Intramolecular O‐arylation using nano‐magnetite supported N‐heterocyclic carbene‐copper complex with wingtip ferrocene

Nano‐magnetite supported N‐heterocyclic carbene‐copper complex with wingtip ferrocene has been prepared via multi‐step procedure. The complex has been characterized by various analytical techniques such as fourier transform infrared (FT‐IR), fourier transform Raman (FT‐Raman), X‐ray photoelectron spectroscopy (XPS), X‐ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM) analysis. The catalytic activity of the complex has been exploited in intramolecular O‐arylation of o‐iodoanilides under heterogeneous conditions. The complex could be successfully recycled up to twelve consecutive cycles.     

Synthesis,characterization and application of 3‐methyl‐1‐sulfonic acid imidazolium tetrachloroferrate as nanostructured catalyst for the tandem reaction of β‐naphthol with aromatic aldehydes and amide derivatives

3‐methyl‐1‐sulfonic acid imidazolium tetrachloroferrate {[Msim]FeCl₄} was prepared and fully characterized by fourier transform infrared spectroscopy (FT‐IR), X‐ray diffraction (XRD), thermal gravimetric analysis (TGA), differential thermal gravimetric (DTG), field emission scanning electron microscopy (FESEM), energy dispersive X‐ray analysis (EDX) and vibrating sample magnetometer (VSM) and used, as an efficient catalyst, for the tandem reaction of β‐naphthol with aromatic aldehydes and benzamide at 110 °C under solvent‐free conditions to give 1‐amidoalkyl‐2‐naphthols in high yields and very short reaction times.     

Kryptofix 5 as an inexpensive and efficient ligand for the palladium‐catalyzed Mizoroki‐Heck reaction

A novel complex of PdCl₂ with a multidentate cryptand ligand, Kryptofix 5, has been prepared and characterized by various techniques including ¹H‐ and ¹³C NMR spectroscopy, Fourier transform infrared (FT‐IR), Raman, ultraviolet and visible (UV‐VIS) spectroscopy, inductively coupled plasma (ICP), CHN elemental and energy dispersive X‐ray analysis (EDX). This heat‐ and air‐stable complex was utilized as a highly active catalyst for the Mizoroki‐Heck reaction of aryl halides with various olefins. Interestingly, it was found that aryl bromides as well as aryl iodides were efficiently cross‐coupled with terminal alkenes at 130 °C in 10 min. Furthermore, the least reactive aryl chlorides reacted with styrene to obtain the desired products in acceptable yields.     

Dendrimer‐encapsulated Cu(Π) nanoparticles immobilized on superparamagnetic Fe3O4@SiO2 nanoparticles as a novel recyclable catalyst for N‐arylation of nitrogen heterocycles and green synthesis of 5‐substituted 1H‐tetrazoles

In this study, dendrimer‐encapsulated Cu(Π) nanoparticles immobilized on superparamagnetic Fe₃O₄@SiO₂ nanoparticles were prepared via a multistep‐synthesis. Then, the synthesized composite was fully characterized by various techniques such as fourier transform infrared (FT‐IR) spectroscopy, X‐ray diffraction (XRD), dynamic light scattering (DLS), UV‐vis spectroscopy, energy dispersive X‐ray analysis (EDX), thermogravimetric analysis (TGA) and vibration sample magnetometer (VSM). From the information gained by FE‐SEM and TEM studies it can be inferred that the particles are mostly spherical in shape and have an average size of 50 nm. Also, the amount of Cu is determined to be 0.51 mmol/g in the catalyst by inductively coupled plasma (ICP) analyzer. This magnetic nano‐compound has been successfully applied as a highly efficient, magnetically recoverable and stable catalyst for N‐arylation of nitrogen heterocycles with aryl halides (I, Br) and arylboronic acids without using external ligands or additives. The catalyst was also employed in a one‐pot, three‐component reaction for the efficient and green synthesis of 5‐substituted 1H‐tetrazoles using various aldehydes, hydroxylamine hydrochloride and sodium azide in water. The magnetic catalyst can be easily separated by an external magnet bar and is recycled seven times without significant loss of its activity.     

