Ph3BiCO3: a mild reagent for in situ oxidation of urazoles to triazolinediones

A novel method for the selective oxidation of urazoles is reported. The resulting triazolinediones are trapped in situ by cycloaddition with anthracene derivatives. The process described herein involves as mild oxidant, the pentavalent bismuth species Ph₃BiCO₃.     

Silica‐supported perchloric acid as a recyclable catalyst for efficient trimethylsilyl cyanide addition to aldehydes

HClO₄? SiO₂ (0.6 mol%) acts as a highly effective catalyst for cyanation of various aldehydes to the corresponding O‐trimethylsilyl cyanohydrins, in high yields and short reaction times. Copyright © 2007 John Wiley & Sons, Ltd.     

Catalytic oxidation of urazoles and bis-urazoles to their corresponding triazolinediones using aluminium nitrate and a catalytic amount of silica sulfuric acid

Abstract  A simple and efficient catalytic oxidation of urazoles and a bis-urazole to the corresponding triazolinediones by treatment with Al(NO₃)₃.9H₂O in the presence of a catalytic amount of silica sulfuric acid is described. A good range of urazole derivatives was selectively oxidized in CH₂Cl₂ at room temperature in good to excellent yields. Graphical abstract        

Catalytic oxidation of urazoles and bis-urazoles to their corresponding triazolinediones using aluminium nitrate and a catalytic amount of silica sulfuric acid

Abstract  

A simple and efficient catalytic oxidation of urazoles and a bis-urazole to the corresponding triazolinediones by treatment with Al(NO₃)₃.9H₂O in the presence of a catalytic amount of silica sulfuric acid is described. A good range of urazole derivatives was selectively oxidized in CH₂Cl₂ at room temperature in good to excellent yields.     

Tungsten doped mesoporous SBA‐16 as novel heterogeneous catalysts for oxidation of cyclopentene to glutaric acid

Novel heterogeneous tungsten species in mesoporous silica SBA‐16 catalysts based on ship‐in‐a‐bottle methodology are originally reported for oxidizing cyclopentene (CPE) to glutaric acid (GAC) using hydrogen peroxide (H₂O₂). For all W‐SBA‐16 catalysts, isolated tungsten species and octahedrally coordinated tungsten oxide species are observed while WO₃ crystallites are detected for the W‐SBA‐16 catalysts with Si/ W = 5, 10, and 20. The specific surface areas and the corresponding total pore volumes decrease significantly as increasing amounts of tungsten incorporated into the pores of SBA‐16. Using tungsten‐substituted mesoporous SBA‐16 heterogeneous catalysts, high yield of GAC (55%) is achieved with low tungsten loading (for Si/W = 30, ~13 wt%) for oxidation of CPE. The W‐SBA‐16 catalysts with Si/W = 30 can be reused five times without dramatic deactivation. In fact, low catalytic activity provided by bulk WO₃ implies that the highly distributed tungsten species in SBA‐16 and the steric confinement effect of SBA‐16 are key elements for the outstanding catalytic performance.     

Silica‐particle‐supported zwitterionic polymer monolith for microcolumn liquid chromatography

A silica‐particle‐supported zwitterionic polymeric monolithic column, shortened as supported column (S‐column), was prepared by the in situ polymerization of methacrylic acid, ethylene dimethacrylate, and 2‐(dimethylamino)ethyl methacrylate in the presence of a ternary porogenic solvent containing water, methanol, and cyclohexanol in a 250 μm id fused‐silica capillary prepacked with 5 μm bare silica particles. In the S‐column, a thin layer of the polymers was formed around the silica particles in the form of nanoglobules, leaving the interstitial spaces between the particles free for liquid flow. The effects of the preparation conditions on the morphology of the monolith were investigated by scanning electron microscopy and backpressure measurements. The selected volumetric ratio of porogens, monomer concentration, polymerization time, and temperature are 1:1:8 (water/methanol/cyclohexanol), 25% v/v, 5 h, and 60°C, respectively. The S‐column was evaluated by comparison with its conventional organic counterpart in terms of morphology, mechanical stability, permeability, swelling–shrinking behavior, capacity, and efficiency. The results demonstrate that the S‐column is superior to its counterpart in all the terms with the exception of permeability. The above merits and zwitterionic property of the S‐column were further confirmed by separate separations of four inorganic anions and three organic cations.     

