Proline-catalysed Mannich reactions of acetaldehyde

Small organic molecules recently emerged as a third class of broadly useful asymmetric catalysts that direct reactions to yield predominantly one chiral product, complementing enzymes and metal complexes. For instance, the amino acid proline and its derivatives are useful for the catalytic activation of carbonyl compounds via nucleophilic enamine intermediates. Several important carbon-carbon bond-forming reactions, including the Mannich reaction, have been developed using this approach, all of which are useful for making chiral, biologically relevant compounds. Remarkably, despite attempts, the simplest of all nucleophiles, acetaldehyde, could not be used in this way. Here we show that acetaldehyde is a powerful nucleophile in asymmetric, proline-catalysed Mannich reactions with N-tert-butoxycarbonyl (N-Boc)-imines, yielding beta-amino aldehydes with extremely high enantioselectivities-desirable products as drug intermediates and in the synthesis of other biologically active molecules. Although acetaldehyde has been used as a nucleophile in reactions with biological catalysts such as aldolases and thiamine-dependent enzymes, and has also been employed indirectly, its use as an inexpensive and versatile two-carbon nucleophile in asymmetric, small-molecule catalysis will find many practical applications.     

室温离子液体及其在绿色化学中的应用

~~烷基取代咪唑阳离子 (图 1 )研究最多 ,表 1总结了近年来开发研究的此类阳离子的种类及结构 .可以组成室温离子液体的阴离子 ,目前的研究除 Al Cl4-,NO2 -和干燥时易爆的 NO3 -,Cl O4-外 ,含氟阴离子为多 ,主要有 :BF4-,PF6-,As F6-,Sb F6-,F ( HF ) n-,CF3 SO3 -,CF3 CF2 CF2 CF2 SO3 -,( CF3 SO2 ) 2 N-,( CF3 SO2 ) 3 C-,CF3 COO-,CF3 CF2 CF2 COO-等 .图 1　烷基取代咪唑阳离子　　由各种阳离子和各种阴离子组合 ,可以得到一系列特性各异的室温离子液体 ,目前已报道的多为由表 1所示的烷基咪唑阳离子和含氟阴…     

Diels-Alder反应的全新认识

综述了１９篇参考文献中关于Ｄｉｅｌｓ－Ａｌｄｅｒ反应的研究新成果：水相Ｄｉｅｌｓ－Ａｌｄｅｒ反应;Ｃ６０的Ｄｉｅｌｓ－Ａｌｄｅｒ反应;超分子作用下的Ｄｉｅｌｓ－Ａｌｄｅｒ反应以及反双烯合成的应用。对Ｄｉｅｌｓ－Ａｌｄｅｒ反应的全新认识无论是对有机合成设计还是有机化学教学内容更新都具有重要意义。     

N-氧化物的应用和直接合成方法

N-氧化物是一类具有广泛生物活性的化合物,常用于各种药物合成的中间体或者本身就是药物;同时它们也可以作为有机化工中间体和催化剂等,在有机合成上起到非常重要的作用。传统的制备N-氧化物的方法是采用合适的氧化剂对含氮化合物进行N-氧化。此外,用直接合成方法,即在生成含氮化合物的同时发生N-氧化,也可以得到相应的N-氧化物。由于直接合成方法的一些优势和传统方法的诸多缺陷,本文着重总结了包括嘧啶类N-氧化物和喹喔啉类N-氧化物等在内的十类N-氧化物的直接合成方法,并简述了它们的应用。     

天然矿物低温催化脂肪酸酯水解反应动力学研究

选择十八烷酸甲酯为模型化合物,以10种天然矿物为载体,通过动力学方法考察了天然矿物对脂肪酸酯水解反应的催化作用。结果表明,地质低温条件下天然矿物对脂肪酸酯水解反应具有催化作用。粘土、碳酸盐和金属元素对于脂肪酸酯水解反应具有不同的催化作用。碳酸盐矿物相对于粘土矿物具有较低的催化水解反应活化能,过渡金属化合物矿物的催化反应活化能介于碳酸盐和粘土之间。     

负载型Au/Al2O3系列催化剂的研究进展

负载型金催化剂作为一种新型催化剂,它优异的催化氧化性能引起越来越多化学工作者的关注.Au/Al₂O₃是催化剂制备中大量使用的典型氧化物载体.综述了近年来以Au/Al₂O₃为载体的系列Au/Al₂O₃催化剂的制备方法、催化性能及其活性中心结构的研究状况和发展趋势,讨论的主要反应包括CO低温催化氧化为CO₂、汽车尾气净化、含卤有机化合物的消除和甲烷催化燃烧.     

