铜催化芳杂环C-H键区域选择性芳基化的研究进展

铜作为一种廉价、新型的芳环C-H键官能团化反应催化剂,近年来一直是有机化学和催化化学的研究热点和难点之一.依据参与反应的底物的不同,综述近年来文献报道的铜催化芳杂环C-H键区域选择性芳基化反应及其机理的最新研究进展.     

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.     

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.     

Natural products as inspiration for the development of asymmetric catalysis

Biologically active natural products often contain particularly challenging structural features and functionalities in terms of synthesis. Perhaps the greatest difficulties are those caused by issues of stereochemistry. A useful strategy for synthesizing such molecules is to devise methods of bond formation that provide opportunities for using enantioselective catalysis. In using this tactic, the desire for a particular target structure ultimately drives the development of catalytic methods. New enantioselective catalytic methods contribute to a greater fundamental understanding of how bonds can be constructed and lead to valuable synthetic technologies that are useful for a variety of applications.     

Structure modification of unsaturated natural products:The epoxidation of carbon-carbon double bonds in some natural products with hydrogen peroxide catalyzed by iodine

Aim To afford an environmentally benign catalytic epoxidation of carbon-carbon double bonds in organic substrates using hydrogen peroxide as an oxidant and iodine as a catalyst.Method The effects of di...     

Sn-zeolite beta as a heterogeneous chemoselective catalyst for Baeyer-Villiger oxidations

The Baeyer-Villiger oxidation, first reported more than 100 years ago, has evolved into a versatile reaction widely used to convert ketones-readily available building blocks in organic chemistry-into more complex and valuable esters and lactones. Catalytic versions of the Baeyer-Villiger oxidation are particularly attractive for practical applications, because catalytic transformations simplify processing conditions while minimizing reactant use as well as waste production. Further benefits are expected from replacing peracids, the traditionally used oxidant, by cheaper and less polluting hydrogen peroxide. Dissolved platinum complexes and solid acids, such as zeolites or sulphonated resins, efficiently activate ketone oxidation by hydrogen peroxide. But these catalysts lack sufficient selectivity for the desired product if the starting material contains functional groups other than the ketone group; they perform especially poorly in the presence of carbon-carbon double bonds. Here we show that upon incorporation of 1.6 weight per cent tin into its framework, zeolite beta acts as an efficient and stable heterogeneous catalyst for the Baeyer-Villiger oxidation of saturated as well as unsaturated ketones by hydrogen peroxide, with the desired lactones forming more than 98% of the reaction products. We ascribe this high selectivity to direct activation of the ketone group, whereas other catalysts first activate hydrogen peroxide, which can then interact with the ketone group as well as other functional groups.     

壳聚糖负载钯催化剂的制备及其在偶联反应中的应用

壳聚糖是一种来源丰富、价格低廉、无毒无害,易降解,环境友好型的天然高分子材料。壳聚糖分子结构中具有大量的羟基与氨基等功能性基团,与金属具有优异的配位能力,完全可以替代合成高分子作为金属催化剂的载体。直接以天然高分子壳聚糖为载体,在酸性条件下采用二氯化钯进行负载,制备壳聚糖负载钯催化剂,对其进行结构表征,并将其应用于催化Suzuki偶联反应,结果表明壳聚糖负载钯催化剂具有优良的催化性能和循环使用性能。     

Design and Synthesis of Structurally Well-Defined Functional Polyolefins via Transition Metal-Mediated Olefin Polymerization Chemistry

1 IntroductionIn fact, ever since the commercialization of PE and PP in the 1950s, the functionalization of polyolefins has been a very interesting research subject attracting attentions from both academic and industrial communities. The so-called polyolefin functionalization is explained as introducing polar functional groups into polyolefins. With the precondition of maintaining the desired properties of polyolefins, polyolefin functionalization confers reactivity to polyolefins, improving…     

从芳香性碳-碳双键的反应特性阐述碳纳米管功能化修饰

 纳米材料的功能化修饰构成了现代纳米技术的重要组成部分。作为纳米材料的成员之一,碳纳米管不易分散或溶解于任何溶剂。为了改善碳纳米管的分散/溶解性能,对其进行必要的化学修饰是可行的途径。构成碳纳米管的芳香性碳-碳双键是其功能化修饰主体。利用有机化学碳-碳双键反应的基本理论知识,能指导碳纳米管的修饰,并可预测碳纳米管的形貌及电子性能改变规律。而碳纳米管的功能化修饰成果,也有助于增强难溶有机化合物的碳-碳双键反应特性和规律的理论基础。本文从近年的科研成果出发,从结构-性能角度深入探讨了不同修饰方法对碳纳米管形貌及结构的影响。基于碳-碳双键的加成反应有效保持了原始碳纳米管的形貌,更有利于修饰碳纳米管的广泛应用。     

Prins成环反应研究最新进展

Prins反应作为有机合成中一个经典的碳碳键构成方法，近来重新引起有机合成化学工作者的重视，尤其是分子内Prins成环反应具有非常大的合成价值，作者整理和总结了近几年来对该反应的文献报道，包括反应的催化体系、反应选择性、相关合成方法学、反应机理以及在复杂天然产物分子合成中的应用等多方面所取得的重要进展。     

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.     

