Copper and nickel immobilized on cytosine@MCM-41: as highly efficient,reusable and organic–inorganic hybrid nanocatalysts for the homoselective synthesis of tetrazoles and pyranopyrazoles

In this work, a green approach is reported for efficient synthesis of biologically active tetrazole and pyranopyrazole derivatives in the presence of Cu-Cytosine@MCM-41 and Ni-Cytosine@MCM-41 (copper (II) and nickel (II) catalyst on the modified MCM-41 using cytosine). The synthesis of tetrazoles and pyranopyrazoles in the presence of these catalysts was performed in green solvents such as water or poly (ethylene glycol) (PEG). All products were obtained in high TOF (turnover frequency) numbers in the presence of these catalysts, which indicate the high efficiency of these catalysts in the synthesis of tetrazole and pyranopyrazole derivatives. The prepared catalysts were characterized by various techniques such as BET, TGA, XRD, FT-IR, SEM, EDS, WDX, TEM, and AAS. Mesoporous structure of these catalysts was confirmed by nitrogen adsorption–desorption isotherms. These catalysts can be recovered and reused for several runs without significant change in their catalytic activity or metal capacity. The recovered catalysts have been characterized by XRD, SEM, EDS, WDX, FT-IR and AAS techniques, by which their heterogeneous nature has been confirmed.     

2-Aminoethanesulfonic acid: An efficient organocatalyst for green synthesis of spirooxindole dihydroquinazolinones and novel 1,2-(dihydroquinazolin-3(4H)isonicotinamides in water

Abstract

A facile and efficient one-pot procedure for the preparation of spirooxindole dihydroquinazolinone derivatives and new N-(4-oxo-2-phenyl-1,2-dihydroquinazolin-3(4H)-yl)isonicotinamides from reaction between isatoic anhydride, isoniazid and substituted aldehydes catalyzed by 2-aminoethanesulfonic acid (taurine) is describe. This new protocol has the advantages of environmental friendliness, good yields, and convenient operation. The reaction proceeds efficiently using water as green solvent and nontoxic catalysts that could be efficiently reused. Together with this simple workup procedure, use of the organocatalyst, and water as solvent without the need of column chromatographic purification, are the notable features of this methodology, which make this protocol a very efficient and green alternative to the traditional methods.     

Bis(imino)pyridine palladium(II) complexes: Synthesis, structure and catalytic activity

Bis(imino)pyridine palladium(II) complexes 3-6 were synthesized by two different methods. The structure of complexes 3 and 4 has been confirmed by X-ray structure analysis. The catalytic studies show that bis(imino)pyridine palladium(II) complexes are highly efficient catalysts in the Suzuki-Miyaura reaction and the complex 4 was used to catalyze the synthesis of fluorinated liquid crystalline compounds via Suzuki coupling reaction.     

Hydrocyanation of Unsaturated Imines Using Potassium Hexacyanoferrate(II) as a Cyanide Source

An efficient method for the hydrocyanation of unsaturated imines to synthesize β,γ‐unsaturated α‐aminonitriles by a one‐pot two‐step procedure using potassium hexacyanoferrate(II) as a cyanide source and benzoyl chloride as a promoter under catalyst‐free condition is described. The advantages of this protocol are the use of a nontoxic, nonvolatile and inexpensive cyanating agent, no use of transition metal catalysts, high yield and simple work‐up procedure.     

Synthesis of Some Novel Class of Bis(isoxazoline) and Bis(aziridine) Derivatives

Synthesis of some new bis(isoxazoline) derivatives has been described from terepthaldehyde derived bis(nitrones) using microwave irradiation via 1,3‐dipolar cycloaddition reaction. Bis(isoxazoline) derivatives in turn successfully converted into new bis(aziridine) derivatives via Baldwin rearrangement. Simple reaction methodology, non involvement of catalysts, and good to excellent yields are the important features noticed in this synthesis.     

