异丙基溴化镁催化脱氧反应

格氏试剂通常以碳负离子形式对亲电试剂进行加成。但是有催化量的Cp_2TiCl_2存在时,具有β质子的烷基格氏试剂往往能发生还原反应或氢镁化反应。例如,使环氧键、碳氧双键、硅氧键、硅卤键、碳卤键、碳氮双键、碳氮三键、碳碳双键、碳碳三键等还原或氢镁化的反应已有报道。但是,对硫氧双键、氮氧键、磷氧双键和砷氧双键的     

碱金属还原反应的机理和反应介质与产物pK_a的关系

探讨了使用碱金属-质子溶剂对炔烃、共轭烯烃、芳香化合物、羰基化合物和共轭羰基化合物进行还原的反应机理,以及质子溶剂的选择和体系还原产物负离子中间体的共轭酸pKa之间的关系.     

铜络合物催化的格氏试剂不对称1,4-共轭加成反应研究进展

铜络合物催化的有机金属试剂与α,β-不饱和羰基化合物的1,4-共轭加成反应, 是形成新的C—C键的重要方法之一. 介绍了铜络合物催化的格氏试剂与α,β-不饱和羰基化合物的立体选择性1,4-共轭加成反应的研究进展.     

铑催化的串联分子内胺化/硅-碳(sp~3)键活化合成共轭硅杂环化合物

正共轭硅杂环化合物在太阳能电池、有机发光材料、荧光探针等领域都得到了广泛的关注和研究.其传统合成方法中因为往往需要计量的锂试剂或格氏试剂,官能团耐受性受到了极大的限制.近年来,包括北京大学化学与分子工程学院席振峰教授在内的一些科学家开拓的碳-硅键活化反应代表了一种构建含硅化合物的新方向.在此策略指引下,清华大学药学系何伟课题组设计了如下图所示的铑催化的串联分子内胺化/硅-碳(sp~3)键活化反应来快速高效合成共轭硅杂环化合物.研究发现,添加剂对该串联反应中关键的碳-硅键活化的化学选择性有重要的影响:在质子源(正辛醇)的作用下会发生硅-碳(sp~3)键活化得到共轭硅杂环化合物2,而在π酸(3,3-丙烯醛)存在时则发生硅-碳(sp~2)     

硝酸铈铵诱导的1,3-二羰基化合物对二烯酮和二烯酯的环加成反应

硝酸铈铵(CAN)作为一个良好的单电子氧化剂近年来在有机合成中已被广泛用于构筑各种类型的碳碳键[1].硝酸铈铵诱导的1,3-二羰基化合物对孤立双键[2]、烯醇硅醚[3]、乙烯基醚[4]、共轭双烯[5]等的环加成反应已有报道.然而对其与具有多个不饱和基团化合物的区域选择性环加成反应尚鲜见报道[6].本文报道CAN诱导的1,3-二羰基化合物1对二烯酮及二烯酯(2)的区域选择性环加成反应,结果以中等产率高区域选择性地得到了二氢呋喃类化合物3(Eq.1).可能的反应机理示于Scheme 1.     

3-羟基哌啶氮α-碳负离子的形成及α-羟烷化反应

合成了（S）-3-羟基哌啶苯硫醚化合物6作为3-羟基哌啶氮α-碳负离子手性合成子（B）的合成等效体.化合物6经羟基去质子现场保护、萘锂（LN）还原锂化形成手性哌啶醇双负离子中间体B.双负离子B可被质子淬灭得到还原产物2a 而与羰基化合物反应则得到α-羟烷化产物12～17和少量还原产物2a.该反应具有很高的环上2,3-位非对映立体选择性 与非对称的羰基化合物反应产生新手性中心的立体选择性从50：50到77：23.     

金催化选择性氧化共轭炔基炔酰胺合成4-羰基丁-2-炔酰胺（英文）

通过金催化选择性氧化1,3-共轭炔基炔酰胺,为4-羰基丁-2-炔酰胺化合物的合成提供了一种新的方法.这种含有活化的不饱和炔烃的1,4-双羰基化合物是有机化学中一种重要的合成子.利用该金催化氧化方法,可以高度选择性地对共轭炔烃的1,4-位进行氧化得到2-炔-4-羰基丁酰胺化合物,而不是生成较为常见的1,2-双羰基化合物.在该选择性氧化的条件下,可以以较高的收率得到一系列4-羰基丁-2-炔酰胺化合物.     

