Synthesis, characterization and properties of diamidodisilanes and azocyclosilane

Organosilicon compounds have been widely researched and have the maximum species besides hydrocarbons. In the progress of the research work, many scientists pay attention to the organic silicon compounds that have vari-ety reactive functional groups[1,2]. The difunctional disi-lanes are very active; they could react with not only the compounds containing reactive hydrogen atoms, but also the reactive polymers. Therefore, the disilanes with di-functional groups could be used as disilane substit…     

单核和双核过渡金属羰基化合物及双核过渡金属羰基夹心化合物的理论研究

用量子化学理论方法研究了一系列过渡金属羰基化合物及第一长周期双核过渡金属羰基夹心化合物.根据理论研究结果,对一些早期有关过渡金属羰基化合物的实验结论提出了质疑,对一些同族过渡金属元素原子形成的羰基化合物的结构和成键规律进行了探讨;对第一长周期过渡金属双核羰基夹心化合物进行的理论研究表明,不饱和程度较高的V2 (CO)n...     

Catalytic functionalization of unactivated primary C-H bonds directed by an alcohol

New synthetic methods for the catalytic functionalization of C-H bonds have the potential to revolutionize the synthesis of complex molecules. However, the realization of this synthetic potential requires the ability to functionalize selectively one C-H bond in a compound containing many such bonds and an array of functional groups. The site-selective functionalization of aliphatic C-H bonds is one of the greatest challenges that must be met for C-H bond functionalization to be used widely in complex-molecule synthesis, and processes catalysed by transition-metals provide the opportunity to control selectivity. Current methods for catalytic, aliphatic C-H bond functionalization typically rely on the presence of one inherently reactive C-H bond, or on installation and subsequent removal of directing groups that are not components of the desired molecule. To overcome these limitations, we sought catalysts and reagents that would facilitate aliphatic C-H bond functionalization at a single site, with chemoselectivity derived from the properties of the catalyst and site-selectivity directed by common functional groups contained in both the reactant and the desired product. Here we show that the combination of an iridium-phenanthroline catalyst and a dihydridosilane reagent leads to the site-selective γ-functionalization of primary C-H bonds controlled by a hydroxyl group, the most common functional group in natural products. The scope of the reaction encompasses alcohols and ketones bearing many substitution patterns and auxiliary functional groups; this broad scope suggests that this methodology will be suitable for the site-selective and diastereoselective functionalization of complex natural products.     

一种新型含二茂铁基三角架配体的合成与表征

近年来,杂氮三角架型化合物及其过渡金属配合物的合成引起了人们的广泛兴趣［１,２］,三角架配体与金属离子形成的配合物具有高度的热力学稳定性和动力学惰性,并且该类配体能作为合成许多大环化合物的前体物质．二茂铁基团由于具有芳香性、可逆的氧化还原性、稳定性及低毒性,其衍生物在聚合物、电化学、医学等领域有着广泛的应用．将二茂铁基引入不同的分子,以期得到新的具有特殊性能的化合物是近年来研究的热点［３,４］．通过二茂铁甲酰肼与三角架醛的缩合反应,得到一种新型三角架配体三｛［２（２苯甲醛二茂铁甲酰腙）氧代…     

Superconductivity in molecular crystals induced by charge injection

Progress in the field of superconductivity is often linked to the discovery of new classes of materials, with the layered copper oxides being a particularly impressive example. The superconductors known today include a wide spectrum of materials, ranging in complexity from simple elemental metals, to alloys and binary compounds of metals, to multi-component compounds of metals and chalcogens or metalloids, doped fullerenes and organic charge-transfer salts. Here we present a new class of superconductors: insulating organic molecular crystals that are made metallic through charge injection. The first examples are pentacene, tetracene and anthracene, the last having the highest transition temperature, at 4 K. We anticipate that many other organic molecular crystals can also be made superconducting by this method, which will lead to surprising findings in the vast composition space of molecular crystals.     

