铜催化α-重氮酮对硼氢键的不对称插入反应

手性有机硼化合物在有机合成、医药、材料等诸多领域中有广泛的应用,发展该类化合物的高效合成方法一直广受关注.此前,我们发展了过渡金属催化卡宾对硼氢键(B—H)的插入反应,并实现了α-重氮酯对B—H键的不对称插入反应.本文以手性螺环双噁唑啉配体和铜的络合物作为催化剂,首次实现了α-重氮酮对膦-硼烷加合物的B—H键不对称插入反应,获得了较高的收率和高达83%ee的对映选择性.该研究成果是为数不多的以α-重氮酮作为卡宾前体的不对称杂原子氢键插入反应,为手性α-硼取代酮化合物这类新的有机硼化合物的合成提供了有效方法.     

L-脯氨酸衍生的手性N,P-配体的合成及其在不对称1,3-偶极环加成反应中的应用

从L-脯氨酸衍生而来的酰胺膦类化合物1,经脱去保护基得到的氨基膦2,用正丁基锂处理后,用2-甲氧基吡啶类化合物捕获,得到一类吡啶型的手性N,P-配体4;氨基醇与碳酸二乙酯生成的噁唑啉酮6,与四氟硼酸三乙氧基鎓盐反应制得的乙氧基噁唑啉7直接与氨基膦2反应,合成了噁唑啉型手性N,P-配体8.将两类手性N,P-配体应用于Ag(I)催化的1,3-偶极环加成反应,通过对反应条件进行优化,发现手性N,P-配体与AgOTf所形成的催化剂能很好地催化1,3-偶极环加成反应,最高可以以93%的收率获得环加成产物,ee值最高可以达到15%.     

轴不安定性联苯类膦-噁唑啉配体/铱配合物在亚胺不对称氢化反应中的应用

考察了一系列轴不安定性联苯类膦-噁唑啉配体/铱配合物作为手性催化剂用于亚胺类底物的不对称催化氢化反应.结果表明该类催化剂具有很高的催化活性(99%转化率)和较好的对映选择性(75%ee).     

面手性二芳基膦-噁唑啉配体的开发及其在不对称催化反应中的应用

膦-噁唑啉配体形成的催化剂具有出色的催化活性和对映选择性, 被广泛应用于各种不对称催化反应中. 具有面手性的膦-噁唑啉配体是其中重要的一类. 综述了面手性二芳基膦-噁唑啉配体的开发, 并按反应类型介绍了它们在不对称催化反应中的应用.     

通过不对称多组分反应高效构建手性磺酰胺类化合物

手性磺酰胺类化合物在新型药物方面研究中占据越来越重要的地位.我们成功地实现了磺酰胺、芳基重氮乙酸酯以及亚胺的不对称三组分反应.此反应给出了高达85%产率,以及优异的非对映选择性（d.r.>20：1）和对映选择性（最高可达99%ee）,为高效构建具有两个手性碳的光学纯磺酰胺类化合物提供了一种快速合成方法.我们将反应放大到了克级规模,并对三组分产物进一步衍生得到一种具有三个手性中心的光学纯含亚砜亚胺骨架的五元环化合物.反应的选择性通过过渡金属与手性磷酸协同催化控制.     

三氟甲磺酸镱催化合成噁唑啉环取代酚(胺)及相关化合物

噁唑啉环取代酚是一类重要的有机杂环类化合物,在配位化学[1]、不对称合成[2]、天然产品化学[3]及作为配体在对映选择性催化剂[1]中均有一定的应用。它们的制备方法已有所报道,例如:(1)酚酯与氨基醇的高温反应[4];(2)2-羟基-N-(2-羟乙基)-苯甲酰胺在SOC l2介质中的环化反应[3];     

手性磷酰胺配体不对称催化二芳基甲醇类化合物的合成

为了获得具有重要生理活性的手性二芳基甲醇类化合物,以R,R-1,2-环己二胺为原料获得了一系列磷酰胺配体,并系统考察了该类配体在芳基烷基锌对芳香醛的不对称加成反应中的催化活性,在优化的反应条件下,即在30mol%磷酰胺配体N-((1R,2R)-2-(异丙基氨基)环己基)-P,P-二苯基磷酰胺(9c)存在下,可以高达94%的ee值(对映体过量值)及大于90%收率获得相应的手性二芳基甲醇类化合物.尽管催化剂用量较大,在该体系中,配体可非常方便回收再利用.同时,对反应机理进行了推测,认为反应过程所形成的四元过渡态和六元过渡态,有利于提高反应的对映选择性.     