石墨相氮化碳负载钒作为多相催化剂用于苯直接氧化制苯酚

苯酚是一种重要的化工原料,目前苯酚的工业生产路线普遍存在工艺流程复杂、苯酚收率低和环境污染严重等问题.为实现苯酚的绿色生产,苯直接氧化制苯酚的合成路线受到各国研究者的广泛关注.在苯直接羟基化反应常用的 N2O, O2和 H2O2三类氧化剂中, N2O由于来源有限,其工业应用受到极大限制;而 O2不易活化,且反应过程中常需还原剂存在,苯酚收率低;相比之下, H2O2作为氧化剂,其唯一副产物是 H2O,而且反应条件温和,因而以 H2O2为氧化剂的苯羟基化反应是最具工业应用前景的苯酚合成路线.然而,由于苯分子中的 C?H键非常稳定,活化能较高,同时产物苯酚的反应活性要高于反应物苯,因此,为实现苯的高效转化,积极探索研究高活性和稳定性的催化剂变得尤为重要.在我们之前的研究中发现,包含大π体系的氧化石墨烯载体有利于具有同样π共轭体系的反应物苯的吸附,进而促进苯的转化,提高反应活性.而石墨相氮化碳(g-C3N4)具有与氧化石墨烯类似的π共轭体系,且表面具有大量的活性位点和缺陷位,对苯环类物质具有较好的活化作用,这使其可能成为更优异的载体材料.基于此,以 g-C3N4为载体,采用浸渍法制备了一系列不同钒含量的催化剂xV/g-C3N4,并通过 XRD, FT-IR, TEM, TG等表征技术对催化剂进行了系统研究,以期揭示催化剂结构与反应活性之间的构效关系. XRD的表征结果表明,xV/g-C3N4仍具有载体 g-C3N4的层状堆积结构,且该结构不受钒负载量变化的影响.同时, xV/g-C3N4中钒物种的分散度较高,未发生团聚晶化.更直观地,通过 TEM观察发现,xV/g-C3N4中的钒物种均匀分散. FT-IR的表征结果说明钒物种与 g-C3N4之间存在较强的相互作用.此外,通过 TG表征发现, g-C3N4高温稳定性较好,即使焙烧温度高达550°C,其结构仍不受影响.综上所述,在xV/g-C3N4催化剂中,载体 g-C3N4的结构非常稳定,经负载钒物种以及焙烧处理后仍能保持不变;而钒物种与 g-C3N4之间存在较强的相互作用,且均匀分散,使催化剂具有较高的稳定性和较好的催化性能.在以 H2O2为氧化剂,80 wt%醋酸溶液为溶剂的苯直接氧化制苯酚反应中,xV/g-C3N4催化剂显示了良好的催化活性,其中反应活性最高的是8V/g-C3N4催化剂,在最佳反应条件下,苯酚的收率和选择性分别达到24.4%和99.2%.同时,通过计算 TOF值发现,8V/g-C3N4的 TOF值高达13.1 h-1,远高于文献中报道的以 C3N4为载体的催化剂的 TOF值(0.52–0.59 h-1),这表明xV/g-C3N4催化剂具有优异的催化活性.此外,以8V/g-C3N4为代表又进一步考察了催化剂的稳定性,在回收重复实验中催化剂的活性保持稳定.     

Tungstate sulfuric acid (TSA)/KMnO4 as a novel heterogeneous system for rapid deoximation

Neat chlorosulfonic acid reacts with anhydrous sodium tungstate to give tungstate sulfuric acid (TSA), a new dibasic inorganic solid acid in which two sulfuric acid molecules connect to a tungstate moiety via a covalent bond. A variety of oximes were oxidized to their parent carbonyl compounds under mild conditions with excellent yields in short times by a heterogeneous wet TSA/KMnO4 in dichloromethane system.     

The first report on the catalytic oxidation of urazoles to their corresponding triazolinediones via in situ catalytic generation of Br using periodic acid or oxone/KBr system

A combination of periodic acid or oxone^® and a catalytic amount of KBr in the presence of few drops of water, were used for the catalytic oxidation of urazoles and bis-urazoles to their corresponding triazolinediones under mild and heterogeneous conditions with moderate to excellent yields.     