Chemical space and biology

Chemical space--which encompasses all possible small organic molecules, including those present in biological systems--is vast. So vast, in fact, that so far only a tiny fraction of it has been explored. Nevertheless, these explorations have greatly enhanced our understanding of biology, and have led to the development of many of today's drugs. The discovery of new bioactive molecules, facilitated by a deeper understanding of the nature of the regions of chemical space that are relevant to biology, will advance our knowledge of biological processes and lead to new strategies to treat disease.     

Large-scale prediction and testing of drug activity on side-effect targets

Discovering the unintended 'off-targets' that predict adverse drug reactions is daunting by empirical methods alone. Drugs can act on several protein targets, some of which can be unrelated by conventional molecular metrics, and hundreds of proteins have been implicated in side effects. Here we use a computational strategy to predict the activity of 656 marketed drugs on 73 unintended 'side-effect' targets. Approximately half of the predictions were confirmed, either from proprietary databases unknown to the method or by new experimental assays. Affinities for these new off-targets ranged from 1 nM to 30 μM. To explore relevance, we developed an association metric to prioritize those new off-targets that explained side effects better than any known target of a given drug, creating a drug-target-adverse drug reaction network. Among these new associations was the prediction that the abdominal pain side effect of the synthetic oestrogen chlorotrianisene was mediated through its newly discovered inhibition of the enzyme cyclooxygenase-1. The clinical relevance of this inhibition was borne out in whole human blood platelet aggregation assays. This approach may have wide application to de-risking toxicological liabilities in drug discovery.     

神奇材料与2000年诺贝尔化学奖

讨论了神奇材料——导电聚合物又称“合成金属”的发现与 2 0 0 0年诺贝尔化学奖的关系 ,介绍了导电聚合物的广泛应用及其前景 ,说明了这一伟大发明是科学家通力合作研究的结晶 ,对美国科学家艾伦·黑格 (Alan Jay Heeger,1 936 -) ,艾伦·马克迪尔米德 (Alan Graham Mac Diarmid,1 92 7-)和日本科学家白川英树 (Shirakawa Hideki,1 936 -)授予 2 0 0 0年诺贝尔化学奖 ,也是对从事导电聚合物研究领域内所有科学家研究成果的肯定与认可 ,这一领域将是未来十分活跃的新材料研究领域     

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.     

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。     

Biomimetic, Catalytic Oxidation in Organic Synthesis

1 Introduction Oxidation is one of the most fundamental reactions in organic synthesis. Owing to the current need to develop forward-looking technology that is environmentally acceptable with respect many aspects. The most attractive approaches are biomimetic oxidation reactions that are closely related to the metabolism of living things. The metabolisms are governed by a variety of enzymes such as cytochrome P-450 and flavoenzyme. Simulation of the function of these enzymes with simple trans…     

Systematic design of chemical oscillators using complexation and precipitation equilibria

Concentration oscillations are ubiquitous in living systems, where they involve a wide range of chemical species. In contrast, early in vitro chemical oscillators were all derived from two accidentally discovered reactions based on oxyhalogen chemistry. Over the past 25 years, the use of a systematic design algorithm, in which a slow feedback reaction periodically drives a bistable system in a flow reactor between its two steady states, has increased the list of oscillating chemical reactions to dozens of systems. But these oscillating reactions are still confined to a handful of elements that possess multiple stable oxidation states: halogens, sulphur and some transition metals. Here we show that linking a 'core' oscillator to a complexation or precipitation equilibrium can induce concentration oscillations in a species participating in the equilibrium. We use this method to design systems that produce periodic pulses of calcium, aluminium or fluoride ions. The ability to generate oscillations in elements possessing only a single stable oxidation state (for example, Na+, F-, Ca2+) may lead to reactions that are useful for coupling to or probing living systems, or that help us to understand new mechanisms by which periodic behaviour may arise.     

Catalytic C-H functionalization by metal carbenoid and nitrenoid insertion

Novel reactions that can selectively functionalize carbon-hydrogen bonds are of intense interest to the chemical community because they offer new strategic approaches for synthesis. A very promising 'carbon-hydrogen functionalization' method involves the insertion of metal carbenes and nitrenes into C-H bonds. This area has experienced considerable growth in the past decade, particularly in the area of enantioselective intermolecular reactions. Here we discuss several facets of these kinds of C-H functionalization reactions and provide a perspective on how this methodology has affected the synthesis of complex natural products and potential pharmaceutical agents.     

