Synthesis of one-pot pyrazolo[4′,3′:5,6]pyrano[2,3-c]phenazin-15-yl) methanone derivatives via a multi-component using Fe3O4@TiO2-SO3H as a recoverable magnetic catalyst under microwave irradiation

ABSTRACT

A new one-pot method for the synthesis four-component of pyrazolo[4′,3′:5,6]pyrano[2,3-c]phenazin-15-yl)methanone derivatives has been developed in the presence of nano Fe₃O₄@TiO₂-SO₃H catalysts (heterogeneous acid) under microwave conditions and in a solvent-free environment at 180?W. One of the benefits of using this catalyst was its re-use in subsequent stages of its reaction without much loss in its activity, which was carried out by an external magnet and recovered. The catalyst was synthesized and characterized by XRD, EDX, TEM, FESEM, TGA-DTA, BET, VSM and AFM. The productivity of the products obtained from this protocol (MAOS) is significantly high and the shorter reaction time in the synthesis process over the reflux method. These results showed advantages for synthesis, such as mild reaction conditions, no use of toxic catalysts in the laboratory, solvent-free environment, low energy consumption and Economically Affordable.     

Microwave‐Assisted Aromatization of 1,3,5‐Trisubstituted 2‐Pyrazolines by Bi(NO3)3 · 5H2O,as a Novel and Convenient Oxidizing Agent

Abstract

Bismuth(III) nitrate pentahydrate, Bi(NO₃)₃?·?5H₂O, has been used as a mild, efficient, and inexpensive oxidant for the oxidative aromatization of several 1,3,5‐trisubstituted 2‐pyrazolines to pyrazoles in acetic acid under microwave irradiation with good to excellent yields.     

Simple but efficient synthesis of novel substituted benzimidazoles over ZrO2-Al2O3

Solid-acid catalytic materials such as ZrO₂-Al₂O₃ containing 80?mol% of ZrO₂ were prepared by the solution combustion method (SCM) using different fuels such as urea, hexamethylene tetramine, glycine, and sucrose. All the prepared solid acid catalytic materials were characterized for their physico-chemical properties like crystalinity, acidity, functionality and morphology. These materials were evaluated for their catalytic activity in the synthesis of a series of novel substituted benzimidazoles. The reaction conditions were optimized by varying the solvents, reaction temperature, weight of solid acid catalyst, molar ratio of the reactants, and reaction time. The ZrO₂-Al₂O₃ solid acid catalytic material prepared by urea as a fuel was found to be highly active, recyclable, and reusable in the synthesis of benzimidazoles. A possible reaction mechanism for the synthesis of benzimidazoles is also proposed.     

A fast synthesis for Zintl phase compounds of Na3SbTe3, NaSbTe2 and K3SbTe3 by microwave irradiation

The microwave irradiation technique was used to prepare three Zintl phase compounds Na₃SbTe₃, NaSbTe₂ and K₃SbTe₃. The as-prepared products were analyzed and characterized by XRD, EDX and SEM techniques. Higher microwave oven power and shorter irradiation time are required for the synthesis of Na₃SbTe₃, whereas lower oven power and longer irradiation time are needed for NaSbTe₂. Moderate microwave irradiation conditions facilitate the formation of pure K₃SbTe₃. Pure phase of Na₃SbTe₃ are directly obtained by this technique for the first time. Compared with the traditional high-temperature solid-state synthesis, the microwave reaction required a considerable shortened reaction time for the preparation of the three Zintl compounds. The initial driving force for these reactions originates from the interaction of microwave electric field with alkali metals (Na and K) and Sb powders.     

Silica-supported perchloric acid and potassium bisulfate as reusable green catalysts for nitration of aromatics under solvent-free microwave conditions

Silica-supported perchloric acid and bisulfate (SiO₂/HClO₄ and SiO₂/KHSO₄) have been developed as reusable green catalysts for nitration of aromatic compounds using NaNO₂ in acetonitrile medium under conventional and solvent-free microwave conditions. The reaction times under microwave irradiation are significantly shorter than conventional method even though the yields obtained in microwave-assisted reactions are comparable with those obtained under reflux conditions.     

