高分子载体Lewis酸催化剂——聚苯乙烯-三氯化铝/四氯化锡复合物

聚苯乙烯交联白球在氯仿中与三氯化铝和四氯化锡等摩尔混合物反应,制成了一种相当稳定的高分子载体双金属系Lewis酸复合物。该复合物对酯化、缩醛、缩酮、成醚等有机反应具有良好的催化效能,并可重复使用多次。     

Sulfuric Acid Adsorbed on Silica Gel. A Multipurpose Acid Catalyst

A series of acid catalyzed reactions like the dehydration of alcohols, conversion of ketones to 1,3-dioxolanes and their hydrolysis, α,β-unsaturated ketones to enol ethers, and alcohols to methyl-methoxyethyl ethers are performed efficiently in high yield with sulfuric acid adsorbed on silica gel as catalyst.     

Silica Supported Catalysis: A Practical use of an Iron Lewis Acid

The silica-supported iron Lewis acid [(η⁵-C₅H₅)Fe(CO)₂(THF)]⁺ [BF₄]⁺ (1), was found to catalyze the formation of an enol ester, cyclopropane, or aziridine from a diazo compound and an aldehyde, olefin, or imine, respectively. Unlike the non silica-supported iron Lewis acid, the catalyst is recoverable and reusable.     

Synthesis of Carbamates Using Yttria-Zirconia Based Lewis Acid Catalyst

Abstract

A variety of amines react with chloroformates in the presence of catalytic amount of yttria-zirconia based catalyst to afford the corresponding carbamates in excellent yields.     

Preparation and Acid Catalytic Activity of TiO2 Grafted Silica MCM-41 with Sulfate Treatment

TiO2 grafted silica MCM-41 catalyst with and without sulfate treatment were prepared. The structural and acid properties of these materials were investigated by XRD, N2 adsorption-desorption, element analysis, thermal analysis, Raman and FTIR measurements. Their acid-catalytic activities were evaluated using the cyclization reaction of pseudoionone. It was found that the obtained materials possess well-ordered mesostructure, and the grafted TiO2 components were in highly dispersed amorphous form. T/MCM41 without sulfation contained only Lewis acid sites, while Br?nsted and Lewis acidities were remarkably improved for the sulfated materials ST/MCM41 and d-ST/MCM41. T/MCM-41 was not active for the cyclization reaction of pseudoionone, but ST/MCM-41 and d-ST/MCM-41 possessed favorable catalytic activities. The catalytic performance of ST/MCM-41 was comparable with that of the commercial solid acid catalyst of Amberlyst-15, and better than that of d-ST/MCM-41, although the latter underwent a second TiO2 grafting process and accordingly had higher Ti and S content. The specific surface structure of Si-O-Ti-O-S=O in ST/MCM-41 and the bilateral induction effect of Si and S=O on Si-O-Ti bonds were speculated to account for its higher acid catalytic activity.     

碘作为Lewis酸催化剂在合成中的应用

碘催化的有机反应具有价廉易得、操作简单、温和、清洁、高效及高选择性等优点, 广泛应用于亲电反应、亲核反应、多组份反应以及其它涉及复杂官能团化合物的合成反应中, 在环境友好化学合成、复杂化合物合成及选择性合成领域具有应用价值.     

A Rapid Access to Novel and Known Benzimidazole Derivatives Using Silica Chloride as a Reusable Catalyst

A new application of silica chloride as an easily available and reusable solid acid catalyst for the synthesis of benzimidazole and its derivatives through the condensation of o‐phenylenediamines and orthoesters under thermal and solvent‐free conditions is described. This novel and eco‐friendly method is very cheap and has many advantages including excellent yields, short reaction time, and simple work‐up procedure.     

Ruthenium Bisphosphine Catalyst on Functionalized Silica： Novel Efficient Catalyst for Carbon Dioxide Hydrogenation to Formic Acid

Catalytic hydrogenation of carbon dioxide to valuable chemicals and fuels has gainedmuch attention recently in view of the abundant availability and the greenhouse effect ofCO2. CO2 hydrogenation to formic acid is an economic reaction, but it is alsotherm…     

Lewis Acid Catalyzed Transfer Hydromethallylation for the Construction of Quaternary Carbon Centers

The design and gram‐scale synthesis of a cyclohexa‐1,4‐diene‐based surrogate of isobutene gas is reported. Using the highly electron‐deficient Lewis acid B(C₆F₅)₃, application of this surrogate in the hydromethallylation of electron‐rich styrene derivatives provided sterically congested quaternary carbon centers. The reaction proceeds by C(sp³)?C(sp³) bond formation at a tertiary carbenium ion that is generated by alkene protonation. The possibility of two concurrent mechanisms is proposed on the basis of mechanistic experiments using a deuterated surrogate.     

