Yb(OTf)3催化苯乙酮、芳香醛和芳香胺的Mannich反应:三组分 "一锅法"合成β-氨基酮衍生物

报道了稀土化合物Yb(OTf)3催化的苯乙酮、芳香醛和芳香胺Mannich反应,三组分"一锅法"合成了一系列的β-氨基酮衍生物.该方法操作简单、条件温和、产率较高、催化剂可重复使用,且对环境友好.     

脱氢枞基α-氨基膦酸酯的合成

以Yb(OTf)3为催化剂,聚氧乙基-α-生育酚癸二酸酯(PTS)为助溶剂,水为溶剂,经三组分[脱氢枞胺(1)、亚磷酸二乙酯(2)和芳醛(3a~3f)]缩合反应合成了6个含脱氢枞基的α-氨基膦酸酯衍生物(4a~4f),产率65%~75%,其结构经1H NMR,FT-IR和EI-MS确证。考察了溶剂和助溶剂对4a产率的影响。结果表明:在最优反应条件[以水为溶剂,1 1 mmol,2 1.2 mmol,3a 1 mmol,Yb(OTf)30.01 mmol,PTS 2 m L,于室温反应1 h]下,4a产率71%。Yb(OTf)3循环使用5次,4a产率64%。     

三氟甲烷磺酸稀土盐对聚丙烯热稳定性的影响及机理

通过熔融共混将三氟甲烷磺酸镱[Yb(OTf)₃]和三氟甲烷磺酸镧[La(OTf)₃]添加至聚丙烯(PP)中, 制得PP/Yb和PP/La材料, 并对其热稳定性进行表征. 热失重分析(TGA)和差示扫描量热分析(DSC)结果显示, Yb(OTf)₃和La(OTf)₃均可以显著提高聚丙烯的热稳定性. 当Yb(OTf)₃添加量仅为1%(质量分数)时, PP的起始分解温度从275 ℃提高至305 ℃, 最大分解温度从384 ℃提高至405 ℃, 160 ℃下的氧化诱导时间从12.1 min延长至43.0 min, 热焓从1907 J/g降低至483 J/g; 而PP/La1的起始分解温度、 最大分解温度、 160 ℃下的氧化诱导时间和热焓分别为300 ℃, 409 ℃, 18.6 min和633 J/g. 结果表明, La(OTf)₃对聚丙烯热稳定性的改善作用弱于Yb(OTf)₃, 对2种稀土盐产生不同实验结果的原因进行分析并提出机制. 由于阴离子和阳离子的共同作用, Yb(OTf)₃和La(OTf)₃均可提高PP的热氧稳定性. La(OTf)₃中三氟甲烷磺酸根的自由基捕捉能力和稀土离子的配位能力发挥主要作用, 而Yb(OTf)₃中的稀土离子的高反应活性也起到关键作用.     

光学活性(甲基)丙烯酰胺的立体定向自由基聚合——立体控制机理探讨

利用Lewis酸三氟甲磺酸镱(Yb(OTf)3)调控(S)-N-(2-羟基-1-苯乙基)甲基丙烯酰胺((S)-HPEMA)和(S)-N-(2-羟基-1-苯乙基)丙烯酰胺((S)-HPEA)的自由基聚合,得到相应的光学活性聚合物;研究了反应条件对聚合物立体结构的影响,发现以甲醇和正丁醇为溶剂时,Yb(OTf)3的存在可显著提高聚合物的mm三元组的含量,而以DMSO为溶剂时,Yb(OTf)3对聚合物的立构规整性没有明显改变;通过1H-NMR研究了Yb(OTf)3与单体之间的相互作用,结果表明单体的酰胺基团与Lewis酸的稀土金属离子间的配位以及单体的羟基与Lewis酸的三氟甲磺酸根间的氢键影响了单体的加成方向和聚合物的立体结构.     

