NH2SO3H–SiO2 as a new water‐compatible,recyclable heterogeneous catalyst for the synthesis of novel (α,β‐unsaturated) β‐amino ketones via aza‐Michael reaction

NH₂SO₃H–SiO₂/water as a novel catalytic system was used for the synthesis of (α,β‐unsaturated) β‐amino ketones via aza‐Michael reaction at reflux conditions. The methodology was of general applicability and the catalyst exhibited activity up to five cycles. The catalyst was characterized for the first time using FT‐IR, X‐ray diffraction and scanning electron microscopic–energy dispersion analytical X‐ray. The stability of the catalyst was evaluated by differential scanning calorimetry and TGA/differential thermal analysis. High efficiency of the catalyst along with its recycling ability and the rather low loading demonstrated in reactions are the merits of the presented protocol. Copyright © 2013 John Wiley & Sons, Ltd.     

Click approach to the three‐component synthesis of novel β‐hydroxy‐1,2,3‐triazoles catalysed by new (Cu/Cu2O) nanostructure as a ligand‐free,green and regioselective nanocatalyst in water

Copper nanostructures were produced as an effective and regioselective catalyst for the synthesis of 1,2,3‐triazoles from a wide range of raw materials, such as sodium azide, epoxides and terminal alkynes, in water via a one‐pot three‐component click reaction. The new heterogeneous catalyst was prepared by a simple ball mill reduction of CuO with NaBH₄ using a ball‐to‐powder weight ratio of 50:1 under air atmosphere at room temperature. The catalyst was fully characterized using scanning electron microscopy, energy‐dispersive X‐ray analysis, Fourier transform infrared spectroscopy and X‐ray diffraction. The copper nanostructures catalysed both ring opening and triazole cyclization steps. Products were obtained in high yields and short reaction times. The reactions were performed at ambient temperature in water as a green solvent. The Cu/Cu₂O nanostructures revealed high reusability and high stability via a simple recycling process.     

A meso–meso β‐β β‐β Triply Linked Subporphyrin Dimer

A meso–meso β‐β β‐β triply linked subporphyrin dimer 6 was synthesized by stepwise reductive elimination of β‐to‐β doubly Pt^II‐bridged subporphyrin dimer 9 . Dimer 6 was characterized by spectroscopic and electrochemical measurements, theoretical calculations, and picosecond time‐resolved transient absorption spectroscopy. X‐ray diffraction analysis reveals that 6 has a bowl‐shaped structure with a positive Gaussian curvature. Despite the curved structure, 6 exhibits a remarkably red‐shifted absorption band at 942 nm and a small electrochemical HOMO–LUMO gap (1.35 eV), indicating an effectively conjugated π‐electronic network.     

Design,synthesis, characterization and catalytic performance of a new cellulose‐based magnetic nanocomposite in the one‐pot three‐component synthesis of α‐aminonitriles

A sulfonated magnetic cellulose‐based nanocomposite was prepared and characterized using scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, X‐ray diffraction and Fourier transform infrared spectroscopy. Then, it was used as a green nanocatalyst for the synthesis of α‐aminonitriles by a one‐pot three‐component condensation reaction of aldehydes or ketones, amines and trimethylsilylcyanide in ethanol at room temperature. The reaction procedure is simple, yields are very high, reaction time is very short and the catalyst can be easily separated from the reaction mixture and reused in subsequent reactions without significant loss of catalytic activity. Copyright © 2016 John Wiley & Sons, Ltd.     

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 cyclohexandiamine/Fe3O4/ZnO core/shell nanomagnetic composite as a novel reusable catalyst and its application for the diastereoselective synthesis of β‐lactams via the asymmetric Kinugasa reaction

A novel magnetic composite catalyst has been prepared by immobilizing a chiral diamine on core/shell Fe₃O₄/ZnO. This new catalyst was characterized using X‐ray diffraction, energy‐dispersive X‐ray analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis and vibrating sample magnetometry. The performance of the catalyst was investigated in the asymmetric Kinugasa reaction and confirmed to be efficient in the synthesis of β‐lactam derivatives under mild conditions.     

