The use of Nafion-H® as an efficient catalyst for the direct conversion of primary and secondary trimethylsilyl ethers to their corresponding ethers under mild and heterogeneous conditions

Primary and secondary trimethylsilyl ethers were converted to their corresponding ethers in the presence Nafion-H® with good to excellent yields under mild and heterogeneous conditions.     

Novel metathesis catalysts based on ruthenium 1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidenes: synthesis, structure, immobilization, and catalytic activity

The synthesis of novel ruthenium-based metathesis catalysts containing the saturated 1,3-bis(2,4,6-trimethylphenyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene ligand, that is, [RuCl2(NHC)[=CH-2-(2-PrO)-5-NO(2)-C6H3]] (1) and [Ru(CF3COO)2(NHC)[=CH-2-(2-PrO)-5-NO2-C6H3]] (2) (NHC=1,3-bis(2,4,6-trimethylphenyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene) is described. Both catalysts are highly active in ring-closing metathesis (RCM) and ring-opening cross-metathesis (ROCM). Compound 1 shows moderate activity in enyne metathesis. Compound 2 is not applicable to enyne metathesis since it shows high activity in the cyclopolymerization of diethyl dipropargylmalonate (DEDPM). Poly(DEDPM) prepared by the action of 2 consists of 95% five-membered rings, that is, poly(cyclopent-1-enevinylene)s, and 5 % of six-membered rings, that is, poly(cyclohex-1-ene-3-methylidene)s. The polymerization proceeds in a nonliving manner and results in polyenes with broad polydispersities (1.9< or =PDI< or =2.3). Supported analogues of 2 were prepared by immobilization on hydroxymethyl-Merrifield resin and a monolithic support derived from ring-opening-metathesis polymerization (ROMP). Catalyst loadings of 1 and 2.5%, respectively, were obtained. Both supported versions of 2 showed excellent reactivity. With 0.24-2% of the supported catalysts, yields in RCM and ROCM were in the range of 76-100%. Leaching of ruthenium was low and resulted in Ru contaminations of the products of less than 0.000014% (0.14 ppm).     

Synthesis of phthalide derivatives using nickel-catalyzed cyclization of o-haloesters with aldehydes

The reaction of o-bromobenzoate (1 b) with benzaldehyde (2 a) in the presence of [NiBr(2)(dppe)] (dppe=1,2-bis(diphenylphosphino)ethane) and zinc powder in THF (24 hours, reflux temperature), afforded 3-phenyl-3H-isobenzofuran-1-one (3 a) in an 86 % yield. Similarly, o-iodobenzoate reacts with 2 a to give 3 a, but in a lower yield (50 %). A series of substituted aromatic and aliphatic aldehydes (2 b, 4-MeC(6)H(4)CHO; 2 c, 4-MeOC(6)H(4)CHO; 2 d, 3-MeOC(6)H(4)CHO; 2 e, 2-MeOC(6)H(4)CHO; 2 f, 4-CNC(6)H(4)CHO; 2 g, 4-(Me)(3)CC(6)H(4)CHO; 2 h, 4-C(6)H(5)C(6)H(4)CHO; 2 i, 4-ClC(6)H(4)CHO; 2 j, 4-CF(3)C(6)H(4)CHO; 2 k, CH(3)(CH(2))(5)CHO; 2 l, CH(3)(CH(2))(2)CHO) also underwent cyclization with o-bromobenzoate (1 b) producing the corresponding phthalide derivatives in moderate to excellent yields and with high chemoselectivity. Like 1 b, methyl 2-bromo-4,5-dimethoxybenzoate (1 c) reacts with tolualdehyde (2 b) to give the corresponding substituted phthalide 3 m in a 71 % yield. The methodology can be further applied to the synthesis of six-membered lactones. The reaction of methyl 2-(2-bromophenyl)acetate (1 d) with benzaldehyde under similar reaction conditions afforded six-membered lactone 3 o in a 68 % yield. A possible catalytic mechanism for this cyclization is also proposed.     

芳香族化合物的脱芳构化反应

芳香族化合物稳定、易得，通过芳香族化合物的脱芳构化反应，制备官能化的脂肪六元碳环化合物，早以引起人们的广泛兴趣。本文对六类脱芳构化反应进行了逐一评述，其包括：氧化脱芳构化反应；还原脱芳构化反应；光催化脱芳构化反应；亲核加成脱芳构化反应；σ-键迁移重排脱芳构化反应；过渡金属参与的脱芳构化反应。其中，过渡金属参与的脱芳构化反应，反应条件温和，反应底物广泛，可应用于生物活性物质的合成。     

Enhanced photocatalytic activity of zeolite-encapsulated TiO2 clusters by complexation with organic additives and N-doping.