Solvent-free sonochemical kabachnic-fields reaction to synthesize some new α-aminophosphonates catalyzed by nano-BF3•SiO2

To obtain a rapid, efficient synthesis of some new α-aminophosphonates, ultrasonic irradiation has been applied to the reaction mixtures containing amine, aromatic or heteroaromatic aldehydes and triethyl phosphite. The Kabachnik-Fields reaction was performed by using nano-BF₃?SiO₂ as a recyclable catalyst under solvent free conditions. Key advantages of this procedure consist in the eco-friendly and highly efficient reaction conditions, high yields, an easy work-up procedure, short reaction times and solvent free conditions. All title compounds were characterized by spectral and elemental analysis. They were further screened for their in vitro antioxidant activity by the DPPH, O^2? and NO methods. The majority of the title compounds showed good antioxidant activity when compared with the standard antioxidants.     

Selective oxidation of octadecan-1-ol to octadecanoic acid over Co3O4/SiO2 catalysts

Factors (reaction temperature, reaction time, flow rate of oxygen, amount of catalyst, etc.) influencing the catalytic properties of Co₃O₄/SiO₂catalyst in the oxidation octadecan-1-ol to octadecanoic acid were investigated. The catalysts were characterized by means of XRD, FT-IR and N₂-adsorption. The experimental results indicate that under the optimal condition the selectivity to octadecanoic acid reached 97.5 % over 5 % Co₃O₄/SiO₂ catalyst.This revised version was published online in December 2005 with corrections to the Cover Date.     

Environmentally Friendly Preparation of 3,4-Dihydropyrimidin-2(1H)-thiones Catalyzed by Al(H2PO4)3

An efficient, facile, simple, and green synthetic protocol for the Biginelli reaction has been developed for the preparation of 3,4-dihydropyrimidin-2(1H)-thione derivatives under thermal and microwave irradiation, solvent-free conditions, in the presence of aluminum hydrogen phosphate, Al(H₂PO₄)₃, as an environmentally friendly heterogeneous recyclable catalyst, in high to excellent yields and short reaction time. In addition, the catalyst could be easily recovered from the reaction mixture by simple filtration and reused several times without any loss of activity.     

Nitration of Aromatic Compounds Catalyzed by Divanadium-Substituted Molybdophosphoric Acid,H<Subscript>5</Subscript>[PMo<Subscript>10</Subscript>V<Subscript>2</Subscript>O<Subscript>40</Subscript>]

Summary. The nitration of aromatic compounds was carried out in the presence of divanadium-substituted molybdophosphoric acid, H₅PMo₁₀V₂O₄₀, as catalyst and a mixture of nitric acid and acetic anhydride as nitrating agent. In the presence of this heteropolyacid the ortho- and para-nitro compounds were obtained in good to excellent yields under mild reaction conditions.     

A novel vapor phase process for aromatic ketone synthesis

The vapor phase catalytic reaction between aromatic carboxylic acid and acetic acid was investigated. Many metal oxides catalyzed the reaction between 2methylbenzoic acid (OTA) and acetic acid (AA) to produce 2methylacetophenone (OMA), and weakly acidic oxides such as Th, U, Ce, and La oxide exhibited higher yield of OMA. The OMA yield depended on the catalyst support. SiO₂, Al₂O₃, TiO₂, and ZrO₂ with a surface area of less than 200 m² g^–1 appeared to be suitable as industrial catalyst supports. CeO₂ on Al₂O₃was chosen as an industrial catalyst for the synthesis of OMA because of higher productivity, longer catalyst life, and lifting of legal restrictions on catalyst handling. This catalyst system can also be applied to the syntheses of acetophenone, nitroacetophenone, and chloroacetophenone.     

CeCl3·7H2O Catalyzed,Microwave-Assisted High-Yield Synthesis of α-Aminophosphonates and their Biological Studies

Abstract

A new class of diethyl(3,5-dibromo-4-hydroxyphenylamino) (substituted phenyl/heterocyclic) methylphosphonates 4(a–j) has been synthesized by one-pot three component simultaneous reaction (Kabachnik–Fields) of 4-amino-2,6-dibromophenol 1, substituted heterocyclic/phenyl aldehydes 2(a–j), and diethylphosphite 3 using a Lewis acid catalyst, CeCl₃·7H₂O (5 mol%) under microwave irradiation as well as conventional conditions. It was observed that microwave irradiation method is more facile, efficient, and advantageous with respect to reaction time and yields. The structures of all the synthesized compounds were supported by analyzing IR, ¹H/¹³C/³¹P NMR, and mass spectral data. The synthesized compounds were screened for their in vitro antimicrobial and antioxidant activities.     