1,2,1′,2′-双蒽醌-3,12-二羧酸的还原反应

1,2,1＇,2＇-双蒽醌-3,12-二羧酸(1)是一个π-共轭体系芳环化合物,内环酮基由于受空间效应和共振效应的影响,不能被还原成相应的醇或相应的碳氢基团,却成了不常见的内“双氧桥”化合物(4)。化合物2,3,4的结构已经确定,并对1的还原机理进行了初步讨论。     

2-芳基-3,4-二氮杂芴酮和2-芳基-3,4-二氮杂螺二芴衍生物的合成

水合茚三酮与芳甲基酮、水合肼缩合环化制得2-芳基-3,4-二氮杂芴酮(2); 2经还原得2-芳基-3,4-二氮杂芴(3).2与2-溴联苯格氏试剂反应得到中间体叔醇(4); 4在酸性条件下关环合成了2-芳基-3,4-二氮杂螺二芴,其结构经1H NMR,13C NMR和元素分析表征.     

以汉斯酯1,4-二氢吡啶为还原剂的还原胺化反应研究

还原胺化是有机合成中的重要反应,即醛和酮在适当还原剂作用下与伯胺或仲胺制备仲、叔胺.汉斯酯1,4-二氢吡啶衍生物(HEH)作为仿生有机还原剂已被用于α,β-不饱和羰基化合物、缺电子的共轭烯烃和亚胺的选择性还原以及还原胺化等重要的有机反应中.以HEH为还原剂,7-氨基-4-甲基香豆素与常见的醛为模型来探索通过还原胺化反应标记醛类化合物的可行性,共得到16个还原胺化产物,其中13个化合物未见文献报道.     

TiO2光催化薄膜在陶瓷器具上抗菌效果的研究

抗菌薄膜;TiO2光催化薄膜在陶瓷器具上抗菌效果的研究     

Development of new glass composite membranes and their properties for low temperature H2/O2 fuel cells.

A new glass electrolyte formed by constant amounts of titanium oxide (TiO2) and various amount of phosphotungstic acid (PWA) doped P2O5-SiO2 is prepared using the sol-gel process. The structural formation is confirmed by Fourier infrared spectroscopy (FTIR) and from thermogravimetric and differential thermal analysis (TG/DTA) measurements, the glasses display good thermal stability. Further characterisation is undertaken by N2 adsorption/desorption measurements, proton conductivity and hydrogen permeability analyses and a H2/O2 fuel cell test is also performed. The glass materials with large pores and specific surface area are suitable for use as the electrolyte in H2/O2 fuel cells. The effect of TiO2 processing with constant amount of PWA in phosphosilicate glasses, is investigated and discussed. The hydrogen permeability is 1.57x10(-11) mol cm(-1) s(-1) Pa(-1) at 110 degrees C for 0.8 mm thick glass; a power density of 46.3 mW cm(-2) at 125 mA cm(-2) and a current density of 175 mA cm(-2) is obtained (T=28 degrees C, relative humidity).     

Synthesis,crystal structure and thermal properties of Na2Ti(CF3COO)6(CF3COOH)2

The compound Na₂Ti(CF₃COO)₆(CF₃COOH)₂ was synthesized as colorless crystals, extremely unstable in air, by the reaction of TiCl₄ with trifluoroacetic acid and sodium trifluoroacetate. Crystallographic studies have shown that this sodium trifluoroacetatotitanate is the first example of a tetravalent titanium carboxylate [Ti(RCOO)₆]²– containing titanium in an octahedral environment of oxygen atoms of carboxylate groups. Thermal decomposition of Na₂Ti(CF₃COO)₆(CF₃COOH)₂ in an argon atmosphere results in the complex fluoride Na₂TiF₆.     

掺Cu对MoO3-TiO2/SiO2上光促甲烷和水表面反应的影响

 在固定床环隙反应器中,借助紫外光的激发,气相甲烷和水在MoO3-TiO2/SiO2催化剂表面生成了甲醇和氢气,当在催化剂中掺杂Cu2+后,光催化剂的活性明显提高. XRD,IR,UVDRS和TPD的研究结果表明,在催化剂表面形成了具有Mo-O-Ti和Mo-O-Cu基元的高度分散物种,不但使得吸光带边明显蓝移,而且扩展了催化剂的光响应范围. 所形成的复合结构还可以优化单组分的吸光性能并促进对反应物分子的吸附活化,同时可以有效地转移光生电子和空穴. 掺杂Cu2+能够进一步延长光生电子-空穴对的寿命,进而提高反应的量子产率.     