Fe3O4@TiO2@O2PO2(CH2)NHSO3H as a novel nanomagnetic catalyst: Application to the preparation of 2‐amino‐4,6‐diphenylnicotinonitriles via anomeric‐based oxidation

A new, green and reusable nanomagnetic heterogeneous catalyst, namely Fe₃O₄@TiO₂@O₂PO₂(CH₂)NHSO₃H, was synthesized and fully characterized using suitable techniques such as infrared spectroscopy, X‐ray diffraction, scanning and transmission electron microscopies, thermogravimetry, vibrating sample magnetometry and energy‐dispersive X‐ray spectroscopy. The applicability of the constructed heterogeneous core–shell catalyst as a promoter was successfully explored for the synthesis of 2‐amino‐4,6‐diphenylnicotinonitrile derivatives upon the reaction of a good range of aromatic aldehydes, acetophenone derivatives, malononitrile and ammonium acetate. The desired products were obtained with good to high yields in short reaction times under solvent‐free conditions. The suggested mechanism offers an anomeric‐based oxidation route to the products in the final step of the synthetic pathway.     

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.     

Terbium–organic framework as heterogeneous Lewis acid catalyst for β‐aminoalcohol synthesis: Efficient,reusable and green catalytic method

A terbium–organic framework (Tb‐MOF) was prepared using a previously reported procedure. Tb‐MOF was characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, powder X‐ray diffraction and surface area analysis. Tb‐MOF was employed as a heterogeneous Lewis acid catalyst for the synthesis of β‐aminoalcohols. Also, the effect of ultrasonic irradiation was examined in the catalytic aminolysis of styrene oxide. The reaction conditions were optimized by variation of reaction time, catalyst concentration and solvent. A variety of β‐aminoalcohols were synthesized and characterized. The Tb‐MOF catalyst showed excellent selectivity and high yield for these transformations.     

Cu(II) immobilized on Fe3O4–diethylenetriamine: A new magnetically recoverable catalyst for the synthesis of 2,3‐dihydroquinazolin‐4(1H)‐ones and oxidative coupling of thiols

Cu(II) immobilized on Fe₃O₄–diethylenetriamine was designed as a new, inexpensive and efficient heterogeneous catalyst for the synthesis of 2,3‐dihydroquinazolin‐4(1H )‐ones and the oxidative coupling of thiols. The structure of the nanomagnetic catalyst was comprehensively characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, vibrating sample magnetometry, thermogravimetric analysis, X‐ray diffraction and atomic absorption spectroscopy. Simple preparation of the catalyst from commercially available materials, high catalytic activity, simple operation, high yields, use of green solvents, easy magnetic separation and reusability of the catalyst with unaltered activity make our protocol a green and feasible synthetic strategy.     

10β‐Acetoxy‐8α,9α‐epoxy‐14β‐hydroxy‐7‐oxodolastane – A New Diterpene Isolated from the Brazilian Brown Macroalga Canistrocarpus cervicornis

Chemical investigation on the nonpolar extract of the Brazilian brown alga Canistrocarpus cervicornis (Dictyotaceae) has led to the isolation of a new diterpene 1 and four known seco‐dolastane diterpenes 2 – 5 . Their chemical structures were elucidated by 1D‐ and 2D‐NMR spectroscopy, and the data was compared with the literature. A full X‐ray diffraction analysis confirmed the absolute configuration of 1 .     