新型手性稀土配合物的合成、表征及其在不对称催化反应中的应用

作为符合绿色化学标准的稀土三氟甲磺酸盐Ln(OTf)3化合物打破了传统路易斯酸催化的模式，以其在水中稳定、催化用量少(一般少于10 mol％)和可回收再用的独特性质而受到广泛关注。Ln(OTf)3化合物可以催化许多有机合成反应，得到多种多样重要的合成中间体。但是，到目前为止，手性     

无溶剂条件下Yb(OTf)3催化的亚甲基化合物和醛的Knoevenagel反应

在Yb(OTf)₃催化下, 不用任何溶剂, 将活泼亚甲基化合物和各类醛进行Knoevenagel反应, 得到相应的取代烯烃衍生物. 此法操作简便, 对环境友好, 具有很高的反应产率, 且副产物少; 此外, 催化剂能够在进行反复回收利用之后仍然保持很高的催化活性.     

Yb(OTf)3催化苯乙酮、芳香醛和芳香胺的Mannich反应: 三组分“一锅法”合成β-氨基酮衍生物

报道了稀土化合物Yb(OTf)₃催化的苯乙酮、芳香醛和芳香胺Mannich反应, 三组分“一锅法”合成了一系列的β-氨基酮衍生物. 该方法操作简单、条件温和、产率较高、催化剂可重复使用, 且对环境友好.     

离子液体中Yb(OTf)_3催化下喹唑啉酮衍生物的绿色合成

以邻氨基苯甲酰胺和芳醛为原料,离子液体[BMIm]Br为溶剂,Yb(OTf)3为催化剂室温下合成了一系列的2-芳基-2,3-二氢化喹唑啉-4-(1H)-酮衍生物.和其他方法相比,该方法具有反应条件温和、产率高(85%～96%)、环境友好等优点.产物的结构通过熔点,IR,1H NMR和高分辨质谱分析确证.     

有机锡氧簇合物选择性催化醛的硅氢化反应研究

有机锡氧簇合物在有机合成反应中体现出良好的催化活性. 以Bu₂SnO与TfOH (OTf＝CF₃SO₃)直接反应合成了有机锡氧簇合物[Bu₂Sn(OH)OTf]₂, 考察了[Bu₂Sn(OH)OTf]₂催化醛的硅氢化反应. 结果表明不仅催化活性高, 而且具有很高的选择性. 它仅对反应物的醛基起作用, 对分子内和反应体系中其它活泼基团如酮、酯、烯、炔等不起作用.     

环境友好型Michael加成的研究进展

Michael加成反应是有机合成领域一类非常重要的反应.随着人们环保意识的增强和对绿色化学研究的深入,环境友好型Michael加成取得了诸多成功.综述了近5年来离子液体、酶催化、负载固相催化、聚乙二醇(PEG)等参与的Michael加成反应的研究进展.着重分析了反应体系的高效性、催化剂可能的催化反应机理以及催化剂的循环使用性,并以此对环境友好型Michael加成的发展做出了展望.     

Synthesis of 1,8-Dioxo-octahydroxanthene Derivatives Catalyzed by p-Dodecylbenezenesulfonic Acid in Water

With the increasing concerns of the environment, more and more chemists are devoted to the research of the "green synthesis" which means that the reagent, solvent and catalyst are environmentally friendly in the organic chemical reactions. The importance of aqueous reaction is now generally recognized, and development of carbon-carbon bond-forming reactions that can be carried out in aqueous media is now one of the most challenging topics in organic synthesis.[1]Herein, we report a clean synthesis of 3,3,6,6-tetramethyl-9-aryl-1,8-dioxo-octahydroxanthene derivatives from aromatic aldehyde and 5,5-dimethyl-1,3-cyclohexadione using p-dodecylbenezenesulfonic acid (DBSA) as the catalyst in water.This method provides several advantages such as high yield, simple work-up procedure and environmental friendliness and water was chosen as a green solvent. All the products were characterized by m.p., 1H NMR, IR and elemental analyses.     