Synthesis and characterization of a novel organic–inorganic hybrid salt and its application as a highly effectual Brønsted–Lewis acidic catalyst for the production of N,N′‐alkylidene bisamides

In this research, a novel organic–inorganic hybrid salt, namely, N¹,N¹,N²,N²‐tetramethyl‐N¹,N²‐bis(sulfo)ethane‐1,2‐diaminium tetrachloroferrate ([TMBSED][FeCl₄]₂) was prepared and characterized by Fourier‐transform infrared spectroscopy (FT‐IR), energy‐dispersive X‐ray spectroscopy (EDX), elemental mapping, field emission scanning electron microscopy (FE‐SEM), X‐ray diffraction (XRD), thermal gravimetric (TG), differential thermal gravimetric (DTG), and vibrating‐sample magnetometry (VSM) analyses. Catalytic activity of the hybrid salt was tested for the synthesis of N,N′‐alkylidene bisamides through the reaction of benzamide (2 eq.) and aromatic aldehydes (1 eq.) under solvent‐free conditions in which the products were obtained in high yields and short reaction times. The catalyst was superior to many of the reported catalysts in terms of two or more of these factors: the reaction medium and temperature, yield, time, and turnover frequency (TOF). [TMBSED][FeCl₄]₂ is a Brønsted–Lewis acidic catalyst; there are two SO₃H groups (as Brønsted acidic sites) and two tetrachloroferrate anions (as Lewis acidic sites) in its structure. Highly effectiveness of the catalyst for the synthesis of N,N′‐alkylidene bisamides can be attributed to synergy of the Brønsted and Lewis acids and also possessing two sites of each acid.     

Zn3(BTC)2 as a Highly Efficient Reusable Catalyst for the Synthesis of 2‐Aryl‐1H‐Benzimidazole

Zn₃(BTC)₂ metal‐organic frameworks as recyclable and heterogeneous catalysts were effectively used to catalyze the synthesis of benzimidazole derivatives from o‐phenylendiamine and aldehydes in ethanol. This method provides 2‐aryl‐1H‐benzimidazoles in good to excellent yields with little catalyst loading. The catalyst was characterized using different techniques such as X‐ray diffraction (XRD), energy dispersive X‐ray (EDX) analysis, scanning electron microscopy (SEM), and Fourier transform infrared (FT‐IR) spectroscopy.     

Preparation and characterization of Cu (II) supported on poly(8‐hydroxyquinoline‐p‐styrene sulphonate) and its application as catalyst for the synthesis of hexahydroquinolines

Cu ( II ) supported on poly(8‐hydroxyquinoline‐p‐styrenesulfonate) (Cu ( II )@PHQSS) was prepared and fully characterized by the different techniques including fourier transform infrared spectroscopy (FT‐IR), ¹H NMR, ¹³C NMR, thermal gravimetric analysis (TGA), differential thermal gravimetric (DTG), differential thermal analysis (DTA), scanning electron microscope (SEM) and energy dispersive X‐ray analysis (EDS). Afterward, the Cu ( II )@PHQSS as nanostructured catalyst was used as catalyst for the synthesis of hexahydroquinolines.     

Diethyldisulfoammonium chlorometallates as heterogeneous Brønsted–Lewis acidic catalysts for one‐pot synthesis of 14‐aryl‐7‐(N‐phenyl)‐14H‐dibenzo[a,j]acridines

A new series of Brønsted–Lewis acidic diethyldisulfoammonium chlorometallates, [DEDSA][FeCl₄] and [DEDSA]₂[Zn₂Cl₆], were synthesized as solid materials from the reaction of [(Et)₂N(SO₃H)₂][Cl] ionic liquid with transition metal chlorides (FeCl₃ and ZnCl₂) at 80 °C in neat condition for 2 h. The chlorometallates were fully characterized using various spectroscopic and analytical techniques such as Fourier transform infrared, UV–visible and Raman spectroscopies, powder X‐ray diffraction, scanning electron microscopy, energy‐dispersive X‐ray and thermogravimetric analyses, Hammett acidity and elemental analyses. Their catalytic activity was studied as reusable heterogeneous catalysts for the three‐component synthesis of novel 14‐aryl‐7‐(N‐phenyl)‐14H‐dibenzo[a,j]acridines under solvent‐free conditions at 100 °C.     