Understanding and exploiting C-H bond activation

The selective transformation of ubiquitous but inert C H bonds to other functional groups has far-reaching practical implications, ranging from more efficient strategies for fine chemical synthesis to the replacement of current petrochemical feedstocks by less expensive and more readily available alkanes. The past twenty years have seen many examples of C-H bond activation at transition-metal centres, often under remarkably mild conditions and with high selectivity. Although profitable practical applications have not yet been developed, our understanding of how these organometallic reactions occur, and what their inherent advantages and limitations for practical alkane conversion are, has progressed considerably. In fact, the recent development of promising catalytic systems highlights the potential of organometallic chemistry for useful C-H bond activation strategies that will ultimately allow us to exploit Earth's alkane resources more efficiently and cleanly.     

Formation of thermally stable alkylidene layers on a catalytically active surface

Materials containing organic-inorganic interfaces usually display a combination of molecular and solid-state properties, which are of interest for applications ranging from chemical sensing to microelectronics and catalysis. Thiols--organic compounds carrying a SH group--are widely used to anchor organic layers to gold surfaces, because gold is catalytically sufficiently active to replace relatively weak S-H bonds with Au-S bonds, yet too inert to attack C-C and C-H bonds in the organic layer. But although several methods of functionalizing the surfaces of semiconductors, oxides and metals are known, it remains difficult to attach a wide range of more complex organic species. Organic layers could, in principle, be formed on the surfaces of metals that are capable of inserting into strong bonds, but such surfaces catalyse the decomposition of organic layers at temperatures above 400 to 600 K, through progressive C-H and C-C bond breaking. Here we report that cycloketones adsorbed on molybdenum carbide, a material known to catalyse a variety of hydrocarbon conversion reactions, transform into surface-bound alkylidenes stable to above 900 K. We expect that this chemistry can be used to create a wide range of exceptionally stable organic layers on molybdenum carbide.     

LB膜分子系统及其性能

尽管LB膜还存在着很多待研究的问题,尚不能予以广泛地应用,但是LB技术较之其它有机薄膜的形成方法却有许多优越性,有助于新型材料的研制,因此越来越多的科学家对此产生了浓厚的兴趣,做了大量的工作,使得人们对此领域有了更进一步的认识。本文将LB膜的一些重要性质作了概括,其中包括单分子膜的形成、累积单分子膜中的能量转移及化学反应等。     

离子液体及其在过渡金属催化反应中的应用

介绍了离子液体的基本性质和常用的合成方法,着重介绍了十几年来离子液体在过渡金属催化反应中的应用进展.     

咪唑环卡宾钯配合物参与的偶联反应新进展

钯催化交叉偶联反应可高效构建碳-碳键、碳-杂键等复杂结构单元,应用十分广泛。除了传统的膦配体催化体系外,新兴的氮杂环卡宾催化体系已在多种偶联反应中得到成功的应用。目前针对该催化体系的研究主要集中于新氮杂环卡宾配体结构的构建、新辅助配体的配合使用以及新反应体系的开发等。氮杂环卡宾参与的偶联反应也越来越向着绿色、可持续的方向发展。结合最新的文献报道,针对咪唑环类氮杂环卡宾配合物在上述方向的发展进行详细评述。     

初始条件对Ga冷凝过程影响的模拟研究

对液态金属快速凝固过程进行了分子动力学模拟研究.以1000个液态纯金属Ga原子的系统为例,深入考察了微观结构组态的变化.采用H-A键型指数法分析该过程中各种键的变化情况.发现在其微观结构的转变过程中,与二十面体及其缺陷结构密切相关的1551键型起着重要的作用,同时,还发现不同的初始平衡态对其固态微结构有明显的影响,这-结果对于深入理解液-固微结构之间的转变关系,具有一定的理论和实际意义.