CoFe2O4@SiO2‐CPTES‐Guanidine‐Cu(II): A novel and reusable nanocatalyst for the synthesis of 2,3‐dihydroquinazolin‐4(1H)‐ones and polyhydroquinolines and oxidation of sulfides

CoFe₂O₄@SiO₂‐CPTES‐Guanidine‐Cu(II) magnetic nanoparticles were synthesized and used as a new, inexpensive and efficient heterogeneous catalyst for the synthesis of polyhydroquinolines and 2,3‐dihydroquinazoline‐4(1H)‐ones and for the oxidation of sulfides. The structure of this nanocatalyst was characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, vibrating sample magnetometry, thermogravimetric analysis, X‐ray diffraction and inductively coupled plasma optical emission spectrometry. Simple preparation, high catalytic activity, simple operation, high yields, use of green solvents, easy magnetic separation and reusability of the catalyst are some of the advantages of this protocol.     

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.     

Novel nano molten salt tetra‐2,3‐pyridiniumporphyrazinato‐oxo‐vanadium tricyanomethanide as a vanadium surface‐free phthalocyanine catalyst: Application to Strecker synthesis of α‐aminonitrile derivatives

Efficient and recyclable novel nano tetra‐2,3‐pyridiniumporphyrazinato‐oxo‐vanadium tricyanomethanide, {[VO(TPPA)][C(CN)₃]₄}, as a vanadium surface‐free phthalocyanine‐based molten salt catalyst was successfully designed, produced and used for the Strecker synthesis of α‐aminonitrile derivatives through a one‐pot three‐component reaction between aromatic aldehydes, trimethylsilyl cyanide and aniline derivatives under neat conditions at 50 °C. This catalyst was well characterized using Fourier transform infrared, UV–visible, X‐ray photoelectron and energy‐dispersive X‐ray spectroscopies, X‐ray diffraction, scanning and high‐resolution transmission electron microscopies, inductively coupled plasma mass spectrometry and thermogravimetric analysis. The catalyst can be simply recovered and reused several times without significant loss of catalytic activity.     

Multi‐wall carbon nanotube supported Co (II) Schiff base complex: an efficient and highly reusable catalyst for synthesis of 1‐amidoalkyl‐2‐naphthol and tetrahydrobenzo[b]pyran derivatives

An immobilized Co (II) Schiff base complex supported on multi‐wall carbon nanotubes was synthesized and characterized using Fourier transform infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy , thermogravimetric analysis and inductively coupled plasma mass spectrometry. It was shown that the supported complex is a facile, eco‐friendly, recyclable, reusable and green catalyst for three‐component condensation of 2‐naphthol and acetamide with various aldehydes for the synthesis of 1‐amidoalkyl‐2‐naphthol derivatives under solvent‐free conditions. Also, in a further study, the catalytic application was studied in the synthesis of tetrahydrobenzo[b ]pyran derivatives via the condensation reaction of malononitrile and dimedone with several aromatic aldehydes. The procedures suggested here for the synthesis of 1‐amidoalkyl‐2‐naphthol and tetrahydrobenzo[b ]pyran derivatives offer several advantages, such as stability, recyclability and eco‐friendliness of the catalyst, simple experimental conditions, short reaction times, high to excellent yields and easy work‐up.     

Palladium–S‐propyl‐2‐aminobenzothioate immobilized on Fe3O4 magnetic nanoparticles as catalyst for Suzuki and Heck reactions in water or poly(ethylene glycol)

A moisture‐ and air‐stable heterogenized palladium catalyst was synthesized by coordination of palladium with S‐propyl‐2‐aminothiobenzamide supported on Fe₃O₄ magnetic nanoparticles. The prepared nanocatalyst was characterized using Fourier transform infrared, energy‐dispersive X‐ray and inductively coupled plasma atomic emission spectroscopies, X‐ray diffraction, vibrating sample magnetometry, transmission and scanning electron microscopies, dynamic laser scattering and thermogravimetric analysis. This catalyst could be dispersed homogeneously in water or poly(ethylene glycol) and further applied as an excellent nano‐organometal catalyst for Suzuki and Heck reactions. The catalyst was easily separated with the assistance of an external magnet from the reaction mixture and reused for several consecutive runs without significant loss of its catalytic efficiency or palladium leaching. The leaching of catalyst was examined using hot filtration and inductively coupled plasma atomic emission spectroscopy. Also, the effects of various reaction parameters on the Suzuki and Heck reactions are discussed. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis and reactions of 3‐cyano‐4,6‐dimethyl‐2‐pyridone