In the literature it was found that titanium oxide clusters of a few metal atoms encapsulated inside the micropores of zeolite Y exhibit large blue shifts in the Ti-O ligand-to-metal charge-transfer band as compared to non-encapsulated bulk titanium dioxide particles. This blue shift of the Ti-O absorption band is believed to have a negative effect on the photocatalytic activity of zeolite-encapsulated TiO2. We report here on circumventing this problem and increasing visible-light absorption by means of a red shift of the absorption band caused by addition of some organic molecular modifiers containing acidic OH groups that can strongly bind with titanol groups TiOH. In the studied series of zeolite-encapsulated TiO2 samples, the red shift of the optical spectrum follows the order: catechol > 4-aminobenzoic acid > benzoic acid. Also N-doping of zeolite-encapsulated TiO2 clusters by thermal treatment with urea leads to a red shift of the TiO2 absorption band that depends on the annealing and hydration conditions. By comparison to the degradation of phenol in aqueous solution, we have demonstrated that these changes in the absorption spectrum on addition of the organic modifier are also reflected in the photocatalytic activity of the samples; a greater increase in photocatalytic activity (about 30%) was observed for the additive catechol.     

Dicyano-Functionalized MCM-41-Supported Palladium Complex as An Efficient Catalyst for Allylation of Aldehydes and Ketones

Dicyano-functionalized MCM-41-supported palladium complex was prepared from dicyano-functionalized MCM-41 and palladium chloride. This complex exhibited high catalytic activity in the allylation of aldehydes and ketones with allylic chlorides in the presence of SnCl2. This polymeric palladium complex can be recovered and reused without noticeable loss of activity.     

纳米级金膜微电极的制作,表征及异相催化反应

报道了纳米级金膜微电极的制作方法，用ＸＰＳ及ＳＥＭ对电极表面进行了表征，考察了该电极的循环伏安及计时电流特性，在聚吡咯修饰微带金电极上成功地实现了葡萄糖氧化酶和电子传递媒体Ｆｅ（ＣＮ）６＾３－的同时固定，并研究了ＧＯＤ／Ｆｅ（ＣＮ）６＾３－／ＰＰｙ微酶电极对葡萄糖的响应，稳态响应电流与葡萄糖浓度之间存在Ｍｉｃｈｅａｌｉｓ－Ｍｅｎｔｅｎ动力学特征。     

金属离子掺杂对TiO2光催化性能的影响

TiO₂光催化反应过程涉及光生电荷、电荷迁移、电荷在TiO₂表面的反应和溶液体相反应4个顺序相接并相互影响的步骤.在TiO₂中掺杂金属离子对以上4个步骤均有重要影响,合理的掺杂可有效地提高其光催化性能.本文综合了国内外此方面的最新研究成果,从提高TiO₂光催化性能和优化光催化反应的角度出发,在材料吸光能力、电荷扩散、表面反应、粒径和晶型等方面,全面地分析总结了金属离子掺杂的影响效果和规律性认识,并对TiO₂基光催化材料的金属离子掺杂改性研究的未来发展方向提出了建议.文中还简要介绍了相关的掺杂方法和材料表征手段.     

New Advances in Catalytic Systems for Conversion of CH_4 and CO_2

One of the main goals for developing the C1 chemical industry is the direct conversion of methane and carbon dioxide to useful products. To realize this goal, researches on new catalytic systems are being globally focused. The exploration has been evolved from traditional heterogeneous catalysis into homogeneous catalysis. Coordinate complexes, biochemical and bionics, and photo- and electrochemical catalysis have been extensively studied in recent years. Tests in laboratories have verified for the direct conversion of CH4 to CH3OH that single-pass converstion of CH4 can reach over 70% in both Hg(II) salt and Pt(II) complex systems. The main problem of these systems is the obstacles involving reaction kinetics, so they must be solved before moving to pilot tests. Other catalytic systems discussed in the present article include explorations in the early stage. Among them, features of photo and enzymatic catalyst systems, such as mild reaction conditions, better selectivity and environmentally friendliness     

稀土-沸石-TiO2三元体系光催化材料的性能研究

以钛酸丁酯、稀土硝酸盐、斜发沸石为主要原料,用溶胶-凝胶法制备了稀土-沸石-TiO2三元体系的光催化剂.使用IR,TG-DSC,XRD,SEM等手段对样品进行了表征; 以甲基橙为目标物,太阳光为光源,用光解率对光催化剂性能进行了评价.实验表明,随着沸石负载TiO2量的增加,光催化剂的3 h光解率也逐渐提高; 反应体系的温度越高,光解率越大; 当溶液pH约等于5时,光解率达到最大.