镍催化芳烃卤化物还原性交叉偶联的反应机理(英文)

利用密度泛函理论(DFT)计算研究了镍催化的溴苯(R1)与对溴苯甲酸甲酯(R2)生成非对称联芳化合物的还原性交叉偶联反应的机理.结果表明,相对于一价镍的催化机理,零价镍作为活性催化剂更有利于反应的进行,零价镍催化剂首先与R1络合或者首先与R2络合的反应机理十分相似,其决速步在气相时的能垒分别是70.50或者49.66 kJ?mol-1.零价镍催化机理包括如下步骤:一次氧化加成;还原;二次氧化加成;还原消除以及催化剂再生.另外,计算结果还表明有机锌试剂在这个反应体系中很难生成.     

Nanostructured Pyrophosphate Na2PdP2O7‐Catalyzed Suzuki‐Miyaura Cross‐Coupling Under Microwave Irradiation

Nanostructured palladium pyrophosphate (Na₂PdP₂O₇) catalyst was synthesized and well characterized by using different techniques (TGA, XRD, SEM, TEM....). This nanocatalyst exhibited excellent catalytic activity in the synthesis of biaryl compounds via Suzuki‐Miyaura cross‐coupling to produce their corresponding products in good to excellent yields under mild conditions. The catalyst is recyclable and was recycled for four runs for the reaction of 4‐bromoacetophenone with phenylboronic acid without appreciable loss of its catalytic activity.     

Study of urease inhibitory activity by medicinal plants extract based on new catalyst for Berthelot reaction and Taguchi experimental design

The Berthelot reaction is a well-established colorimetric method for determination of ammonia. In this work, the effects of different bivalent ions (Ba²⁺, Cd²⁺, Co²⁺, Cu²⁺, Fe²⁺, Hg²⁺, Mg²⁺, Mn²⁺, Ni²⁺, and Pb²⁺) were studied as catalyst on the Berthelot reaction efficiency. CuCl₂ was generally found as the best catalyst that provides a rapid and stable blue indophenol color. The Taguchi experimental design methodology has been applied to find optimum conditions. Four factors including temperature, pH, reaction time, and CuCl₂ concentration at five levels were considered to achieve optimum conditions. Blue indophenol color stability for 40 min, and linearity response up to 20 mM of ammonium sulfate were achieved by further validation experiments. Limit of detection and quantification for this approach was 0.15 and 0.5 mM, respectively. Inhibitory activity of three traditional medicinal plants extract (Citrus aurantifolia, Laurus nobilis, and Zingiber officinale) was evaluated against jack bean urease activity by Berthelot reaction in the presence of CuCl₂ as catalyst, and results were compared with traditional Berthelot reaction.     

Palladium-catalysed symmetrical and unsymmetrical coupling of aryl halides

Pd(OAc)₂ is a convenient catalyst under basic conditions for the synthesis of symmetrical biaryl moieties from aryl halides. This homocoupling of aryl halides is a good catalytic alternative to classical biaryl formations involving stoichiometric amounts of metal. This method is compatible with sensitive functional groups. We also studied the extension of this reaction to unsymmetrical aryl coupling.     

Kinetic study of methoxycarbonylation of 1,6‐hexanediamine with dimethyl carbonate using Mn(OAc)2 catalyst

Clean synthesis of dimethylhexane‐1,6‐dicarbamate (HDC) from methoxycarbonylation of 1,6‐hexanediamine (HDA) with dimethyl carbonate (DMC) was studied. Among several heterogeneous and homogeneous catalysts, Mn(OAc)₂ was screened as the most effective catalyst over which the kinetic balance could be reached within 2–3 h. Then the kinetic model of the methoxycarbonylation of HDA with DMC using Mn(OAc)₂ catalyst, under the real reaction conditions was established. Results indicated that the reaction orders were confirmed to be 4.5 for the first step reaction and 4.3 for the second step reaction by the numerical differential method. In addition, the activation energies for the first and second step reaction were 47.0514 and 60.4504 kJ·mol⁻¹ and the frequency factors were 1.4645 × 10² and 3.6519 × 10⁴ min⁻¹, respectively. Moreover, the kinetic model correlated well with experimental data. This study not only provides a highly efficient catalyst for the methoxycarbonylation of HDA with DMC but also gives the guidance for the design of the reactor by studying its kinetic under real reaction conditions.     