聚合物支载噁唑类化合物在不对称反应中的应用

聚合物支载噁唑类化合物主要包括聚合物支载噁唑烷酮、噁唑啉和硼杂噁唑啉等,其在不对称反应中主要用作手性助剂、手性催化剂及催化剂配体.由于其便于分离提纯、可以回收重复使用且立体选择性没有明显降低等优点在不对称反应中得到了广泛的应用.综述了近年来聚合物支载的噁唑类化合物在不对称反应中的应用     

聚合物支载噁唑类化合物在不对称反应中的应用

聚合物支载噁唑类化合物主要包括聚合物支载噁唑烷酮﹑噁唑啉和硼杂噁唑啉等, 其在不对称反应中主要用作手性助剂﹑手性催化剂及催化剂配体. 由于其便于分离提纯﹑可以回收重复使用且立体选择性没有明显降低等优点在不对称反应中得到了广泛的应用. 综述了近年来聚合物支载的噁唑类化合物在不对称反应中的应用.     

在不对称氮杂环丙烷化中双噁唑啉配位空间大小对对映选择性的影响

手性双噁唑啉是在不对称催化中广泛应用的一类重要的配体. 合成了一系列具有刚性骨架和不同配位空间的手性双噁唑啉配体, 并研究了在不对称氮杂环丙烷化反应中对对映选择性的影响, 结果表明通过调节配位空间的大小不仅可以改变对映选择性, 甚至还可以彻底改变对映面选择性. 研究结果还表明除通过改变配体手性中心的构型, 调节配体配位空间也可以改变催化剂的对映面选择性.     

Synergistic Ag(I)/nBu4NBr-catalyzed fixation of CO2 to β-oxopropyl carbonates via propargylic alcohols and monohydric alcohols

Chemical fixation of carbon dioxide under mild reaction conditions e.g. atmospheric pressure and low temperature depends upon the ability of catalyst. Herein, a synergistic catalytic scheme of silver sulfadiazine/ⁿBu₄NBr was described for the three-component reaction of propargylic alcohols, CO₂, and monohydric alcohols. This catalytic system was demonstrated effectively to provide β-oxopropyl carbonates in excellent yields (up to 99% yield with 5?mol% catalyst). The method tolerated a wide scope of propargylic alcohols and monohydric alcohols under atmospheric CO₂ pressure and solvent-free conditions. The excellent catalytic performance was attributed to the synergistic catalysis confirmed by the careful experiments.     

The role played by an iodine-containing promoter in the formation of active polycrystalline silver catalyst surface

The programmed temperature desorption method was used to study the interaction of oxygen with the surface of a polycrystalline silver catalyst promoted with iodine. Ethyl iodide almost did not interact with the unoxidized surface of silver. The adsorption of C₂H₅I on the oxidized catalyst surface resulted in the formation of two adsorbed iodine forms, silver iodide and iodine deeply dissolved in subsurface silver crystal lattice layers. The character of oxygen adsorption from the iodine-containing surface of the catalyst was determined by the amount and form of adsorbed iodine. In the presence of a iodine-containing promoter, the concentration of oxide-like oxygen sharply decreased, and the amount of strongly bound atomically adsorbed oxygen responsible for the selective transformation of ethylene glycol into glyoxal increased.     

Acid and catalytic properties of MnOm?ZrO2 (M=Ca, Ba, Sm, Yb) compositions

The volume stages of ethylene glycol oxidation to glyoxal on silver have been studied by varying the catalyst grain size. Temperature oscillations have been detected in the catalyst layer. The nature of the oscillations and the range of their generation were investigated by varying the oxygen, ethylene glycol and water vapor contents in the reaction mixture. Glyoxal formation was shown to occur on the silver catalyst surface. The generation of oscillations is responsible for the CO to CO₂ oxidation in the volume between the catalyst grains.     

