室温离子液体催化对羟基苯甲酸乙酯的合成研究

[目的]研究室温离子液体催化对羟基苯甲酸乙酯的合成。[方法]选择4种1,3二烷基咪唑离子液体催化合成对羟基苯甲酸乙酯反应,考察反应温度、反应时间、催化剂用量、酸醇摩尔比对反应产率的影响及离子重复使用性能。[结果]以[BMIm]BF4为催化剂,其用量为3 ml,酸醇摩尔比为1.0∶2.5,反应时间为2.5 h,反应温度为80℃,产率最高,为79.7%;且产物与离子液体催化体系不容而分层,便于分离,离子液体可以稳定重复使用5次。[结论]离子液体可以作为一种新型绿色溶剂,有效催化合成对羟基苯甲酸乙酯反应,并可减少环境污染。     

Asymmetric electrophilic fluorination using an anionic chiral phase-transfer catalyst

The discovery of distinct modes of asymmetric catalysis has the potential to rapidly advance chemists' ability to build enantioenriched molecules. As an example, the use of chiral cation salts as phase-transfer catalysts for anionic reagents has enabled a vast set of enantioselective transformations. Here, we present evidence that a largely overlooked analogous mechanism wherein a chiral anionic catalyst brings a cationic species into solution is itself a powerful method. The concept is applied to the enantioselective fluorocyclization of olefins with a cationic fluorinating agent and a chiral phosphate catalyst. The reactions proceed in high yield and stereoselectivity, especially considering the scarcity of alternative approaches. This technology can in principle be applied to the large portion of reaction space that uses positively charged reagents and reaction intermediates.     

Dynamic control of chiral space in a catalytic asymmetric reaction using a molecular motor

Enzymes and synthetic chiral catalysts have found widespread application to produce single enantiomers, but in situ switching of the chiral preference of a catalytic system is very difficult to achieve. Here, we report on a light-driven molecular motor with integrated catalytic functions in which the stepwise change in configuration during a 360° unidirectional rotary cycle governs the catalyst performance both with respect to activity and absolute stereocontrol in an asymmetric transformation. During one full rotary cycle, catalysts are formed that provide either racemic (R,S) or preferentially the R or the S enantiomer of the chiral product of a conjugate addition reaction. This catalytic system demonstrates how different molecular tasks can be performed in a sequential manner, with the sequence controlled by the directionality of a rotary cycle.     

丙酸香叶酯的催化合成(英文)

[目的]进行丙酸香叶酯的合成并优化合成条件。[方法]在敞开体系中合成中孔分子筛Al-MCM-41。通过X射线衍射(XRD)、红外光谱(FT-IR)、NH3程序升温脱附(NH3-TPD)、N2吸附-脱附和气相色谱(GC)等方法对所合成样品的结构和催化性能进行表征分析。用其催化合成丙酸香叶酯,考察了反应时间、反应温度、催化剂用量、反应物配比及催化剂再生对香叶醇酯化反应结果的影响。[结果]合成的样品具有中孔分子筛的六方介孔结构以及良好的长程有序性和结晶度,属于典型的中孔材料,分子筛表面有弱酸中心。最佳的反应条件是n(香叶醇)/n(丙酸)=1.0∶1.5,反应温度为120℃,反应时间为8h,但香叶醇的转化率仅为40.01%,丙酸香叶酯的选择性为70.01%。催化剂使用到第5次时有失活现象,可通过焙烧除去掩盖酸中心的积碳,使催化剂的活性和选择性得到恢复。[结论]得到了丙酸香叶酯的合成优化条件,为进一步研究奠定基础。     

Oscillating stereocontrol: a strategy for the synthesis of thermoplastic elastomeric polypropylene

A strategy has been developed for the synthesis of thermoplastic elastomeric polypropylene based on the catalytic activity of the unbridged metallocene bis(2-phenylindenyl)zirconium dichloride [(2-PhInd)(2)ZrCl(2)]. This catalyst was designed to isomerize between achiral and chiral coordination geometries during the polymerization reaction to produce atactic-isotactic stereoblock polymers. The metallocene precursor (2-PhInd)(2)ZrCl(2) in the presence of methylaluminoxane polymerizes propylene to yield rubbery polypropylene. The isotacticity of the polymer, described by the isotactic pentad content, increases with increasing propylene pressure and decreasing polymerization temperature to produce polypropylenes with an isotactic pentad content ranging from 6.3 to 28.1 percent.     