Hierarchical TiO2 microspheres supported ultrasmall palladium Nanocrystals: A highly efficient catalyst for Suzuki reaction

A hierarchical titanium dioxide microspheres-supported palladium catalyst (Pd/TiO₂-350) was prepared and characterized using BET, XRD, XPS, SEM, EDX, and TEM analyses. An ICP-OES analysis of Pd/TiO₂-350 further confirmed the successful Pd immobilization on TiO₂ with a palladium loading of 0.1 mmol g^?1. Pd/TiO₂-350 efficiently catalyzed the Suzuki-Miyaura reaction of aryl iodides with arylboronic acids to give the corresponding biaryl derivatives in good to excellent yields. After the reaction, the catalyst was recovered by centrifugation and reused three times without significant loss of its catalytic activity. Moreover, the loading of palladium species further decreased to 0.001 mol%, and the total turnover number and turnover frequency of the catalyst reached as high as 99 000 and 0.57 s^?1, respectively.     

Practical synthesis of biaryl colchicinoids containing 3,4-catechol ether-based A-rings via Suzuki cross-coupling with ligandless palladium in water

Eight new biaryl colchicinoids containing 3^′,4^′-methylene or benzodioxy ether bridges were synthesized. The key synthetic step employed a ligandless, aqueous Suzuki cross-coupling reaction catalyzed by Pd(OAc)₂ with tetrabutylammonium bromide (TBAB) and potassium carbonate (K₂CO₃). The biaryl Suzuki products were typically formed in 5-30 min and always in less than 1 h.     

Transition‐Metal‐Free Reaction of Aryltrimethylammonium Iodides with Arylzinc Reagents

Reaction of aryltrimethylammonium iodides with arylzinc chlorides in the absence of a transition‐metal catalyst to form biaryl compounds was performed under mild conditions. The reaction was suitable for a broad scope of substrates and exhibited good compatibility of functional groups. The Mg²⁺ ion was demonstrated to markedly promote the reaction.     

Hiyama cross‐coupling reaction using Pd(II) nanocatalyst immobilized on the surface of Fe3O4@SiO2

We report a simple process for the synthesis of Fe₃O₄@SiO₂/APTMS (APTMS = 3‐aminopropyltrimethoxysilane) core–shell nanocatalyst support. The new nanocatalyst was prepared by stabilization of Pd(cdha)₂ (cdha = bis(2‐chloro‐3,4‐dihydroxyacetophenone)) on the surface of the Fe₃O₄@SiO₂/APTMS support. The structure and composition of this catalyst were characterized using various techniques. An efficient method was developed for the synthesis of a wide variety of biaryl compounds via fluoride‐free Hiyama cross‐coupling reactions of aryl halides with arylsiloxane, with Fe₃O₄@SiO₂/APTMS/Pd(cdha)₂ as the catalyst under reaction conditions. This methodology can be performed at 100°C through a simple one‐pot operation using in situ generated palladium nanoparticles. High catalytic activity, quick separation of catalyst from products using an external magnetic field and use of water as green solvent are attributes of this protocol.     

纳米Cu2O催化二苯甲烷二氨基甲酸苯酯无溶剂热分解制备二苯甲烷二异氰酸酯

研究了无溶剂条件下纳米Cu₂O催化二苯甲烷二氨基甲酸苯酯(MDPC)热分解制备二苯甲烷二异氰酸酯(MDI),考察了纳米Cu₂O的制备条件与反应条件对MDPC热分解反应性能的影响.结果表明,水解法制备的纳米Cu₂O在Ar中于300℃焙烧2h,其催化性能最佳;最佳的反应条件为Cu₂O用量为原料总重的0.06%,反应温度220℃,反应压力0.6kPa,反应时间12min,此时MDPC转化率达到99.8%,MDI选择性86.2%.     

Formation of sulfur surface species on a commercial NO<Subscript>x</Subscript>-storage reduction catalyst

The influence of SO₂ exposure under lean (oxidizing) and rich (reducing) reaction conditions on the storage and oxidation/reduction function of a commercial NO_x storage-reduction catalyst was investigated by temperature-programmed uptake experiments and high temperature XRD. Both the storage capacity and the oxidation/reduction function of the catalyst were deactivated by SO₂ exposure under lean and rich reaction conditions. The deactivation of the storage component, i.e. the loss of the NO_x storage capacity, resulted mainly from the formation of Ba-sulfates accumulating in the bulk phase, which have a high thermal stability (>800°C) and, therefore, cannot be removed under the typical operation conditions of a NSR catalyst. For the oxidation function only a temporarily deactivation during lean reaction conditions was observed. Besides the formation of SO^2- ₄ species on the storage component at the beginning of the SO₂ exposure under rich conditions, an adsorption of SO₂ on the noble metal component was observed resulting in the formation of sulfur deposits. The oxidation of these sulfur species with a subsequent spillover of SO^2- ₄ species to the storage component during lean conditions could accelerate the deactivation of the storage capacity.     