铁、钴或镍助剂促进的 Ag/SiO2 催化剂上气相催化合成 3-甲基吲哚

 将铁、钴或镍促进的 Ag/SiO2 催化剂用于苯胺和 1,2-丙二醇气相催化合成 3-甲基吲哚的反应中, 并采用 X 射线衍射、H2-程序升温还原和热重分析等技术对催化剂进行了表征. 结果表明, 铁或镍助剂的加入有助于提高 Ag/SiO2 催化剂的选择性. 其中, 铁的加入能增强活性组分银与载体间相互作用, 大大促进了银在载体表面上的分散, 使催化剂的初活性显著提高. 而钴或镍的加入虽然能略微减少反应过程中 Ag/SiO2 催化剂表面的积炭, 但加剧了银在反应过程中的烧结, 导致催化剂稳定性下降.     

Promotion effect of adsorbed water/OH on the catalytic performance of Ag/activated carbon catalysts for CO preferential oxidation in excess H2

Activated carbon (AC) supported silver catalysts were prepared by incipient wetness impregnation method and their catalytic performance for CO preferential oxidation (PROX) in excess H₂ was evaluated. Ag/AC catalysts, after reduction in H₂ at low temperatures (≤200 °C) following heat treatment in He at 200 °C (He200H200), exhibited the best catalytic properties. Temperature-programmed desorption (TPD), X-ray diffraction (XRD) and temperature-programmed reduction (TPR) results indicated that silver oxides were produced during heat treatment in He at 200 °C which were reduced to metal silver nanoparticles in H₂ at low temperatures (≤200 °C), simultaneously generating the adsorbed water/OH. CO conversion was enhanced 40% after water treatment following heat treatment in He at 600 °C. These results imply that the metal silver nanoparticles are the active species and the adsorbed water/OH has noticeable promotion effects on CO oxidation. However, the promotion effect is still limited compared to gold catalysts under the similar conditions, which may be the reason of low selectivity to CO oxidation in PROX over silver catalysts. The reported Ag/AC-S-He catalyst after He200H₂00 treatment displayed similar PROX of CO reaction properties to Ag/SiO₂. This means that Ag/AC catalyst is also an efficient low-temperature CO oxidation catalyst.     

Effect of silver modification on structure and catalytic performance of Ni-Mg/diatomite catalysts for edible oil hydrogenation

Silver modified Mg-Ni/diatomite materials with ratios of SiO₂/Ni = 1.07 and Mg/Ni = 0.1, differing in Ag content (Ag/Ni = 0.025 and 0.1) were prepared by the precipitation–deposition method. The effects of silver presence and content on the structure, morphology, texture and H₂-adsorption capacity of the obtained precursors were studied by X-ray diffraction, scanning electron microscopy, Hg-porosimetry and H₂-chemisorption techniques. The catalytic performance of the corresponding catalysts in the soybean oil hydrogenation was investigated. The increase of the silver loading resulted in the development of macroporosity and increase in the total sample porosity. The decrease of both H₂-adsorption capacity and hydrogenation activity are related to the metallic silver covering and blocking effects on the Ni²⁺ species, thus hampering the access of hydrogen. The decrease of hydrogenation activity and favorable limiting of cis–trans isomerization on the silver modified catalyst are explained by Horiuti–Polanyi mechanism based on the assumption that hydrogenation and isomerization proceed at the same active metallic nickel sites via half-hydrogenated intermediates.It was shown that the adjustment of the catalyst composition by changing the content of silver modifier offers the possibility to control the total amount of solid fat content, stearic acid and detrimental trans fatty acids in the hydrogenated derivatives. The catalyst with higher silver content is proposed as a promising candidate for selective edible oil hydrogenation catalyst.     