H4C2N+氮杂阳离子的结构与反应性

组成为H4C2N^ 氮杂阳离子有烯丙基型和烯酮亚胺型两类，它们都有较强的亲电性和反应活性，通过环加成反应能导入一种含氮的杂环结构，生成新的氮杂环化合物，由于反应能在常温下进行，反应的原料容易得到，使得氮杂阳离子的反应在有机合成中有着重要的实用价值．应用量子化学理论及其计算方法，从理论上研究这类体系的骨架原子在不同位置时的结构及其异构体的稳定性，以及它们与含双键的分子进行环加成反应的机理，寻找其反应规律，对于在有机合成中正确认识和应用这类反应有着重要的指导意义。     

稀土催化剂(Ce、La)用于丙烷催化燃烧的研究进展

目的 挥发性有机物(VOCs)对人体健康和生态环境都有不良影响,已引发研究者的广泛关注。催化燃烧是处理VOCs的有效技术之一,具有去除效率高、无二次污染等优势。稀土元素Ce、La及其氧化物因特殊的理化性质常作为催化助剂或载体,在催化燃烧中起着重要作用。因此针对稀土催化剂(主要为Ce、La),综述了其在丙烷催化燃烧中的应用及相应的催化反应机制以及未来的发展方向。方法 通过对Ce基和La基催化剂在丙烷催化燃烧中的研究和应用进行综述,分析了稀土催化剂的反应机理及发展方向。结果 首先,Ce、La及其氧化物可调节催化剂的整体结构、形貌和比表面积等物理性质;同时,上述物质也可与催化剂内的其他金属相互作用,从而有效调控材料中的氧空位密度,最终增强对丙烷催化燃烧的反应活性。其次,CeO₂作为载体能与活性金属产生有赖于CeO₂形貌和晶面的金属-CeO₂相互作用,这会对催化剂的结构和性能产生极大影响。此外,也讨论了通过优化合成方法和表面改性所获得的La系钙钛矿催化剂在丙烷催化燃烧中的应用研究。结论 目前,稀土基催化剂的催化作用机制探索尚处于...     

含硫杂环化合物的合成与性质

含硫杂环化合物广泛存在于天然产物、香料和药物分子之中,具有特殊的气味以及重要的生物活性,有着广泛的用途。这类化合物也是有机合成中一类非常重要的中间体。因此,含硫杂环化合物的合成研究备受关注。本文阐述了近几年来含硫杂环化合物的合成研究进展,对其相关性能进行了评价,并对该领域的发展前景进行了展望。     

N杂环卡宾在催化有机合成中的应用

1991年,Arduengo等分离出第一个稳定的N杂环卡宾——咪唑-2-碳烯,之后,N杂环卡宾化学得到了迅速的发展,在多种催化反应中得到了广泛的应用.本文综述了N杂环卡宾在催化有机反应中的研究进展,如催化安息香缩合反应、Stetter反应、a3-d3极性反转反应、开环反应、酯基交换反应、开环聚合反应.     

相转移催化反应

无机盐与有机物由于互不相溶很难反应,使用相转移催化剂可以使水相中的无机盐和有机相中的有机物经历相转移催化过程发生化学反应,这在有机合成中具有重要意义.     

相转移催化反应

无机盐与有机物由于互不相溶很难反应,使用相转移催化剂可以使水相中的无机盐和有机相中的有机物经历相转移催化过程发生化学反应,这在有机合成中具有重要意义。     

A.Flavus Mediated Biotransformations for the Syntheses of Active A-oxyfunctionalized Compounds

1 Results Biotransformations are enzyme- and whole cell-catalysed conversions of non-natural substrates to products.They are important tools in organic synthesis,especially for the syntheses of chiral molecules,where the reactions catalysed may be asymmetric syntheses or the resolution of racemates.The main advantages associated with the use of single enantiomer compounds are increased specificity and the avoidance of adverse side effects[1].Whole cell reactions are advantegous over enzyme-catalyzed rea...     