Silica‐gel‐supported Phosphorus Pentoxide:a Simple and Efficient Solid‐supported Reagent for Esterification of Long‐ Chain Carboxylic Acids and Their Antimicrobial Screening

A silica-gel-supported heterogeneous phosphorus pentoxide reagent has been developed for the esterification of various long-chain carboxylic acids with aromatic alcohols. The reactions occurred under relatively mild conditions and afforded the desired products in good yields. All the compounds 3a—3x were screened for antibacterial and antifungal activity, which showed good activity against Gram positive and Gram negative bacteria and also good results against almost all fungal strains. The structures of the synthesized compounds were elucidated by IR, ¹H NMR, ¹³C NMR, mass spectroscopic techniques and elemental analysis.     

Silica‐supported Perchloric Acid Catalyzed One‐pot Synthesis of 1,4‐Dihydropyridines

An environmentally friendly and highly efficient procedure for the preparation of 1,4‐dihydropyridines by the reaction between α,β‐unsaturated aldehydes, aromatic amines and β‐keto esters in the presence of silica supported perchloric acid is described.     

Natural hydroxyapatite‐supported MnO2: a green heterogeneous catalyst for selective aerobic oxidation of alkylarenes and alcohols

Natural hydroxyapatite‐supported MnO₂ (MnO₂@NHAp) was easily prepared in situ from reduction of potassium permanganate with natural hydroxyapatite derived from cow bones in water at room temperature, and its structure was characterized using flame atomic absorption spectroscopy, X‐ray diffraction, thermogravimetric analysis, scanning electron microscopy and energy dispersive spectroscopy. The catalytic activity of the synthesized catalyst was investigated for the aerobic oxidation of alkylarenes and alcohols. MnO₂@NHAp shows excellent catalytic performance for the oxidation of alkylarenes and alcohols to their corresponding carbonyl compounds without using any other oxidizing agent. This catalyst can be readily recycled and reused for several runs without any significant loss of efficiency. Copyright © 2016 John Wiley & Sons, Ltd.     

A novel nano‐cotton‐like bismuth oxyfluoride (NC‐BiOF) and a novel nanosheet heterogeneous compound BiOF@ZIF‐8 as catalyst for the selective and green oxidation of benzylic alcohols

We describe here for the first time a new morphology of BiOF nanoparticles with a cotton‐like structure, made using a hydrothermal synthesis method. We also prepared heterogeneous nanosheets of BiOF@ZIF‐8 by a one‐pot synthesis under hydrothermal conditions. We demonstrate that in this method the morphology of BiOF and one‐pot synthesis conditions are the main factors for the preparation of the nanosheet BiOF@ZIF‐8. Fourier transform infrared (FTIR), X‐ray diffraction (XRD), scanning electron microscopy (SEM), energy‐dispersive X‐ray (EDX), thermogravimetry‐differential thermal analysis (TG‐DTA), and BET surface area were used to characterize the samples prepared. XRD, SEM, and adsorption–desorption analysis showed that the structure of ZIF‐8 and BiOF form intact only in one‐pot synthesis of BiOF (with nano‐cotton‐like morphology) with Zn(NO₃)₃, while spectral techniques show the successful encapsulation of the sheet BiOF on ZIF‐8. Nanosheet BiOF@ZIF‐8 was found to be a highly efficient heterogeneous catalyst for the selective oxidation of alcohols. BiOF@ZIF‐8 could be reused several times although it got less active with recycling.     

Silica‐supported terpyridine palladium(II) complex as an efficient and reusable catalyst for Heck and Suzuki cross‐coupling reactions

Silica‐supported terpyridine palladium(II) was prepared and used as an effective and recyclable catalyst in Mizoroki–Heck and Suzuki–Miyaura coupling reactions. The catalyst was very effective for the Mizoroki–Heck reaction of aryl halides with olefins and conversion was in most cases excellent. The catalyst showed good thermal stability (up to 230 °C) and could be recovered and reused for four reaction cycles. The Suzuki coupling of aryl iodides with aryl boronic acids in the presence of the catalyst was also investigated and the reaction proceeded with a short reaction time and excellent conversion. Copyright © 2013 John Wiley & Sons, Ltd.     