一种新的高分子Lewis酸催化剂的制备及其催化活性的研究

本文研究了高分子催化剂CPVC-FeCl_3在酯化、酯交换、缩醛或缩酮的合成及呐 重排反应中的应用。本催化剂具有操作简便、无腐蚀性,催化剂易从反应混合物中分离、并能重复使用等优点。     

碘作为Lewis酸催化剂在合成中的应用进展

碘催化的有机反应具有价廉易得、操作简单、温和、清洁、高效及高选择性等优点,广泛应用于亲电反应、亲核反应、多组份反应以及其它涉及复杂官能团化合物的合成反应中,在环境友好化学合成、复杂化合物合成及选择性合成领域具有应用价值.     

Chiral Phosphine Ligands with Amino Acid Moieties

Abstract

Amino acids containing functionalized aromatic substituents are of considerable interest as building blocks for the syntheses and the design of new types of proteins and pharmacologically active compounds. In contrast to amino acids bearing phosphonated phenyl substituents [1], phosphinophenyl derivatives have been reported only very recently[2]. We have been able to synthesize phosphinophenyl amino acids of type 1 or 2 by nucleophilic phosphination [3] of the potassium salts of 2-and 4-fluoro-a-phenylglycine and-alanine with potassium phosphides Ph(R')PK in high yields.     

高分子载体Lewis酸催化剂:聚苯乙烯、三氯化铝/四氯化钛复合物

聚苯乙烯交联白球与等摩尔的AlCL₃和TiCl₄混合物在CS₂中反应,可制得一种十分稳定的高分子-双金属盐复合物。此复合物含氧量为11.4％,Al/Ti=2/1。它在丙酮水溶液中显强酸性,且约在2小时接近平衡酸度值。紫外及红外分析证实了聚苯乙烯与AlCl₃/DiCl₄之间复合物的形成。     

Novel Basic Ionic Liquid Based on Alkylammonium as Efficient Catalyst for Knoevenagel Reaction

The typical Knoevenagel condensation was carried out smoothly in the presence of a basic ionic liquid of N,N,N′,N′-tetramethyl-N′-hexyl-ethylenediammonium tetrafluoroborate ([TMHEDA]BF₄), and 99% of yield was obtained using ethyl cyanoacetate and benzaldehyde as substrates at 60 °C for 1 h. Four reuses of the ionic liquid without dramatic decrease in catalytic activity for Knoevenagel condensation demonstrated the good stability and operability of the ionic liquid. Moreover, the typical nucleophilic addition reactions were also accomplished by the same ionic liquid to check its feasibility. The dual function of the basic ionic liquid both as solvent and catalyst, combined with simple product separation and recycling, is expected to contribute to the development of a green and environmentally friendly strategy.     

表面含磺酸基的介孔分子筛催化剂SBA-15-SO3H的制备及其催化性能

采用直接和后合成两种方法制备出含磺酸基的介孔分子筛SBA-15-SO₃H,用XRD和红外光谱分析制备过程中催化剂结构和组成的变化.结果表明,两种方法制备出的含磺酸基的催化剂都保持了SBA-15分子筛的完整晶体结构,并含有质子酸中心-SO₃H;固体核磁共振表征结果证明,两种方法都使MPTMS存在于分子筛的表面;用N₂吸附-脱附测定了它们的比表面积、孔径和孔容;TGA分析认为,MPTMS在分子筛表面的热稳定性大于300℃,酸碱滴定结果说明,直接法获得的催化剂的酸中心多于后合成法.酯化反应结果表明,直接法合成的催化剂比后合成法具有更高的稳定性,且简便、快捷、高效.     

Scandium Trifluoromethanesulfonate as an Extremely Active Lewis Acid Catalyst in Acylation of Alcohols with Acid Anhydrides and Mixed Anhydrides

Scandium trifluoromethanesulfonate (triflate), which is commercially available, is a practical and useful Lewis acid catalyst for acylation of alcohols with acid anhydrides or the esterification of alcohols by carboxylic acids in the presence of p-nitrobenzoic anhydrides. The remarkably high catalytic activity of scandium triflate can be used for assisting the acylation by acid anhydrides of not only primary alcohols but also sterically-hindered secondary or tertiary alcohols. The method presented is especially effective for selective macrolactonization of omega-hydroxy carboxylic acids.