DFT calculations induced a regiochemical outcome revision of the Diels-Alder reaction between levoglucosenone and isoprene

An appealing inversion in the regiochemical outcome of Diels-Alder reactions between levoglucosenone (1) and its α-bromo derivative (5) with isoprene (2) was studied computationally. Based on different DFT calculations we concluded that both reactions should display the same regioselectivity. This result was further validated experimentally.     

Water-soluble ionic liquids as novel stabilizers in suspension polymerization reactions: engineering polymer beads

Aqueous solutions of ionic liquids have been used as novel and environmentally friendly reaction media to synthesize and "control" the size of different cross-linked polymer beads by suspension polymerization reactions. It was found that the investigated ionic liquids can act as novel stabilizing agents of the suspensions as a result of their surface-active properties. The results have demonstrated that the average size of polymer beads can be varied from the macro- to the nanoscale and their surface area can also be "adjusted" by this synthetic approach. Furthermore, the use of a combination of ionic liquids and water for the synthesis of polymers, the simple isolation of the products formed in this polymerization procedure, as well as the recycling of the continuous medium for further reactions open up possibilities for the development of "new and green" polymerization processes.     

"Asymmetric" catalysis by lanthanide complexes

Catalysis with lanthanide (Ln) complexes has been underestimated for long time, although Ln(III) complexes have great advantages as Lewis acid catalysts for "asymmetric" carbon-carbon bond-forming reactions. Lanthanide complexes are highly active in ligand-substitution reactions, especially with hard ligands. The association with substrates and dissociation of products are achieved fast enough for high catalyst efficiency. The asymmetric catalysis of organic reactions can be greatly advanced by the use of Ln complexes with chiral ligands such as binaphthol (binol). Ln(II) complexes are good reducing agents, which can be used in a wide variety of synthetically important reactions; when chiral ligands are used, many of these reactions are highly stereoselective. In the context of "green chemistry", the development of asymmetric Ln catalysts, and their recyclable use, is of increasing importance. This review gives an overview of the most recent developments in catalysis with lanthanide(II) and lanthanide(III) complexes.     

Base-free Mizoroki-Heck reaction catalyzed by rhodium complexes

A base-free rhodium-catalyzed Mizoroki-Heck (M-H) reaction using potassium aryltrifluoroborates as the arylating agent of alkenes and acetone as a green "oxidant" is described. Thanks to the ready availability of organoboranes, this reaction should constitute an interesting alternative to conventional M-H reactions using aryl halides.     

Computational mechanistic studies of acceptorless dehydrogenation reactions catalyzed by transition metal complexes

Acceptorless dehydrogenation (AD) that uses non-toxic reagents and produces no waste is a type of catalytic reactions toward green chemistry. Acceptorless alcohol dehydrogenation (AAD) can serve as a key step in constructing new bonds such as C-C and C-N bonds in which alcohols need to be activated into more reactive ketones or aldehydes. AD reactions also can be utilized for hydrogen production from biomass or its fermentation products (mainly alcohols). Reversible hydrogenation/ dehy-drogenation with hydrogen uptake/release is crucial to realization of the potential organic hydride hydrogen storage. In this article, we review the recent computational mechanistic studies of the AD reactions catalyzed by various transition metal complexes as well as the experimental developments. These reactions include acceptorless alcohol dehydrogenations, reversible dehydrogenation/hydrogenation of nitrogen heterocycles, dehydrogenative coupling reactions of alcohols and amines to construct C-N bonds, and dehydrogenative coupling reactions of alcohols and unsaturated substrates to form C-C bonds. For the catalysts possessing metal-ligand bifunctional active sites (such as 28, 45, 86, 87, and 106 in the paper), the dehydrogenations prefer the "bifunctional double hydrogen transfer" mechanism rather than the generally accepted-H elimination mechanism. However, methanol dehydrogenation involved in the C-C coupling reaction of methanol and allene, catalyzed by the iridium complex 121, takes place via the-H elimination mechanism, because the Lewis basicity of either the-allyl moiety or the carboxyl group of the ligand is too weak to exert high Lewis basic reactivity. Unveiling the catalytic mechanisms of AD reactions could help to develop new catalysts.     