Introduction of organic/inorganic Fe3O4@MCM‐41@Zr‐piperazine magnetite nanocatalyst for the promotion of the synthesis of tetrahydro‐4H‐chromene and pyrano[2,3‐d]pyrimidinone derivatives

Fe₃O₄@MCM‐41@Zr‐MNPs modified with piperazine is easily prepared and characterized using Fourier transform infrared spectroscopy (FT‐IR), X‐ray powder diffraction (XRD), N₂ adsorption–desorption, Transmission electron microscopy (TEM), Energy‐dispersive X‐ray (EDX), Vibrating sample magnetometry (VSM) and Thermogravimetric analysis (TGA) techniques. The characterization results showed that Zr highly dispersed in the tetrahedral environment of silica framework and piperazine is successfully attached to the surface of the nanocatalyst in connection with zirconium. The prepared nanosized reagent (10–30 nm), shows excellent catalytic activity in the synthesis of tetrahydro‐4H‐chromene and pyrano[2,3‐d]pyrimidinone derivatives. All reactions are performed under mild and completely heterogeneous reactions conditions in high yields during short reaction times. On the other hand and due to its superparamagnetic nature the catalyst can be easily separated by the application of an external magnetic field and reused for several times.     

In situ green synthesis of Cu‐Ni bimetallic nanoparticles supported on reduced graphene oxide as an effective and recyclable catalyst for the synthesis of N‐benzyl‐N‐aryl‐5‐amino‐1H‐tetrazoles

In the present work, for the first time we have designed a novel approach for the synthesis of N‐benzyl‐N‐aryl‐5‐amino‐1H‐tetrazoles using reduced graphene oxide (rGO) decorated with Cu‐Ni bimetallic nanoparticles (NPs). In situ synthesis of Cu/Ni/rGO nanocomposite was performed by a cost efficient, surfactant‐free and environmentally benign method using Crataegus azarolus var. aronia L. leaf extract as a stabilizing and reducing agent. Phytochemicals present in the extract can be used to reduce Cu²⁺ and Ni²⁺ ions and GO to Cu NPs, Ni NPs and rGO, respectively. Analyses by means of FT‐IR, UV–Vis, EDS, TEM, FESEM, XRD and elemental mapping confirmed the Cu/Ni/rGO formation and also FT‐IR, NMR, and mass spectroscopy as well as elemental analysis were used to characterize the tetrazoles. The Cu/Ni/rGO nanocomposite showed the superior catalytic activity for the synthesis of N‐benzyl‐N‐aryl‐5‐amino‐1H‐tetrazoles within a short reaction time and high yields. Furthermore, this protocol eliminates the need to handle HN₃.     

Synthesis,crystal structures,spectral FT‐IR,NMR and UV–Vis investigations and Hirshfeld surface analysis of two new 2‐hydroxyethyl‐substituted N‐heterocyclic carbene precursors

This study discusses the synthesis of two new 2‐hydroxyethyl substituted N‐heterocyclic carbene (NHC) precursors. The NHC precursors were prepared from 1‐(alkyl/aryl)benzimidazole and alkyl halides. They were characterized using ¹H NMR, ¹³C NMR, FT‐IR, UV–Vis spectroscopy, and elemental analysis techniques. Molecular and crystal structures of 1 and 2 were determined using the single‐crystal X‐ray diffraction method. Crystal structure of the compounds features NHC precursors and chloride anions. Additionally in 2 , the asymmetric unit has a water molecule, which forms a tetrameric chloride‐hydrate assembly with the chloride anion. The chloride anions play an important role in the stabilization of crystal structures to form a two‐dimensional supramolecular architecture. The 3D Hirshfeld surface and the associated 2D fingerprint plots were also drawn to gain insights into the behavior of the interactions in the compounds.     