Polystyrene‐supported AlCl3 as a highly active and reusable heterogeneous lewis acid catalyst for the one‐pot synthesis of quinoxalines

A new and environmentally benign protocol for the synthesis of quinoxaline derivatives through the condensation reactions of 1,2‐diketones and 1,2‐phenylenediamines using cross‐linked polystyrene‐supported aluminum chloride (PS/AlCl₃) as a highly active and reusable heterogeneous Lewis acid catalyst is described. This polymeric catalyst is stable and can be easily recovered and reused without appreciable change in its efficiency. © 2012 Wiley Periodicals, Inc. Heteroatom Chem 23:472–477, 2012; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.21039     

Silica‐Based Liquid Marbles as Microreactors for the Silver Mirror Reaction

Little attention has been paid to the participation of the shell of silica‐particle‐based liquid marbles and their influence on chemical reactions. The fabrication of liquid marbles with the encapsulating particle shells not only act as protecting layers to provide a confined environment, but also provide the reactive substrate surfaces to regulate the classical silver mirror reaction. Fabrication of silver mirrors with different morphologies was achieved by modifying particle surface properties, which could further lead to Janus liquid marbles. The different evaporation behavior of microreactors was demonstrated. Micrometer‐sized silica particles were used for the preparation of monolayer‐stabilized liquid marbles, which show great potential in fabricating Janus particles from superhydrophobic particles that are not attainable from Pickering emulsions.     

Silica‐supported metallocenes: effect of the preparation procedure on the morphology of polyethylene particles

Polyethylene (PE) particles are produced by a catalyst prepared by contacting a (C₄H₉Cp)₂ZrCl₂/MAO pre‐mixing solution with SiO₂ support. These particles have a large granular size and very few fine particles compared with those derived from a catalyst prepared by adsorption of (C₄H₉Cp)₂ZrCl₂ onto methylaluminoxane modified SiO₂. The amount of Al in the pre‐mixing catalyst has an important effect on its activity and the PE particle size distribution. The optimal concentration is about 30 wt.‐%. The PE particles produced using a pre‐mixing catalyst consist of globules with randomly oriented fiber structure on the surface, whereas those produced using adsorption catalysts have worm‐like fibrils protruding from the PE globule surface.     

Magnetic d‐penicillamine‐functionalized cellulose as a new heterogeneous support for cobalt(II) in green oxidation of ethylbenzene to acetophenone

A new efficient heterogeneous catalyst is introduced for the oxidation of ethylbenzene. The catalyst was obtained in three steps: functionalization of cellulose with d ‐penicillamine, deposition of Fe₃O₄ nanoparticles on cellulose–d ‐penicillamine and then anchoring of Co(II) to the magnetic cellulose–d ‐penicillamine. High yield and excellent selectivity were achieved for the oxidation of ethylbenzene to acetophenone in ethanol under reflux conditions using H₂O₂ as a green oxidant. Also, the recovered catalyst could be applied six times without a decrease in activity.     

Silica‐supported polymeric monolithic column with a mixed mode of hydrophilic and strong cation‐exchange interactions for microcolumn liquid chromatography

A novel sulfonic acid group containing hydrophilic strong cation‐exchange monolith was prepared by in situ coating 5 μm bare silica particles with the copolymers of glycidyl methacrylate and pentaerythritol triacrylate and further sulfonating the prepared polymer matrix with Na₂SO₃ inside a 150 μm id capillary. The preparation conditions were investigated, and the method was described in detail. The prepared column was characterized by comparing with its counterparts reported previously in terms of matrix morphology, preparation reproducibility, permeability, swelling–shrinking behavior, mechanical stability, hydrophilicity, binding capacity, and column efficiency. The swelling–shrinking behavior of the present column in solvents of different polarities was negligible, the hydrophobicity could be suppressed at the acetonitrile concentrations higher than 40% v/v, and the binding capacities were 256 μequiv/mL and 20.1 mg/mL for Cu²⁺ and lysozyme, respectively. The minimum theoretical plate heights were 8, 10, and 13 μm, and the values of the C term in van Deemter equation were 9, 12, and 35 ms for the test analytes of Na⁺, thiourea, and cytidine 5ʹ‐monophosphate, respectively. This column exhibited an excellent performance in the separations of monovalent inorganic cations, uncharged polar, and charged polar compounds.