‐MIC‐Pd nanomagnetic catalyst exhibited very good catalytic activity up to ten times in Suzuki–Miyaura and five times in Mizoroki–Heck cross‐coupling reactions without considerable loss of its catalytic activity. However, MNPs‐MIC‐Pd nanomagnetic catalyst shows notable advantages such as heterogeneous nature, efficient catalytic activity, mild reaction conditions, easy magnetic work up and recyclability.     

Ultra‐small and highly dispersed Pd nanoparticles inside the pores of ZIF‐8: Sustainable approach to waste‐minimized Mizoroki–Heck cross‐coupling reaction based on reusable heterogeneous catalyst

The rapid development of nanomaterials, particularly advanced hybrid nanoparticles, has made new opportunities for the design and fabrication of high‐performance metal‐based catalysts. However, generating metal nanoparticles of desired size without aggregation is an important challenge for enhancing the catalytic activity of metal nanoparticles supported in the host matrix. In this work, a hybrid nanoporous material, namely Pd nanoparticles@N‐heterocyclic carbene@ZIF‐8, with a high internal surface area was successfully prepared using a dispersed anionic sulfonated N‐heterocyclic carbene–Pd(II) precursor inside the cavities of zeolitic imidazolate framework (ZIF‐8) using an impregnation approach followed by reduction with NaBH₄. The anionic sulfonated N‐heterocyclic carbene was found to be a superb ligand for the stabilization of Pd nanoparticles in the pores of ZIF‐8. The resulting system was applied to the Mizoroki–Heck cross‐coupling reaction, in which the catalyst showed high catalytic activity under mild reaction conditions.     

A highly reactive and magnetic recyclable catalyst based on silver nanoparticles supported on ferrite for N‐monoalkylation of amines with alcohols

Fe₃O₄@SiO₂‐Ag catalyst was found to be highly active and selective in the N ‐alkylation of amines with a variety of aromatic and linear alcohols. The heterogeneous nature of the Fe₃O₄@SiO₂‐Ag catalyst allows easy recovery and regeneration by applying an external magnet for six subsequent reaction cycles. The prepared catalyst was characterized using electron microscopy techniques, X‐ray diffraction, vibrating sample magnetometry and atomic absorption spectroscopy.     

Ligandless heterogeneous palladium: an efficient and recyclable catalyst for Suzuki‐type cross‐coupling reaction

A mild and efficient ligand‐free Suzuki‐type cross‐coupling reaction of benzoyl chlorides and arylboronic acids catalyzed by heterogeneous Pd/C was developed. Benzoyl chlorides undergo cross‐coupling with electronically diverse arylboronic acids to give biaryl ketones in excellent yield, under aqueous media and optimum temperature. The application of 3 mol% of 10 wt% Pd/C to the cross‐coupling delivers utmost efficiency, and could be reused up to many consecutive cycles without any loss in activity. This method proceeds under aqueous media and a recyclable catalytic system, offering an environmentally benign alternative to the existing protocols. Copyright © 2014 John Wiley & Sons, Ltd.     

The palladium‐catalyzed C‐N cross‐coupling reaction of diheteroaryl disulfides with heterocyclic amines

The Pd‐catalyzed cross‐coupling reaction of 1, 2‐di(pyrimidin‐2‐yl) disulfides with heterocyclic amines including 2‐amino pyrimidines and 1,3,4‐thiadiazol‐2‐amines to deliver symmetrical C‐N coupling products in moderate to good yields is reported. This method provides an opportunity for synthesis of bioactive molecules and pharmaceutically interesting compounds containing heterocycle motifs. The reported protocol shows good functional group compatibility, and provides a new strategy for preparation of C2‐amination pyrimidine derivatives from heterocyclic disulfides.     

Octanuclear Cu(I)‐dithiophosphates: An Efficient Catalyst System for N‐Arylation of Azoles,Amines, and Amides

The formation of a C‐N bond via the cross‐couplings of aryl iodides with azoles, aryl amine, and amides can be successfully achieved in decent yield by the utilization of both [Cu ₈(H){S₂P(OⁱPr)₂}₆]⁺ and [Cu₈{S₂P(OEt)₂}₆]²⁺ as the pre‐catalysts.     

Sulfonated palladium(II) N‐heterocyclic carbene complex immobilized on nano–micro size poly(4‐vinylpyridinium chloride) for Suzuki‐Miyaura cross‐coupling reaction

The sulfonated palladium(II) N‐heterocyclic carbene complex Pd^II(NHC)SO₃^?, supported on poly(4‐vinylpyridinium chloride), was used as a heterogeneous, recyclable and active catalyst for the Suzuki–Miyaura reaction. This catalyst was applied for coupling of various aryl halides with phenylboronic acid and the corresponding products were obtained in excellent yields and short reaction times. The catalyst was characterized using Fourier transform infrared and diffuse reflectance UV–visible spectroscopies, scanning electron microscopy and elemental analysis. After each reaction, the catalyst was recovered easily by simple filtration and reused several times without significant loss of its catalytic activity. Copyright © 2015 John Wiley & Sons, Ltd.     

Palladium‐Catalyzed Direct C2‐Arylation of an N‐Heterocyclic Carbene: An Atom‐Economic Route to Mesoionic Carbene Ligands

Blocking the C2 position of an imidazole‐derived classical N‐heterocyclic carbene (NHC) with an aryl group is an essential strategy to establish a route to mesoionic carbenes (MICs), which coordinate to the metal via the C4 (or C5) carbon atom. An efficient catalytic route to MIC precursors by direct arylation of an NHC is reported. Treatment of 1,3‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene (IPr) with an aryl iodide (RC₆H₄I) in the presence of 0.5 mol % of [Pd₂(dba)₃] (dba=dibenzylideneacetone) precatalyst affords the C2‐arylated imidazolium salts {IPr(C₆H₄R)}I (R=H, 4‐Me, 2‐Me, 4‐OMe, 4‐COOMe) in excellent (up to 92 %) yields. Treatment of {IPr(C₆H₅)}I with CuI and KN(SiMe₃)₂ exclusively affords the MIC–copper complex [(IPrPh)CuI].