磷含量对NiMo/γ-Al2O3催化剂活性相结构的影响

采用程序升温还原（TPR）、高分辨透射电镜（HRTEM）和X射线光电子能谱（XPS）表征手段对共浸渍法制备的不同磷含量NiMo/γ-Al₂O₃催化剂进行了表征,研究了磷含量对NiMo/γ-Al₂O₃催化剂活性相结构的影响。TPR研究表明,磷能够减少四面体配位Mo物种的数量,增加八面体配位Mo物种的数量,促进高活性Ⅱ型"Ni-Mo-S"活性相的形成。HRTEM研究表明,随磷含量的增加,MoS₂颗粒堆积层数增加,催化剂的加氢选择性提高;适量磷能够增加边角位有效Mo原子的分散度(fMo),增加催化剂表面加氢脱硫（HDS）和加氢脱氮（HDN）活性位的数量。上述结论得到了XPS表征的证实：适量磷增加了催化剂表面Mo原子浓度、提高有效助剂比率（PR）和提升比率（Ni/Mo）,相应催化剂表现出最高的HDS和HDN活性;但过高磷含量能够引起MoS₂颗粒过度堆积,片层长度过长,导致活性位数量减少,催化活性降低。     

Dynamic behaviour of chlorofluoroethanes at fluorinated chromia aerogels and fluorinated zinc(II) or magnesium(II) doped chromia aerogels

The preparation and characterisation of two series of fluorinated chromia aerogel materials, lightly doped with zinc(II) or magnesium(II), are described. They behave as heterogeneous catalysts for transformations of 1,1,2-trichlorotrifluoroethane under HF-free conditions and at moderate temperatures. Product distributions depend critically on the contact time. When the latter is very long (static conditions) the surface becomes chlorinated, notwithstanding its fluorinated nature. Rather surprisingly, in view of previous work, the catalytic behaviour of the materials is almost identical to that of the undoped fluorinated chromia aerogel. The nature of reactions occurring under HF-free conditions and low levels of doping achievable are discussed as possible factors in determining catalytic behaviour.     

Metal complexes with polymeric ligands: Chelation and metalloinitiation approaches to metal tris(bipyridine)‐containing materials

Synthetic approaches to metal complexes with polymeric ligands are described. The development of efficient methods for preparing simple bipyridine (bpy) derivatives and their corresponding metal complexes has facilitated their use as initiators and coupling agents in polymer syntheses. Ligand reagents were utilized as initiators in controlled polymerization reactions to form poly(2‐R‐2‐oxazolines) (R = methyl, ethyl, phenyl, undecyl), polystyrenes, poly(methyl methacrylates) (PMMA)s, poly(ϵ‐caprolactone)s, and poly(lactic acid)s with bipyridine chelates at the end or centers of the chains. Poly(ethylene glycol) macroligands were formed by a chain‐coupling method. Detailed studies of reaction kinetics were performed to determine the scope and limitations of each reaction type with different catalysts and reaction conditions. These results are illustrated for bpyPMMA_n (n = 1 or 2), which was prepared by atom transfer radical polymerization with a CuBr/1,4,4,7,7,10‐hexamethyltriethylenetetraamine catalyst system. Results of the kinetics investigations performed with other ligands and metalloinitiators are summarized. Macroligands thus prepared were coordinated to a labile metal ion, Fe(II), with standard protocols. Ultraviolet–visible spectral data for selected Fe‐centered polymers are provided that confirm the production of the targeted polymeric iron complex products. An inert metal, Ru(II), was used as a template for generating architectural diversity; polymeric complexes with one to six chains emanating from the central core, as well as different heteroarm star products, were prepared. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4704–4716, 2000     

Indium (III) mediated Markovnikov addition of malonates and β-ketoesters to terminal alkynes and the formation of Knoevenagel condensation products

The indium(III) triflate mediated addition of active methylene compounds to terminal alkynes has been expanded to use malonates and low boiling terminal alkynes to form the Markovnikov addition products. Indium(III) chloride and indium(III) bromide were also found to be efficient catalysts. Knoevenagel condensation products were isolated when reactions involved a simple malonate or β-ketoester.     