费托合成CeO2助Co/SiO2催化剂的失活

在固定床反应器上考察了原粒度(1～3mm)CeO2助Co/SiO2催化剂的费托反应性能,提出了催化剂失活的机理,并采用程序升温还原、X射线衍射和X射线光电子能谱对催化剂进行了表征.结果表明,在1.5MPa,488K和400h-1条件下进行的300h稳定性实验中,原粒度CeO2助Co/SiO2催化剂上的CO平均转化率达到41%,液态烃选择性达到85%,液态烃中C10 烃的质量含量占88%以上.反应器出口的催化剂中有少量的CoO和Co2SiO4生成.催化剂的失活过程受动力学控制而非热力学控制,催化剂的失活机理为:高分散的纳米Co离子在反应器出口高水蒸气压力的作用下,以CoO为中间物种,与水合SiO2作用生成Co2SiO4,即Co H2O→CoO H2,SiO2 H2O→OSi(OH)2,2CoO OSi(OH)2→Co2SiO4 H2O.     

Reaction Kinetics and Mechanism of Selective NO Reduction on a CoZSM-5 Catalyst as Studied by SSITKA

The dynamics of ¹³C transfer from methane to carbon dioxide was studied under the steady-state reaction conditions of selective NO reduction with methane on a CoZSM-5 catalyst at various reactant (NO, CH₄, and O₂) concentrations and temperatures. It was found that the reaction occurs by a two-pathway mechanism with the participation of Co²⁺ sites (or CoO _x clusters) and paired Co²⁺–OH sites localized at the boundary between the clusters and the zeolite; in this case, the rate of the reaction at boundary sites was higher by more than one order of magnitude. Based on the numerical simulation of isotopic response curves, the concentrations of intermediate compounds and the rate constants of particular steps were evaluated; differences in the kinetics via the above reaction pathways were found and analyzed.     

Methanol aided synthesis of PdNPs decorated on montmorillonite K 10 and its implication in Suzuki Miyaura type cross coupling reaction under base free condition

An efficient catalyst PdNPs decorated on Montmorillonite K 10 is prepared by simply stirring Pd(OAc)₂ in methanol at room temperature without using any external reducing agent. The catalyst shows excellent activity for Suzuki Miyaura type cross coupling reaction between aryl diazonium salt and arylboronic acid under ligand and base free reaction conditions within short reaction time. The main advantage of this methodology is the easy synthesis of heterogeneous PdNPs @ Mont K 10 catalyst in a mild condition without using any reducing agent or additive and the catalyst is very efficient for biaryl synthesis. The catalyst is well characterized by SEM, EDX, TEM, BET, Powder XRD, TGA, DSC etc. The reaction pathway is greener with aqueous reaction medium, base free reaction condition, room temperature and reusable heterogeneous catalyst.     

Synthesis of Novel Triazole Incorporated Thiazolone Motifs Having Promising Antityrosinase Activity through Green Nanocatalyst CuI-Fe3O4@SiO2 (TMS-EDTA)

In the present work, novel 5-((1-benzyl-1,2,3-triazol-4-yl)methoxybenzylidene)-2-(arylamino)thiazol-4-one thiazolone incorporated triazole derivatives have been designed as tyrosinase inhibitors. The compounds were synthesized through click reaction in good yield. Moreover, the antityrosinas activity of the synthesized derivatives was evaluated. In the search for establishing a click copper-catalyzed azide/alkyne cycloaddition (CuAAC) reaction under strict conditions, in terms of a novel air-stable, a recyclable and efficient magnetic catalyst was planned for new triazole derivatives as a well-organized copper iodide supported on the functionalized Fe₃O₄@SiO₂ core-shell (CuI/Fe₃O₄@SiO₂(TMS-EDTA) nanoparticles). The engineered nanocatalyst synthesized for the first time and characterized by different methods, including FT-IR spectroscopy, XRD, FESEM, EDX, TEM, TGA, and BET analysis. The excellent catalytic performance in ethanol with high surface area (351.7 m²g⁻¹) and short reaction time for diverse functional groups (120–200 min), no use of toxic solvents, reusability of the catalyst, and using eco-friendly conditions are the advantageous of this work. Moreover,the nanocatalyst can be used at least five times without any significant decrease in the yield of the reaction. The thiazolidine-triazole derivatives 9a , 9c , 9e , and 9 g showed promising tyrosinase inhibitory activity with IC₅₀ values in the range of 5.90–9.81 μM. The compounds were found to be considerably more potent tyrosinase inhibitors than the reference inhibitor kojic acid (IC₅₀ = 18.36 μM).     

Study on Electrocatalytic Oxidation of L‐Cysteine at Glassy Carbon Electrode by (FcM)TMA and Its Electrochemical Kinetics

The electrocatalytic oxidation of L ‐cysteine by (ferrocenylmethyl)trimethylammonium at a glassy carbon electrode in 0.1 M Na₂SO₄ aqueous solution has been studied. The rate constant for the catalytic reaction was evaluated as (4.28±0.05)×10³ M^?1 s^?1 by chronoamperometry. Experimental conditions, which maximize the current efficiency of the electrocatalytic oxidation, such as pH value and the concentration of the catalyst, were also investigated. The experimental results of electrocatalytic kinetics of L ‐cysteine oxidation on GCE in the presence of (ferrocenylmethyl)trimethylammonium obviously support the reaction mechanism proposed and the rate determining step assumed in scheme described in this work.     