有机反应中的超声波作用

本文概述超声波的发生、实施有机化学反应的方法及促进有机反应的基本原理。综述近两年来超声波技术在有机合成,特别是金属一液异相反应中的应用。     

环境友好催化剂──沸石分子筛与有机反应

系统地论述了环境友好催化剂（EnvtironmentallyFriendlyCatalysts）的类型，一些常用沸石分子筛的结构、分子筛催化剂的制备方法以及它们在有机反应和有机合成中的应用。     

Control of four stereocentres in a triple cascade organocatalytic reaction

Efficient and elegant syntheses of complex organic molecules with multiple stereogenic centres continue to be important in both academic and industrial laboratories. In particular, catalytic asymmetric multi-component 'domino' reactions, used during total syntheses of natural products and synthetic building blocks, are highly desirable. These reactions avoid time-consuming and costly processes, including the purification of intermediates and steps involving the protection and deprotection of functional groups, and they are environmentally friendly and often proceed with excellent stereoselectivities. Therefore, the design of new catalytic and stereoselective cascade reactions is a continuing challenge at the forefront of synthetic chemistry. In addition, catalytic cascade reactions can be described as biomimetic, as they are reminiscent of tandem reactions that may occur during biosyntheses of complex natural products. Here we report the development of an asymmetric organocatalytic triple cascade reaction for the synthesis of tetra-substituted cyclohexene carbaldehydes. This three-component domino reaction proceeds by way of a catalysed Michael/Michael/aldol condensation sequence affording the products with good to moderate yields (25-58 per cent). During this sequence, four stereogenic centres are formed with high diastereoselectivity and complete enantioselectivity. In addition, variation of the starting materials can be used to obtain diverse polyfunctional cyclohexene derivatives, which can be used as building blocks in organic synthesis.     

不对称催化氢化反应研究

不对称催化氢化反应具有完美的原子经济性和清洁高效等特点,是最受青睐的不对称合成方法之一。虽然人们已经发展了很多用于不对称催化氢化的催化剂,但是这些催化剂往往存在稳定性差、活性低、底物适用范围窄、反应条件苛刻等问题,真正高效的手性催化剂很少。通过系统深入的研究,发展了30多个用于不对称氢化反应的原创性手性螺环催化剂,实现了潜手性酮、α-取代羰基化合物、不饱和羧酸、非保护烯胺等4大类20多种不对称氢化反应,反应的活性和对映选择性处于目前的最好水平,其中部分反应已经被用于手性药物及其中间体的生产,在国内外产生了重要影响。     

Enantiospecific electrodeposition of a chiral catalyst

Many biomolecules are chiral--they can exist in one of two enantiomeric forms that only differ in that their structures are mirror images of each other. Because only one enantiomer tends to be physiologically active while the other is inactive or even toxic, drug compounds are increasingly produced in an enantiomerically pure form using solution-phase homogeneous catalysts and enzymes. Chiral surfaces offer the possibility of developing heterogeneous enantioselective catalysts that can more readily be separated from the products and reused. In addition, such surfaces might serve as electrochemical sensors for chiral molecules. To date, chiral surfaces have been obtained by adsorbing chiral molecules or slicing single crystals so that they exhibit high-index faces, and some of these surfaces act as enantioselective heterogeneous catalysts. Here we show that chiral surfaces can also be produced through electrodeposition, a relatively simple solution-based process that resembles biomineralization in that organic molecules adsorbed on surfaces have profound effects on the morphology of the inorganic deposits. When electrodepositing a copper oxide film on an achiral gold surface in the presence of tartrate ion in the deposition solution, the chirality of the ion determines the chirality of the deposited film, which in turn determines the film's enantiospecificity during subsequent electrochemical oxidation reactions.     

非均相稀土有机金属催化剂研究进展

近年来,非均相稀土有机金属催化剂由于其可克服均相稀土有机金属络合物固有的稳定性差以及难以重复使用等缺点,引起了人们的浓厚兴趣和足够重视．着重介绍了非均相稀土三氟磺酸基有机金属催化剂和非均相稀土胺基有机金属催化剂的研究进展及其在精细有机合成中的应用,并对将来稀土有机金属催化剂的设计合成进行了展望．     

Mechanical milling assisted by electrical discharge

Mechanical milling is an effective technique for the preparation of fine metallic and ceramic powders and can also be used to drive a wide range of chemical reactions. Milling devices include planetary machines, attritors and vibrational mills; products include amorphous, nanocrystalline and quasicrystalline materials, supersaturated solid solutions, reduced minerals, high-surface-area catalysts and reactive chemicals. During milling, solid-solid, solid-liquid and solid-gas reactions are initiated through repeated deformation and fracture of powder particles. A separate materials synthesis and processing technique involves reacting a material in a gas atmosphere under an electrical discharge. Here we show that the application of low-current, high-voltage electrical impulses during milling can result in both faster reactions and new synthesis and processing routes. We demonstrate the effects of glow (cold) and spark (hot) discharge milling on particle fracture for brittle, low-conductivity materials and ductile metals. Glow discharge milling was found to promote solid-gas reactions whereas spark discharge milling promotes fast fracturing, recrystallization, mineral reduction and solid-solid reactions.