Immobilization of organorhenium(VII) oxides

In the last decade considerable progress has been made in research on organorhenium(VII) oxide catalysts, particularly with respect to methyltrioxorhenium(VII) (MTO). Heterogeneous systems have been developed with particular emphasis on the supporting systems including inorganic and organic carrier materials. As a result efficient and reasonably selective catalysts are now available for a variety of catalytic reactions like olefin epoxidation in particular and other oxidation reactions, metathesis, etc. Besides the MTO/UHP system, polymer supports for the organometallic catalysts are now also successfully applicable. The systems exhibit in several cases the required properties of stability, selectivity, activity and recyclability.     

Oxidative Coupling of Thiols to Disulfides with Ti(IV) in the Presence of NaI under Air Atmosphere

Ti(IV) as TiCl₃(O₃SCF₃) and TiO(O₂CCF₃)₂ are used as efficient catalysts for oxidative coupling of aliphatic, aromatic and heteroaromatic thiols to their disulfides in the presence of NaI under air atmosphere.     

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.     

Chemistry of silver(III) and some of its compounds: A review

Chemistry of Ag(III), as of other transition elements with higher oxidation state(s), is important as its compounds are effectively used as oxidants, catalysts, fluorinating agents, etc. Some basic chemical properties of Ag(III) and up to date report of several Ag(III) compounds are discussed in this present review.     

Ultrasound-assisted synthesis of diversely functionalized tetrahydro-1H-Indole-4(5H)-one using Brønsted base silica sodium carbonate (SSC) as a catalyst under solvent-free conditions

An ultrasound-promoted, environmentally benign, efficient procedure has been developed for the synthesis of biologically active tetrahydro-1H-indol-4(5H)-one using heterogeneous Brønsted base silica sodium carbonate (SSC) as a catalyst under solvent-free conditions. In comparison to the conventional methods, this efficient green protocol provides remarkable advantages such as good to excellent yields, shorter reaction time, low cost, and easy workup procedure and bypasses the use of hazardous transition-metal catalysts and organic solvents.     

Asymmetric Cyclopropanation Catalyzed by Four Stereoisomers of a Copper-(Schiff-base) Complex with Double Chiral Centers

Catalytic asymmetric cyclopropanation of diazoacetates with olefins has attracted much attention. Those catalysts containing various metals and optically active ligands have been employed for this reaction1,2. The first catalytic asymmetric cyclopropanation reaction was reported in 1966 by Nozaki et al.3. The author used the copper(II) complex 1 bearing a salicyladimine ligand as catalyst though with a low e.e. value of 6%. Aratani and his coworkers designed the copper-(Schiff-base) comp…     

Synthesis of poly(urethane‐imide) using aromatic secondary amine‐blocked polyurethane prepolymer

A set of poly(urethane‐imide)s were prepared using blocked Polyurethane (PU) prepolymer and pyromellitic dianhydride (PMDA). The PU prepolymer was prepared by the reaction of polyether glycol and 2,4‐tolylene diisocyanate, and end capped with N‐methyl aniline. The PU prepolymer was reacted with PMDA until the evolution of carbon dioxide ceased. The effect of tertiary amine catalysts, organo tin catalysts, solvents, and reaction temperature were studied and compared with the poly(urethane‐imide) prepared using phenol‐blocked PU prepolymer. N‐methyl aniline blocked PU prepolymer gave a higher molecular weight poly(urethane‐imide) at a lower reaction temperature in a shorter time. Amine catalysts were found to be more efficient than organo tin catalysts. The reaction was favorable in particular with N‐ethylmorpholine and diazabicyclo(2.2.2)octane (DABCO) as catalysts, and dimethylpropylene urea as a reaction medium. The poly(urethane‐imide)s were characterized by FTIR, GPC, TGA, and DSC analyses. The molecular weight decreased with an increase in reaction temperature. The thermal stability of the PU was found to increase by the introduction of imide component. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4032–4037, 2000     

Effects of metal centers of complexes supported by S,S′-bis(2-pyridylmethyl)-1,2-thioethane on catalytic activities for electrochemical- and photochemical-driven hydrogen production