Chloromethylated polystyrene supported copper (II) bis–thiazole complex: Preparation,characterization and its application as a heterogeneous catalyst for chemoselective and homoselective synthesis of aryl azides

This work deals the synthesis of aryl azides catalyzed by heterogeneous copper (II) complex of 3,5–bis (2–benzothiazolyl) pyridine, [Cu (II)(BTP)(OTf)₂], immobilized on chloromethylated polystyrene, [Cu (II)(BTP)(OTf)₂]@CMP. The prepared catalyst was characterized by different analytical techniques such as X‐ray diffraction (XRD), thermogravimetric analysis (TGA), field emission scanning electron microscopy (SEM), energy dispersive X–ray spectroscopy (EDX), elemental analysis, and FT‐IR and UV–Vis spectroscopic methods. This catalytic system showed excellent activity in the synthesis of aryl azides by the reaction of aryl halides with sodium azide in the presence of catalytic amounts of [Cu (II)(BTP)(OTf)₂]@CMP. Moreover, this unique catalyst could be recovered easily and reused several times without any considerable loss of its catalytic activity.     

Synthesis,Characterization, and Crystal Structure of Three Coordination Polymers from 5‐(Pyridin‐2‐ylmethyl)aminoisophthalic Acid

Three new complexes: [M(L)(H₂O)] [M = Zn ( 1 ), Co ( 2 ), Ni ( 3 ); H₂L = 5‐(pyridin‐2‐ylmethyl)aminoisophthalic acid] were synthesized under hydrothermal conditions at 180 °C and were characterized by elemental analysis, FT‐IR spectroscopy, single‐crystal X‐ray diffraction, and thermogravimetric analysis (TGA). The results of X‐ray diffraction analysis reveal that complexes 1 – 3 are isostructural and crystallize in the monoclinic system with space group P2₁/c. Each of the complexes displays a (3,3′)‐connected two‐dimensional (2D) wave‐like network with (4,8²) topology, within which five‐membered uncoplanar N,N‐chelated metallacycles are shaped. Delicate N–H ··· O and O–H ··· O hydrogen bonding interactions exist in complexes 1 – 3 . Adjacent 2D layers are linked by intermolecular interactions, resulting in the construction of extended metal‐organic frameworks (MOFs) in complexes 1 and 2 .     

Engineering a Cu‐MOF Nano‐Catalyst by using Post‐Synthetic Modification for the Preparation of 5‐Substituted 1H‐Tetrazoles

A new nano scale Cu‐MOF has been obtained via post‐synthetic metalation by immersing a Zn‐MOF as a template in DMF solutions of copper(II) salts. The Cu‐MOF serves as recyclable nano‐catalyst for the preparation of 5‐substituted 1H‐tetrazoles via [3 + 2] cycloaddition reaction of various nitriles and sodium azide in a green medium (PEG). The post‐synthetic metalated MOF were characterized by FT‐IR spectroscopy, powder X‐ray diffraction (PXRD), atomic absorption spectroscopy (AAS), and energy dispersive X‐ray spectroscopy (EDX) techniques. The morphology and size of the nano‐catalyst were determined by field emission scanning electron microscopy (FE‐SEM).     

Mononuclear vs. binuclear carboxylates of copper(II) with 2,2′‐bipyridine: Synthesis,characterization, structural description,and properties