Fibroin-functionalized magnetic carbon nanotube as a green support for anchoring silver nanoparticles as a biocatalyst for A3 coupling reaction

Novel and powerful fibroin-functionalized magnetic carbon nanotube–supported silver nanoparticles (CNT–Fe₃O₄–fibroin–Ag) were successfully synthesized as a nontoxic and inexpensive biocatalyst. The structure of the organic–inorganic hybrid bionanocomposite was characterized by various techniques such as Fourier transform infrared spectroscopy, thermogravimetric analysis, energy-dispersive X-ray, field emission-scanning electron microscopy, transmission electron microscopy, X-ray diffraction, vibrating sample magnetometry, atomic absorption spectroscopy, and inductively coupled plasma-optical emission spectrometry. Then, the catalytic activity of synthesized bionanocomposite was evaluated in the three-component A³ coupling reaction under solvent-free conditions with good to excellent yields. Several propargylamine derivatives were synthesized by the reaction of different aldehydes with amines and phenylacetylene. Biodegradability, biocompatibility, availability, easy synthesis, high stability, high-throughput, cost-effectiveness, and efficient magnetic separation are some advantages of this catalyst that make it economically justified and sustainable. Moreover, the catalyst can be recycled for several runs without appreciable loss in its catalytic activity.     

Preparation and characterization of Cu supported on 2-(1H-benzo[d]imidazol-2-yl)aniline-functionalized Fe3O4 nanoparticles as a novel magnetic catalyst for Ullmann and Suzuki cross-coupling reactions

Copper supported on 2-(1H-benzo[d]imidazol-2-yl)aniline (BIA)-functionalized Fe₃O₄ nanoparticles (Cu-BIA-Si-Fe₃O₄) as a novel magnetic catalyst was designed and used for the synthesis of new products via Ullmann and Suzuki cross-coupling reactions. The Ullmann reaction was performed by mixing arylboronic acid with aniline derivatives in dimethylsulfoxide solvent. Also, diaryls were synthesized via Suzuki C–C reactions between aryl halides and phenylboronic acid in the same solvent. The prepared materials and catalyst were characterized with various analytical techniques. The Cu-BIA-Si-Fe₃O₄ catalyst demonstrated catalytic efficiency with good to excellent yields for both types of reactions in comparison with commercial palladium catalysts. Also, the catalyst could be recovered by a simple filtration and retained its activity even after several cycles.     

Green bio‐based synthesis of Fe2O3@SiO2‐IL/Ag hollow spheres and their catalytic utility for ultrasonic‐assisted synthesis of propargylamines and benzo[b]furans

A novel magnetic hybrid system containing nano‐magnetic Fe₂O₃ hollow spheres, silica shell, [pmim]Cl ionic liquid and silver nanoparticles was synthesized and characterized. The silver nanoparticles were prepared via biosynthesis using Achillea millefolium flower as reducing and stabilizing agent. The hybrid system was successfully used as an efficient and reusable catalyst for promoting green ultrasonic‐assisted A³ and KA² coupling reactions as well as benzo[b]furan synthesis. It was found that decoration of the magnetic core with non‐magnetic moieties decreased the maximum saturation magnetization. However, the catalyst was still superparamagnetic and could be simply separated from the reaction mixture using an external magnet. The heterogeneous nature of the catalyst was also confirmed by studying its reusability and stability and the leaching of silver. Use of aqueous media, high yields, short reaction times, broad substrate tolerance and low required amount of catalyst are the merits of this protocol.     

Synergetic effect of heterojunction and doping of silver on ZnNb2O6 for superior visible-light photocatalytic activity and recyclability

This work reports the synthesis of Ag/ZnNb₂O₆ heterojunctions by solid-state approach followed with the photoreduction of silver. It was found that Ag decorated ZnNb₂O₆ catalyst was provided with dual roles of silver, including homogeneous doping of Ag ions into ZnNb₂O₆ host lattice and a large amount of heterojunctions due to the monodispersion of tiny Ag nanoparticles deposited on ZnNb₂O₆ surface, thereby showing the abnormal visible-light absorption ascribed to the interband introduction and the strong surface plasmon resonance. The photocatalytic effects of silver doping and heterojunctions in visible-light irradiation were investigated, which showed Ag(6 wt.%)/ZnNb₂O₆ catalyst had the optimal photocatalytic efficiency (96.5–98.2% within 2 h) for the photodegradation of five various dyes and high recyclability during the photocatalytic degradation of methyl orange.