SO42-/SnO2-硅藻土型固体酸的制备及其对正丁酸与异戊醇的催化酯化

采用质量比为1∶3的SnCl₄·5H₂O和硅藻土制备的硅藻土Sn(OH)₄溶胶,70 ℃老化12 h,90 ℃干燥12 h、3.0 mol/L硫酸浸渍3 h、550 ℃焙烧3.5 h,制备了SO₄^2-/SnO₂硅藻土型固体酸催化剂。 利用IR、 XRD、TG测试技术表征了催化剂的理化性质。 用于催化正丁酸与异戊醇的酯化反应,当n（异戊醇）∶n（正丁酸）=1.4∶1、催化剂用量为反应物总质量的2.5%、10 mL苯、反应时间70 min时,酯收率为97.7％。 结果表明,该催化剂兼具多元氧化物型固体酸和硫酸酸化改性天然粘土固体酸催化剂的优点,催化活性高,成本低廉、制备方法简单并可适当回收循环使用。     

Statistical optimization of biodiesel production from para rubber seed oil by SO3H-MCM-41 catalyst

The experimental parameters for biodiesel production from para rubber seed oil and methanol using a SO₃H-MCM-41 catalyst were optimized statistically. The SO₃H-MCM-41 catalyst was synthesized by co-condensation in the presence of tetraethyl orthosilicate, 3-mercaptopropyl (methyl) dimethoxysilane (MPMDS) and cetyl-trimethylammonium bromide. In the last step, the solid catalyst (SH-MCM41) was oxidized by H₂O₂ to SO₃H-MCM-41. The acid capacity of the obtained SO₃H-MCM-41 catalyst was quantified by back titration with 0.1 M sodium hydroxide. The physical and chemical properties of the SO₃H-MCM-41 were characterized by nitrogen adsorption/desorption, X-ray diffractometry, Fourier transform infrared spectroscopy and thermogravimetric analysis. The effect of varying the catalyst loading (wt.%), reaction time (h) and temperature (°C) and molar composition of MPMDS on the biodiesel yield were investigated using a 2^k factorial design. The optimal conditions to maximize the biodiesel yield, obtained from the response surface analysis using a Box–Behnken design, was a 14.5 wt.% catalyst loading, and a reaction time and temperature of 48 h and 129.6 °C. Under these conditions a fatty acid methyl ester (biodiesel) yield of 84% was predicted, and an 83.10 ± 0.39% yield experimentally obtained.     

Selective oxidation of alcohols with hydrogen peroxide catalyzed by tungstate ions (WO4) supported on periodic mesoporous organosilica with imidazolium frameworks (PMO-IL)

Tungstate ions supported on the periodic mesoporous organosilica with ionic liquid frameworks (WO₄⁼@PMO-IL) were found to be a recoverable catalyst system for the highly selective oxidation of various primary or secondary alcohols to the corresponding aldehydes or ketones by 30% H₂O₂ as green oxidant under neutral aqueous reaction conditions. The catalyst can be also recovered and efficiently reused in seven subsequent reaction cycles without any remarkable decreasing in the catalyst activity and selectivity. Moreover, N₂ sorption analysis, transmission electron microscopy (TEM) images, and thermal gravimetric analysis (TGA) showed that the structure regularity and functional groups loaded of the catalyst were not affected during the reaction process.     

The use of sulfated tin oxide as solid superacid catalyst for heterogeneous transesterification of <Emphasis Type="Italic">Jatropha curcas</Emphasis> oil

This work presents the use of sulfated tin oxide enhanced with SiO₂ (SO₄²⁻/SnO₂-SiO₂) as a superacid solid catalyst to produce methyl esters from Jatropha curcas oil. The study was conducted using the design of experiment (DoE), specifically a response surface methodology based on a threevariable central composite design (CCD) with α = 2. The reaction parameters in the parametric study were: reaction temperature (60°C to 180°C), reaction period (1 h to 3 h), and methanol to oil mole ratio (1: 6 to 1: 24). Production of the esters was conducted using an autoclave nitrogen pressurized reactor equipped with a thermocouple and a magnetic stirrer. The maximum methyl esters yield of 97 mass % was obtained at the reaction conditions: temperature of 180°C, reaction period of 2 h, and methanol to oil mole ratio of 1: 15. The catalyst amount and agitation speed were fixed to 3 mass % and 350–360 min⁻¹, respectively. Properties of the methyl esters obtained fell within the recommended biodiesel standards such as ASTM D6751 (ASTM, 2003).