镁铝钴复合氧化物催化合成OHAA保鲜新材料研究

研究镁铝钴复合氧化物新型催化剂的合成,并以此催化剂催化合成农产品保鲜新材料环氧乙烷高级脂肪醇（OHAA）。薄层色谱表明镁铝钴复合氧化物催化合成的OHAA分布指数达到80%以上,具有很好的窄分布效果。通过催化剂用量、反应温度、反应压力三者间的L9(33)正交试验,得出镁铝钴复合氧化物催化OHAA合成的最佳反应条件为催化剂用量3%,温度160℃, 压力0.6 MPa。     

催化合成法对氯化石蜡质量的影响

本文讨论氯化石蜡催化合成方法的特点及其对氯蜡产品质量的影响.由于催化剂的使用,提高了反应速度,缩短了反应周期,降低了反应温度和增加了过程对原料纯度的适应性,因而提高了产品的热分解温度,减少氯蜡的分解和副反应,使产品质量明显提高.     

KF/K2CO3/γ-Al2O3催化合成反式阿魏酸的研究

[目的]对KF/K2CO3/γ-Al2O3催化合成反式阿魏酸进行研究。[方法]以香兰素和丙二酸为原料,KF/K2CO3/γ-Al2O3为催化剂,经Knoevenagel缩合反应催化合成反式阿魏酸,考察反应时间、香兰素与丙二酸物质的量之比和催化剂用量等条件对反式阿魏酸收率的影响。[结果]催化合成的最佳工艺条件为:香兰素7.6 g(0.05 mol),n(香兰素)∶n(丙二酸)=1∶1.20,KF/K2CO3/γ-Al2O31.00 g,乙酸正丁酯25 ml,反应时间2 h;在此条件下,产品收率达到65%以上,且催化剂可以重复使用6次,收率依然超过60%。[结论]KF/K2CO3/γ-Al2O3具有良好的催化活性。     

Mn2+催化臭氧化去除腐殖酸的试验研究

以天然水体中常见的金属离子Mn2+为催化剂,研究了其对水中溶解性腐殖酸的催化臭氧化效能.结果表明,Mn2+对臭氧化去除腐殖酸有明显的催化作用,反应25 min,对腐殖酸的去除率可达82.3%,较单独臭氧化提高了24.3%;通过Na2CO3对催化反应的影响验证了Mn2+催化臭氧化反应遵循自由基反应原理;同时也发现催化效率随着臭氧流量的增大而提高,随着pH值的升高而提高;且少量Mn2+投加即可产生明显的催化作用,过量则会产生抑制作用.     

A powerful chiral counterion strategy for asymmetric transition metal catalysis

Traditionally, transition metal-catalyzed enantioselective transformations rely on chiral ligands tightly bound to the metal to induce asymmetric product distributions. Here we report high enantioselectivities conferred by a chiral counterion in a metal-catalyzed reaction. Two different transformations catalyzed by cationic gold(I) complexes generated products in 90 to 99% enantiomeric excess with the use of chiral binaphthol-derived phosphate anions. Furthermore, we show that the chiral counterion can be combined additively with chiral ligands to enable an asymmetric transformation that cannot be achieved by either method alone. This concept of relaying chiral information via an ion pair should be applicable to a vast number of metal-mediated processes.     

微波辅助雷尼镍-铝合金催化剂催化1,4-二氯苯快速脱氯反应动力学研究

利用雷尼镍-铝合金催化剂的高催化活性,提出了使用微波辅助雷尼镍-铝合金催化1,4-二氯苯还原脱氯的方法。结果表明,在微波辅助雷尼镍-铝合金催化剂条件下,1,4-二氯苯还原脱氯的反应符合二级反应动力学方程。1,4-二氯苯脱氯的反应速率常数k1在35和50℃下分别为0.037 6和0.151 mol/(L.min),反应活化能为76.66 kJ/mol。研究还表明,在微波辅助雷尼镍-铝合金催化剂的条件下,35℃时,1,4-二氯苯10 min脱氯率达到90%,并且反应同时脱掉两个氯,能达到高效脱氯的目的。由此可知,微波辅助雷尼镍-铝合金催化脱氯的方法应用于多氯苯类物质脱氯取得良好的效果。     

Mechanism and stereoselectivity of asymmetric hydrogenation

Rhodium complexes containing chiral phosphine ligands catalyze the hydrogenation of olefinic substrates such as alpha-aminoacrylic acid derivatives, producing chiral products with very high optical yields. Elucidation of the mechanisms of such reactions leads to the conclusion that the stereoselection is dictated not by the preferred initial binding of the substrate to the chiral catalyst, but rather by the much higher reactivity of the minor diastereomer of the catalyst-substrate adduct corresponding to the less favored binding mode.     