Two new copper(II) carboxylate complexes with 2,2′‐bipyridine and para‐nitrophenyl acetate (complex 1 ) and phenyl acetate (complex 2 ) have been synthesized; isolated in quantitative yield; and characterized using fourier‐transform infrared spectroscopy (FT‐IR), electron paramagnetic resonance, absorption spectroscopy, electrochemistry, and powder and single crystal X‐ray diffraction (XRD) techniques. Being mononuclear, the geometry around copper in complex 1 is a Jahn–Teller distorted octahedral, while complex 2 is binuclear with slightly distorted square pyramidal geometry around both copper ions. Powder XRD indicated several peaks in spectra of both complexes, which coincided with their theoretical spectra. FT‐IR results of the carboxylate stretching frequency were in accordance with the single crystal structure data. Electron paramagnetic resonance spectra of complexes 1 and 2 yielded g_┴ values of 2.06161 and 2.24623 and 1.94959, respectively, indicating a localized electron in b₁ (d _x²_–y²‐orbital). Ultra‐violet (UV)–visible spectroscopy and electrochemistry helped in characterization, as well as in deoxyribonucleic acid (DNA)‐binding ability of the complexes, yielding DNA‐binding constant values = 1.351 × 10⁴ and 1.361 × 10⁴ and 1.820 × 10⁴ and 2.426 × 10⁴ M^?1, respectively, for complexes 1 and 2 . The complexes demonstrate good biological potential.     

Fe3O4‐supported Schiff‐base copper (II) complex: A valuable heterogeneous nanocatalyst for one‐pot synthesis of new pyrano[2,3‐b]pyridine‐3‐carboxamide derivatives

A novel Cu (II) Schiff‐base complex immobilized on core‐shell magnetic Fe₃O₄ nanoparticles (Fe₃O₄@SPNC) was successfully designed and synthesized. The structural features of these nanoparticles were studied and confirmed by using various techniques including FT‐IR spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy‐dispersive X‐ray spectroscopy (EDS), vibrating sample magnetometer (VSM), X‐Ray diffraction (XRD), wavelength dispersive X‐ray spectroscopy (WDX), and inductively coupled plasma (ICP). These newly synthesized nanoparticles have been used as efficient heterogeneous catalytic system for one‐pot multicomponent synthesis of new pyrano[2,3‐b]pyridine‐3‐carboxamide derivatives. Notably, the catalyst could be easily separated from the reaction mixture by using an external magnet and reused for several successive reaction runs with no significant loss of activity or copper leaching. The present protocol benefits from a hitherto unreported MNPs‐immobilized Cu (II) Schiff‐base complex as an efficient nanocatalyst for the synthesis of newly reported derivatives of pyrano[2,3‐b]pyridine‐3‐carboxamide from one‐pot multicomponent reactions.     

A High Sensitive TNT Sensor Based on Electrochemically Reduced Graphene Oxide‐Poly(amidoamine) Modified Electrode

In this paper, the electrochemically reduced graphene oxide‐poly(amidoamine) hybrid (ErGO‐PAMAM) have been used for fabrication of TNT electrochemical sensor. The prepared modified electrode is characterized with X‐ray photoelectron spectroscopy (XPS), fourier transform infrared spectroscopy (FT‐IR), electrochemical impedance spectroscopy (EIS), energy‐dispersive X‐ray (EDX) spectroscopy, scanning electron microscopy (SEM) and atomic force microscope (AFM). Based on obtained results, it is can be seen that the ErGO‐PAMAM/GCE has high response to TNT than the other graphene based modified electrodes. The resulting electrochemical sensor exhibited good response to TNT with linear range from 0.05 to 1.2 ppm with a low detection limit of 0.0015 ppm.     

Solid‐state thermal stability and degradation of a family of poly(N‐isopropylacrylamide‐co‐hydroxymethylacrylamide) copolymers

There is widespread interest in responsive polymers that show cloud point behavior, but little attention is paid to their solid state thermal properties. To manufacture products based on such polymers, it may be necessary to subject them to high temperatures; hence, it is important to investigate their thermal behavior. In this study, we characterized a family of poly(N‐isopropylacrylamide‐co‐hydroxymethylacrylamide) copolymers. Although poly(N‐isopropylacrylamide) shows very high thermal stability (up to 360 °C), introduction of hydroxy side chains leads to a significant reduction in stability and new degradation processes become apparent. Thermogravimetric analysis and fourier transform infrared spectroscopy (FT‐IR) indicate that the first degradation process involves a chemical dehydration step (110–240 °C), supported by the nonreversing heat flow response in modulated temperature differential scanning calorimetry. Water loss scales with the fraction of hydroxy monomer in the copolymer. Glass transition temperatures (T_g) are higher than the temperatures causing dehydration; hence, these values relate to newly‐formed copolymer structures produced by controlled heating under nitrogen. Fourier transform‐Raman (FT‐Raman) spectra suggest that this transition involves imine formation. The T_g increases as the fraction of hydroxy groups in the original copolymer increases. Further heating leads to degradation and mass loss, and more complex changes in the FT‐IR spectra, consistent with formation of unsaturated species. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