Rapid synthesis of 3‐cyano‐4,6‐dimethyl‐2‐pyridone 3 , using piprazine as a catalyst was reported. X‐ray data of the 4,6‐dimethyl‐2‐oxo‐1,2‐dihydropyridine‐3‐carbonitrile exhibited its oxo form. Synthesis of isoquinolinecarbonitrile and pyridylpyridazine using compound 3 was investigated. Reactivity of the synthesized pyridone toward different organic reagents was also studied. J. Heterocyclic Chem., (2011).     

Efficient and Magnetically Recoverable “Click” PEGylated γ‐Fe2O3–Pd Nanoparticle Catalysts for Suzuki–Miyaura,Sonogashira, and Heck Reactions with Positive Dendritic Effects

The engineering of novel catalytic nanomaterials that are highly active for crucial carbon–carbon bond formations, easily recoverable many times, and biocompatible is highly desirable in terms of sustainable and green chemistry. To this end, catalysts comprising dendritic “click” ligands that are immobilized on a magnetic nanoparticle (MNP) core, terminated by triethylene glycol (TEG) groups, and incorporate Pd nanoparticles (PdNPs) have been prepared. These nanomaterials are characterized by transmission electron microscopy (TEM), high‐resolution TEM, inductively coupled plasma analysis, Fourier transform infrared spectroscopy, X‐ray photoelectron spectra and energy‐dispersive X‐ray spectroscopy. They are shown to be highly active, dispersible, and magnetically recoverable many times in Suzuki, Sonogashira, and Heck reactions. In addition, a series of pharmacologically relevant or natural products were successfully synthesized using these magnetic PdNPs as catalyst. For comparison, related PdNP catalysts deposited on MNPs bearing linear “click” PEGylated ligands are also prepared. Strong positive dendritic effects concerning ligand loading, catalyst loading, catalytic activity, and recyclability are observed, that is, the dendritic catalysts are much more efficient than non‐dendritic analogues.     

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.     

A new nano‐Fe3O4‐supported organocatalyst based on 3,4‐dihydroxypyridine: an efficient heterogeneous nanocatalyst for one‐pot synthesis of pyrazolo[3,4‐b]pyridines and pyrano[2,3‐d]pyrimidines

A simple and practical strategy for the synthesis of a novel nano‐Fe₃O₄‐supported organocatalyst system based on 3,4‐dihydroxypyridine (Fe₃O₄/Py) has been developed. The prepared catalyst was characterized using Fourier transform infrared spectroscopy, transmission and scanning electron microscopies, X‐ray diffraction, vibrating sample magnetometry and energy‐dispersive X‐ray analysis. Accordingly, the Fe₃O₄/Py nanoparticles show a superparamagnetic property with a saturation magnetization of 61 emu g^?1, indicating potential application in magnetic separation technology. Our experimental results reveal that the pyridine‐functionalized Fe₃O₄ nanoparticles are an efficient base catalyst for the domino condensation of various aromatic aldehydes, Meldrum's acid and 5‐methylpyrazol‐3‐amine under very mild reaction condition and in the presence of ethanol solvent. Moreover, the synthesized catalyst was used for one‐pot, three‐component condensation of aromatic aldehydes with barbituric acid and malononitrile to produce 7‐amino‐2,4‐dioxo‐5‐phenyl‐2,3,4,5‐tetrahydro‐1H‐pyrano[2,3‐d]pyrimidine‐6‐carbonitriles. All reactions are completed in short times and all products are obtained in good to excellent yields. Also, notably, the catalyst was reused five times without significant degradation in catalytic activity and performance. Copyright © 2016 John Wiley & Sons, Ltd.