Reactions between or within molecular crystals

Reactions that occur within or between molecular crystals, in particular those reactions that are activated by mechanical methods, are reviewed. The focus is on processes (whether intrasolid or intersolid) that are controlled primarily by supramolecular bonding, such as template cycloadditions, formation of inclusion compounds, reactions between molecular crystals by the reassembling of noncovalent bonds, and the formation of complexes and coordination compounds. It is proposed that solvent-free mechanochemical methods, for example, cogrinding, milling, and kneading, represent viable "green" routes for the preparation of novel molecular and supramolecular solids.     

Desferrioxamine dehydrogenates bilirubin in two stages,leading to a 1:1 red‐coloured adduct. Characterization of the products by high‐performance liquid chromatography/electrospray ionization mass spectrometry

We have used open‐chain tetrapyrroles, such as bilirubin, as molecular probes to investigate the pro‐oxidant activity of desferrioxamine (DES) and its modulation by Trolox. On exposure to Fe‐EDTA/H₂O₂, bilirubin and mesobilirubin underwent bleaching. When DES was present, bleaching was prevented and both rubins were converted into green‐coloured derivatives and then into red pigments. Trolox added with DES inhibited the colour changes induced by DES. The oxidative products were resolved from their parent compounds by high‐performance liquid chromatography (HPLC) and studied by electrospray ionization mass spectrometry and by UV/visible spectroscopy. The green products were identified as biliverdin or mesobiliverdin; the red pigments as the 1:1 molar adduct of DES with biliverdin or mesobiliverdin, less two hydrogens in both cases. It is concluded that DES exercises its oxidative activity through nitroxyl oxidizing radicals capable of efficient hydrogen abstraction, dehydrogenating either rubin to the corresponding verdin. A diradical derivative of DES (bearing two nitroxyl radicals in the same molecule) may be involved in the oxidation of verdins to red pigments, through concerted dehydrogenation and adduct formation. These results shed further light on the redox properties of bilirubin, DES and Trolox, and their interactions. They provide further evidence of the pro‐oxidant activity of DES and suggest a more general biological significance, as rapid removal of bilirubin by bleaching or dehydrogenation may have pharmacological/toxicological implications in severe jaundice. Copyright © 2008 John Wiley & Sons, Ltd.     

Reactions in micellar systems

The notion of "green chemistry" has encouraged even synthetic organic chemists to include water as a solvent. Incredible selectivities and activities can be achieved through the addition of amphiphiles with a defined structure. The morphology of supramolecular assemblies or associates formed by surfactants vary according to the temperature and concentration. As a rule, reactions are typically conducted using simple spherical aggregates, that is, micelles in the nanometer range. The strong polarity gradient present between the hydrophilic surface and the hydrophobic core of the micelle means that both nonpolar and polar reagents can be solubilized. This solubilization results in reactants becoming more concentrated within the micelle than in the surrounding water phase and leads to an acceleration of the reaction and causes selective effects. The kinetic treatment of reactions in micellar systems can be accomplished by considering them as microheterogeneous two-phase systems.     

Synthesis and Solvatochromatic properties of 9-(4-Aminophenylethynyl)-10-(4-nitrophenylethynyl)anthracene

9-(4-Aminophenylethynyl)-10-(4-nitrophenylethynyl)anthracene (2) was synthesized in high yield by using a route involving sequential Sonogashira cross coupling reactions of 9-bromo-10-iodoanthracene with 4-nitrophenylacetylene and 4-aminophenylacetylene. Solvatochromism was observed in the absorption and fluorescence spectra of 2 in a variety of solvents. In less polar solvents, such as hexane and benzene, the fluorescence emission band of 2 appears in the green to orange region while this substance does not fluoresce in polar solvents, such as acetonitrile and DMF.