H3PW12O40/mpg‐C3N4 as an efficient and reusable catalyst in the alkylation of o‐xylene and styrene

A heterogeneous catalyst (HPW/mpg‐C₃N₄) for the alkylation of o‐xylene and styrene reaction was acquired by the immobilization of phosphotungstic acid (HPW) on mesoporous graphitic carbon nitride (mpg‐C₃N₄) through electrostatic interaction. The results of Fourier transform infrared spectroscopy (FT‐IR), X‐ray powder diffraction (XRD), X‐ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA) proved that HPW was successfully immobilized on the protonated mpg‐C₃N₄ by electrostatic interaction. The textural properties and morphology of HPW/mpg‐C₃N₄ were characterized by N₂ adsorption–desorption, scanning electron microscopy (SEM). Among them, 40% HPW/mpg‐C₃N₄ displays the best catalytic performance in the alkylation reaction with 91.8% yield and 96.5% selectivity to 1, 2‐diphenylethylane. Moreover, protonated mpg‐C₃N₄ not only displays as a support to facilitate great dispersion of HPW but also promotes the alkylation product diffusion effectively. Besides, the HPW/mpg‐C₃N₄ catalyst could be recycled easily without significant loss of catalytic activity, which is demonstrate by the recyclability of HPW/mpg‐C₃N₄ catalyst test.     

Zinc (II), palladium (II) and cadmium (II) complexes containing 4‐methoxy‐N‐(pyridin‐2‐ylmethylene) aniline derivatives: Synthesis,characterization and methyl methacrylate polymerization

A series of Zn (II), Pd (II) and Cd (II) complexes, [(L) _n MX ₂ ] _m (L = L‐a–L‐c; M = Zn, Pd; X = Cl; M = Cd; X = Br; n, m = 1 or 2), containing 4‐methoxy‐N‐(pyridin‐2‐ylmethylene) aniline ( L‐a ), 4‐methoxy‐N‐(pyridin‐2‐ylmethyl) aniline ( L‐b ) and 4‐methoxy‐N‐methyl‐N‐(pyridin‐2‐ylmethyl) aniline ( L‐c ) have been synthesized and characterized. The X‐ray crystal structures of Pd (II) complexes [L ₁ PdCl ₂ ] (L = L‐b and L‐c) revealed distorted square planar geometries obtained via coordinative interaction of the nitrogen atoms of pyridine and amine moieties and two chloro ligands. The geometry around Zn (II) center in [(L‐a)ZnCl ₂ ] and [(L‐c)ZnCl ₂ ] can be best described as distorted tetrahedral, whereas [(L‐b) ₂ ZnCl ₂ ] and [(L‐b) ₂ CdBr ₂ ] achieved 6‐coordinated octahedral geometries around Zn and Cd centers through 2‐equivalent ligands, respectively. In addition, a dimeric [(L‐c)Cd(μ ‐ Br)Br] ₂ complex exhibited typical 5‐coordinated trigonal bipyramidal geometry around Cd center. The polymerization of methyl methacrylate in the presence of modified methylaluminoxane was evaluated by all the synthesized complexes at 60°C. Among these complexes, [(L‐b)PdCl ₂ ] showed the highest catalytic activity [3.80 × 10⁴ g poly (methyl methacrylate) (PMMA)/mol Pd hr^?1], yielding high molecular weight (9.12 × 10⁵ g mol^?1) PMMA. Syndio‐enriched PMMA (characterized using ¹H‐NMR spectroscopy) of about 0.68 was obtained with T_g in the range 120–128°C. Unlike imine and amine moieties, the introduction of N‐methyl moiety has an adverse effect on the catalytic activity, but the syndiotacticity remained unaffected.