S,S′-bis(2-pyridylmethyl)-1,2-thioethane (bpte) reacts with MCl₂ (M = Co, Ni, and Fe) to give three complexes, namely, [Co^II(bpte)Cl₂] ( 1 ), [Ni^II(bpte)Cl₂] ( 2 ), and [Fe^II(bpte)Cl₂] ( 3 ), respectively. They all act as catalysts for proton or water reduction to dihydrogen via electrolysis or photolysis. Under an overpotential of 837.6 mV, the electrolysis of a neutral buffer with complex 1 , 2 , or 3 can provide 418 (±3), 555 (±3), and 243 (±3) moles of hydrogen per mole of catalyst per hour (mol H₂/mol catalyst/h), respectively. Under blue light, together with a photosensitizer and ascorbic acid (H₂A) as a sacrificial electron donor, the photolysis of an aqueous solution (pH 4.5) containing complex 1 , 2 , or 3 can afford 9060 (±5), 24,900 (±5), and 10,630 (±5) moles H₂ per mole of catalyst (mol of H₂ [mol of cat]⁻¹) during 83-h irradiation with an average apparent quantum yield of 7.1%, 24%, and 10%, respectively. The results show that the nickel complex [Ni^II(bpte)Cl₂] exhibits a more efficient activity for hydrogen generation than the iron or cobalt species. These findings may offer a new chemical paradigm for the design of efficient catalysts.     

Recent advances of layered double hydroxides–based bifunctional electrocatalysts for ORR and OER

The oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) have attracted increasing attention for the sake of clean, renewable, and efficient energy technologies in recent years. The design of ORR/OER bifunctional electrocatalysts is a challenging task in the promotion of highly efficient rechargeable metal-air batteries as well as regenerative fuel cells. Owing to the wide adaptability of different types and ratios of metals in the interlayer space as well as the adjustable interlayer distance, composite materials with layered double hydroxides (LDHs) and their derivatives have recently been registered as electrode materials and catalysts supports for various electrochemical reactions. This study examines the recent development of bifunctional electrocatalysts based on LDHs for ORR/OER to expand the application of LDHs in the field of energy storage and conversion. Various bifunctional electrocatalysts associated with LDHs are discussed in detail to improve their performance. Finally, existing problems and future prospects for improving the performance of LDHs bifunctional electrocatalysts are proposed.     

商用SCR脱硝催化剂K2O中毒后再生:(NH4)2SO4溶液

利用(NH₄)₂SO₄溶液对K₂O中毒后烟气SCR (selective catalytic reduction)脱硝商用催化剂活性进行再生。采用湿法浸渍法使催化剂表面负载不同质量K₂O,前驱体为KNO₃溶液。经过再生工艺处理后,在不同模拟烟气空速及氧浓度条件下均具有良好的活性。进一步利用离子色谱(IC)、N₂吸附脱附分析(BET)、扫描电镜及其元素能谱分析(SEM-Maps, EDX)、红外光谱分析(FT-IR)等技术对再生前后催化剂进行表征。结果表明,再生工艺对K₂O去除效果明显,有效地恢复了催化剂表面活性位V=O。此外,再生过程没有导致催化剂表面物质的流失及机械强度的降低。     

Spectrophotometric study of coproporphyrin-I complexes of copper(II) and cobalt(II)

The reagent 3,8,13,18-tetramethyl-21H,23H-porphine-2,7,12,17-tetrapropionic acid or coproporphyrin-I (CPI) was used for the spectrophotometric determination of copper(II) and cobalt(II) in the presence of pyridine and imidazole catalysts. Optimum conditions were investigated and the methods were applied to the determination of parts per billion levels of copper(II) and cobalt(II). The Sandell sensitivities of the recommended procedures were 0.568 μm cm⁻² and 0.464 μg cm⁻² (for A = 0.001) for copper and cobalt, respectively. The relative standard deviations were 2.0% for copper and 1.0% for cobalt. The kinetics of the reaction of CPI with copper(II) and cobalt(II) in the presence of the catalysts and the influence of the temperature were studied, and their kinetic constants determined.The influence of light on the photodecomposition of CPI was also studied.