Rapid, efficient, room temperature aromatization of Hantzsch-1,4-dihydropyridines with vanadium(V) salts: superiority of classical technique versus microwave promoted reaction

The aromatization of 1,4-dihydropyridines (1,4-DHPs) employing group 4 (Zr and Hf) and 5 (V, Nb, Ta) elements of periodic system has been studied. The reaction with VOCl₃ in dichloromethane at room temperature afforded products, substituted pyridines, in high-to-excellent yield. For the first time, the formation of charge-transfer complexes (CTCs) has been evidenced in preorganization step between 1,4-DHP and oxidant before electron transfer. The CTC has been formed only in neutral solvents such as dichloromethane and is characterized by intensive coloration. The aromatization of 1,4-DHP with V₂O₅ in refluxing acetic acid has found to be superior over microwave promoted reaction in solventless media. The only reasonable explanation was found in polymeric structure of V₂O₅, which slowly transfer energy of microwaves needed for the activation of the reactants. The solvent polarity dependent oxidative dealkylation of 4-n-propyl-1,4-DHP has been discovered. Unexpectedly, the reaction in acetic acid afforded only 33% of dealkylated product compared to 91% obtained in dichloromethane under the same reaction conditions.     

H3PW12O40–[bmim][FeCl4]: A novel and green catalyst-medium system for microwave-promoted selective interconversion of alkoxymethyl ethers into their corresponding nitriles, bromides and iodides

In the present work, the catalytic activity of 12-tungstophosphoric acid immobilized on [bmim][FeCl₄] ionic liquid as a highly efficient and eco-friendly catalytic system for rapid and chemoselective direct conversion of MOM- or EOM-ethers into their corresponding nitriles, bromides and iodides under microwave irradiation is reported. In these reactions, the products are obtained in high yields. The catalyst exhibited remarkable reactivity and was reused several times.     

A simple conversion of azlactones into indenones via H3PW12O40/Al2O3 catalyzed intramolecular Friedel-Crafts reaction

A rapid and simple procedure for the synthesis of the indenone derivatives, N-(1-oxo-1H-inden-2-yl)benzamides, via intramolecular Friedel-Crafts (IFC) reaction of (Z)-4-arylidene-2-phenyl-5(4)-oxazolones (azlactones) catalyzed by H₃PW₁₂O₄₀ supported on neutral alumina under microwave irradiation has been developed. The reaction is straightforward and allows easy isolation of the product. The catalyst could be re-used up to four times after simple filtration.     

γ-MnO2的形貌控制及其甲苯液相氧化性能

通过在回流法制备流程中引入CTAB(十六烷基三甲基溴化铵)、PEG6000(聚乙二醇6000)及P123(聚环氧乙烷-聚环氧丙烷-聚环氧乙烷三嵌段共聚物)等表面活性剂对γ-MnO₂催化剂进行形貌控制, 同时采用X射线衍射(XRD)、扫描电镜(SEM)、N₂吸附(BET)、热重分析(TGA)、O₂程序升温脱附(O₂-TPD)以及H₂程序升温还原(H₂-TPR)等技术对不同形貌γ-MnO₂的结构、氧脱附及还原性能进行表征, 并考察了其在常压和无溶剂条件下甲苯选择性氧化反应体系的催化特性. 同时, 对于陈化时间对形貌的影响作用进行了考察. 结果表明: 不同形貌的γ-MnO₂的氧化还原特征及催化活性存在显著差异, 其中在经PEG6000进行修饰的γ-MnO₂中含有较多的阴离子空位及混合价态, 因此有助于分子氧在表面的活化, 具有较高的表面比活性; 而经P123进行表面修饰的γ-MnO₂成晶结构规整、比表面积大, 对甲苯液相直接氧化反应则表现出最佳的质量比活性, 甲苯转化率达18.1%, 含氧化合物总选择性为87.4%, 其中苯甲酸的选择性达到73.2%.     