固体超强酸催化合成中碳链甘油酯试验研究

进行自制固体超强酸催化剂催化合成中碳链甘油酯试验,讨论其适宜的合成条件。试验结果表明:用固体超强酸SO42-/AxBy催化合成中碳链甘油酯效果显著,当反应时间为5 h、温度180℃、催化剂剂量为0.7%时催化效果最佳,得到的中碳链甘油酯的酸值为0.56 mg KOH/g,产品为无色。     

Renewable hydrogen from nonvolatile fuels by reactive flash volatilization

Droplets of nonvolatile fuels such as soy oil and glucose-water solutions can be flash evaporated by catalytic partial oxidation to produce hydrogen in high yields with a total time in the reactor of less than 50 milliseconds. Pyrolysis, coupled with catalytic oxidation of the fuels and their fragments upon impact with a hot rhodium-cerium catalyst surface, avoids the formation of deactivating carbon layers on the catalyst. The catalytic reactions of these products generate approximately 1 megawatt of heat per square meter, which maintains the catalyst surface above 800 degrees C at high drop impact rates. At these temperatures, heavy fuels can be catalytically transformed directly into hydrogen, carbon monoxide, and other small molecules in very short contact times without the formation of carbon.     

正丁醇开环环氧菜籽油制备脂肪酸多元醇的研究

以菜籽油为原料,首先合成环氧菜籽油,再由合成的环氧菜籽油与正丁醇在对甲苯磺酸作催化剂的条件下,通过开环加成反应制备高羟值菜籽油多元醇。研究了水用量、正丁醇用量、反应时间、反应温度等因素对合成反应的影响,并对产物的羟值和黏度进行测试。结果表明,当水用量为50g,正丁醇用量为1mol,反应温度为70℃,反应时间为60min时,菜籽油多元醇的羟值相对较高。最后,对高羟值产物进行了红外（IR）分析。     

以度米芬为相转移催化剂合成苯甲酸

[目的]采用高锰酸钾氧化法,研究季铵盐类化合物度米芬作为一种相转移催化剂合成苯甲酸的催化性能。[方法]分析比较反应温度、催化剂用量、高锰酸钾与甲苯的用量,对相转移催化剂度米芬和苄基三乙基氯化铵（TEBA）制备苯甲酸的催化性能的影响。[结果]确定以度米芬作为相转移催化剂合成苯甲酸的最佳工艺条件为：高锰酸钾与甲苯的摩尔用量比为2.5：1.0,反应温度为90℃,反应时间可缩短至5h,收率达67.20%。[结论]通过对度米芬在苯甲酸合成中催化性能的研究,表明度米芬是一种新型的环境友好型相转移催化剂。     

用萘和氯乙酸合成萘乙酸的研究

采用单因素试验和正交试验相结合,对以三氯化铁为主催化剂,溴化钾为助催化剂,萘与氯乙酸为原料合成萘乙酸的反应过程进行了系统研究.结果表明,保持反应温度在200℃左右,反应时间为15 h,萘/氯乙酸的摩尔比为2.5,反应物/催化剂质量比为32.5,主催化剂/助催化剂摩尔比为1/5时,产品收率达53.9%.本研究较传统的合成萘乙酸法缩短了反应时间,提高了反应产率.     

Homogeneous catalysis--new approaches to catalyst separation,recovery, and recycling

Homogeneous catalysts have many attractive properties, such as high selectivities. However, many homogeneous catalytic systems cannot be commercialized because of difficulties associated with separating the products from the catalyst. Recent approaches to tackling this problem are reviewed and compared.     

Helical polyacetylene synthesized with a chiral nematic reaction field

Helical polyacetylene was synthesized under an asymmetric reaction field consisting of chiral nematic (N*) liquid crystals (LCs). The chiral nematic LC was prepared by adding a chiroptical binaphthol derivative as a chiral dopant to a mixture of two nematic LCs. Acetylene polymerizations were carried out using the catalyst titanium tetra-n-butoxide-triethylaluminum dissolved in the chiral nematic LC solvent. The polyacetylene film was shown by scanning electron microscopy to consist of clockwise or counterclockwise helical structure of fibrils. A Cotton effect was observed in the region of the pi --> pi* transition of the polyacetylene chain in circular dichroism spectra. The high electrical conductivities of approximately 1500 to 1800 siemens per centimeter after iodine doping and the chiral helicity of these films may be exploited in electromagnetic and optical applications.     

2 + 2] photocycloadditions in the synthesis of chiral molecules

A strategy for the synthesis of chiral molecules that receives growing popularity among organic chemists employs the photochemically mediated [2 + 2] cycloaddition reaction. These reactions can be performed on a multigram scale and often proceed with high yield and with stereocontrol. These features, in combination with the useful properties of the four-membered ring photoproducts in subsequent chemical transformations, make them attractive options in the early stage of a synthesis design. Various combinations of unsaturated functional groups can participate in this reaction process. Accordingly, these chemical reactions can be economical solutions to problems relating to the synthesis of a variety of target molecules.