PdO/TiO2 and Pd/TiO2 Heterostructured Nanobelts with Enhanced Photocatalytic Activity

Heterostructures play an important role not only in the manufacture of semiconductor devices, but also in the field of catalysis. Herein, we report the synthesis of PdO/TiO₂ and Pd/TiO₂ heterostructured nanobelts by means of a simple co‐precipitation method, followed by a reduction process using surface‐modified TiO₂ nanobelts as templates. The as‐obtained heterostructures were characterized by transmission electron microscopy, X‐ray photoelectron spectroscopy, and UV/Vis diffuse reflectance spectroscopy. PdO and Pd nanoparticles with a size of about 1.3 and 1.6 nm were assembled uniformly on the surface of TiO₂ nanobelts, respectively. Compared with TiO₂ nanobelts, PdO/TiO₂ and Pd/TiO₂ hybrid nanobelts exhibit enhanced photocatalytic activity upon UV and visible‐light irradiation. Photoelectrochemical technology was used to study the heterostructure effect on enhanced photocatalytic activity. Our mechanistic investigation revealed that energy‐band matching is the major factor in the observed enhancement of photocatalytic activity.     

Titanium-Promoted Rh-Mn-Li/SiO2 for C2-Oxygenates Synthesis from Syngas： Effect of Low Titanium Loading

1. Introduction There is great interest in understanding the het- erogeneous catalysis by which Rh-containing catalyst converts CO/H2 into useful organic compounds, par- ticularly C2 oxygenates such as ethanol, acetic acid and acetaldehyde with high efficiencies [1]. The addi- tion of appropriate promoters can enhance the rate of formation of these oxygenates. Many elements have been tested as promoters over rhodium-based cata- lysts, including compounds of alkali [2], rare earth [3], and tr…     

Products of lithium interaction with nanostructured oxides SnO2-TiO2 and mechanism of charge-discharge of electrodes in a lithium-ion battery

Products of lithium interaction with thin-film nanostructured SnO₂-TiO₂ (ST) oxides are studied with the aid of x-ray diffraction analysis and Moessbauer spectroscopy on the ¹¹⁹Sn nuclei. Electrochemical properties of a series of the ST electrodes with different concentrations of TiO₂ varied from 0 to 20 mol % are also examined. It is concluded that the specific feature of the charge-discharge mechanism of the ST electrodes is a significant participation of oxygen in reversible reactions during insertion and extraction of lithium as compared with an alloying mechanism of operation of tin-containing anodes. The leading role in this is played by titanium oxide. Remaining stable towards reduction by lithium, it facilitates the holding of the neighboring layers of SnO₂ in a nanodisperse state and in an oxidized state. The effect of a decrease in the capacity degradation in modified TiO₂ electrodes, which is discovered in this work, is attributed to the hampering of the growth of nanocrystallites of β-Sn by interlayers of tin and titanium oxides mentioned above.     

染料在纳米TiO2薄膜表面吸附性能的研究

采用溶胶－凝胶法制备纳米TiO2薄膜，并通过吸附染料形成染料／TiO2复合薄膜。分析了染料与TiO2薄膜的相互关系，利用紫外可见、比表面等技术研究染料在纳米TiO2薄膜表面的吸附性能，并计算出TiO2薄膜对染料的最大吸附率。研究表明，染料溶液浓度、温度以及TiO2薄膜浸泡时间对染料吸附量有着显著的影响，染料的吸附性能直接影响着太阳能电池的光电转换效率。     

TiO2-CeO2介孔复合氧化物的合成及应用

以氯化十六烷基吡啶(C16PyCl)为模板剂, 在室温、中性条件下合成了TiO2-CeO2介孔复合氧化物, 分别用红外光谱(FT-IR)、X射线粉末衍射(XRD)和BET 比表面测定等技术对介孔TiO2的结构、晶相和比表面积进行了表征. 结果表明, Ce4+的引入能稳定介孔结构. 负载活性组分Ru 后, Ru 颗粒与介孔复合载体发生相互作用, 尽管可能会部分堵塞孔道, 但对于甲醇分解为CO 和H2, Ru/m-TiO2-CeO2的催化活性依然远高于Ru/m-TiO2. Ru 和CeO2之间的相互作用对甲醇分解反应表现出协同效应.     

半导体复合CdS/TiO2催化剂改性及冷冻-光催化组合方法应用的初步研究

采用溶胶-凝胶法制备多孔氧化钛,并耦合CdS,制备多孔耦合CdS/TiO₂催化剂.煅烧温度为700℃,CdS掺杂比例为3%时,催化剂性能较优.以太阳光为光源,考查了溴氨酸初始浓度对其降解效果的影响,并采用冷冻-光催化组合方法对较高浓度的溴氨酸废水的处理进行了初步研究.浓度为500 mg/L的溴氨酸模拟废水(其中氯化钠质量浓度为500 mg/L)经冷冻后,当成冰率为70%时,体系中冰层的Na⁺含量、总有机碳(TOC)和吸光度分别由209.88 mg/L,208.90 mg/L和8.120降至19.06 mg/L,24.80 mg/L和0.638.使用多孔耦合催化剂对该冰层融水光降解,光照6 h,褪色率和TOC去除率分别达到100%和87.04%.