CuPy2Cl2: A Novel and Efficient Catalyst for Synthesis of Propargylamines Under the Conventional Method and Microwave Irradiation

CuPy₂Cl₂ is an efficient catalyst for the preparation of propargylamines via three-component coupling reaction of aromatic aldehydes, amines, and aromatic alkynes stirred at 95 °C without using any solvent to afford the corresponding products in good yields. The reaction mixture was irradiated at 450 W in a microwave oven to furnish the expected products in excellent yields.     

Synthesis,characterization of SiO2 supported-industrial phosphoric acid catalyst for hydrolysis of NaBH4 solution

Abstract

Tunisian industrial phosphoric acid H₃PO₄ was supported on silica gel SiO₂ (SIPA) to catalyze the hydrolysis reaction of aqueous alkaline sodium borohydride (NaBH₄). The SiO₂ was produced from purified quartz sand using alkali fusion-acidification chemical process. The BET surface area results indicate that the prepared silica gel could reach a specific surface area up to 585 m²/g. The addition of PO₃H₂ functional groups resulted in an increase of surface acidity of SiO₂ catalyst as shown by FT-IR and DTA-DTG spectra. The total acidity of SIPA catalyst was determined by titration to be 2.8?mmol H⁺/g. SEM/EDS maps reveal the distribution of heavy metals on the silica surface. The effect of supported PO₃H₂ functional groups and heavy metals on the NaBH₄ hydrolysis reaction was studied for different ratios of SIPA catalyst to NaBH₄. The sample 12SIPA/NaBH₄ leads to a very high hydrogen generation rate (up to 90%). The activation energy of hydrogen generation by NaBH₄ hydrolysis was 25.7?kJ mol^?1.     

Bifunctional Catalysts Based on m‐Phenylene‐Bridged Porphyrin Dimer and Trimer Platforms: Synthesis of Cyclic Carbonates from Carbon Dioxide and Epoxides

Highly active bifunctional diporphyrin and triporphyrin catalysts were synthesized through Stille coupling reactions. As compared with a porphyrin monomer, both exhibited improved catalytic activities for the reaction of CO₂ with epoxides to form cyclic carbonates, because of the multiple catalytic sites which cooperatively activate the epoxide. Catalytic activities were carefully investigated by controlling temperature, reaction time, and catalyst loading, and very high turnover number and turnover frequency were obtained: 220 000 and 46 000 h^?1, respectively, for the magnesium catalyst, and 310 000 and 40 000 h^?1, respectively, for the zinc catalyst. Results obtained with a zinc/free‐base hybrid diporphyrin catalyst demonstrated that the Br^? ions on the adjacent porphyrin moiety also function as nucleophiles.     

Ultrasound-assisted one-pot multi-component synthesis of 2-pyrrolidinon-3-olates catalyzed by Co3O4@SiO2 core–shell nanocomposite

2-pyrrolidinon-3-olates were synthesized via one-pot four-component reaction of 2-aminobenzothiazole, aromatic aldehydes, dimethyl acetylenedicarboxylate and morpholine/piperidine in the presence of Co₃O₄@SiO₂ core–shell nanocomposite as catalyst under ultrasound irradiation. The protocol offers several such advantages as high yields, short reaction time and mild reaction conditions with reusability of the catalyst. The core–shell nanocomposite was also prepared using ultrasound irradiation and the structure and magnetic properties were fully characterized by TEM, FE-SEM, XRD, EDX, FT-IR and VSM analysis.     

铁酸钴纳米粒子:室温下点击合成亚芳基巴比妥酸衍生物的高效可磁性分离多相催化剂(英文)

A coprecipitation method was used to synthesize superparamagnetic CoFe2O4 nanoparticles without using any capping agents/surfactants. The prepared nanoparticles were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, a vibrating sample magnetometer (VSM), N2 adsorption and thermogravimetric/differential thermal analysis/differential thermal gravimetry techniques. The synthesized spinel CoFe2O4 nanoparticles had an average size of 2-8 nm with a high surface area (140.9 m2/g). The field-dependent magnetization, demonstrated by VSM and saturation magnetization, was found to be 1.77 emu/g. An efficient method was used for the synthesis of arylidene barbituric acid derivatives using CoFe2O4 magnetic nanoparticles as a magnetically separable and reusable catalyst in aqueous ethanol. The attractive features of this synthetic protocol were very short reaction time, high yields, high turnover frequency, simple work-up procedure, economy, a clean reaction methodology, and chemoselectivity, as well as provision of an ecofriendly and green synthesis.