2-羟基喹啉合成新方法研究

本研究利用简单的乙酰苯胺和丙烯酸酯作为起始原料,在过硫酸钾做氧化剂,水合对甲苯磺酸做添加剂的条件下,通过钯催化的C-H键活化/C-C键生成/环化串联反应以46%~95%收率合成了一系列2-羟基喹啉衍生物.本研究为2-羟基喹啉衍生物的合成提供了实用的合成方法.     

药物中间体β-卤代苯乙胺的简便合成

发展了一条高效、简单的药物中间体β-卤代苯乙胺的合成方法.二苄胺和溴乙酸乙酯作为起始原料,经历取代、加成、催化氢化、氯代和酰化5步反应,以中等产率制备得到目标产物2-乙酰氨基-3-氯-3-(4-甲氧基苯基)丙酸乙酯,对合成过程中的中间产物及目标产物的制备进行了条件优化,确定了最佳反应路线,同时还通过熔点、核磁共振氢谱和碳谱对目标产物进行了表征.此合成方法为含多官能化苯乙胺结构的药物分子的合成提供了一种便利途径.     

Synthesis of macrocyclic natural products by catalyst-controlled stereoselective ring-closing metathesis

Many natural products contain a C = C double bond through which various other derivatives can be prepared; the stereochemical identity of the alkene can be critical to the biological activities of such molecules. Catalytic ring-closing metathesis (RCM) is a widely used method for the synthesis of large unsaturated rings; however, cyclizations often proceed without control of alkene stereochemistry. This shortcoming is particularly costly when the cyclization reaction is performed after a long sequence of other chemical transformations. Here we outline a reliable, practical and general approach for the efficient and highly stereoselective synthesis of macrocyclic alkenes by catalytic RCM; transformations deliver up to 97% of the Z isomer owing to control induced by a tungsten-based alkylidene. Utility is demonstrated through the stereoselective preparation of epothilone C (refs 3-5) and nakadomarin A (ref. 6), the previously reported syntheses of which have been marred by late-stage, non-selective RCM. The tungsten alkylidene can be manipulated in air, delivering the products in useful yields with high stereoselectivity. As a result of efficient RCM and re-incorporation of side products into the catalytic cycle with minimal alkene isomerization, desired cyclizations proceed in preference to alternative pathways, even under relatively high substrate concentration.     

钯碳催化剂在硝基还原和碳碳双键加氢反应中的应用

对常温常压下钯碳催化剂在精细有机合成中的硝基还原和碳碳双键加氢两大类加氢反应进行了初步的探索，２－氯－６－硝基甲苯在钯碳催化剂存在下催化还原，除目的产物外，不生成脱氯副产物。这是一个连串反应，控制反应条件可获得较高的反应选择性。     

焦化蜡油中芳香分的催化裂化特性及其对饱和分裂化性能的阻滞作用

采用糠醛抽提,从焦化蜡油(CGO)中抽提分离出芳香分,考察芳香分的催化裂化反应特性及其对饱和分催化裂化反应性能的阻滞作用。结果表明:糠醛对CGO中的芳烃具有较好的抽提效果,减弱了稠环芳烃对饱和烃的竞争吸附和对其反应的阻滞作用,使CGO抽余油的催化裂化性能明显优于CGO原料油,转化率提高了15.3个百分点,而芳烃抽出油的转化率比CGO原料油降低了16.1个百分点;剂油比对提高芳烃抽出油转化率和目的产品收率的效果最为显著,质量空速的效果次之,而反应温度的效果最差;芳烃抽出油不仅本身很难催化裂化,而且还阻碍了饱和分的有效催化转化,从而使原料的转化率下降,目的产品收率降低,焦化蜡油中的多环或稠环芳烃是制约其有效催化转化的关键因素之一。     

酸改性高岭土催化合成乳酸正丁酯的研究

研制了盐酸改性高岭土催化剂，并用其催化合成乳酸正丁酯，讨论了催化剂用量、催化时间以及酸醇配比对乳酸转化率的影响，实验表明盐酸改性高岭土催化剂对乳酸正丁酯的合成具有催化活性高、催化剂容易回收，价格低廉等优点。     

生物柴油多组分替代混合物化学反应路径分析

采用MD、MD9D和正庚烷三组分作为生物柴油混合替代物,替代物机理包含3 299种组分、10 806个基元反应。应用CHEMKIN-PRO反应速率分析法对燃烧氧化过程中燃料分子高低温主要反应路径和重要中间组分衍化过程进行了详细探究。结果表明:MD和MD9D在低温阶段主要通过脱氢加氧、异构化反应以及酮类物质的分解反应进行消耗,高温阶段主要是低温反应中间产物C—O、C—C键β分解反应、部分高温脱氢以及异构化反应最终生成C_2H_4等小分子产物。另外,MD和MD9D中不同碳原子位置C—H键能不同,邻近羧基以及C≡C双键碳原子处C—H键较弱,易发生脱氢反应生成烷酯基。在过氧酯基异构化生成过氧羧酯基过程中,不同环数过渡环张力大小以及反应势垒不同,异构化难易程度不同,而六元过渡环的张力较小,反应势垒较低,最易发生异构化反应,异构化反应产物更多。     

镍催化卤代烷烃交叉偶联反应的配体忧化

两个结构相似的卤代烷烃直接经过镍催化还原偶联反应生成新的 C(sp³ )—C(sp³ ) 键 一直是有机合成中的难点. 通过前期的研究发现, 采用 Zn 作还原剂, Ni(cod)₂ 作催化剂, 在 Pybox 类配体存在的条件下, 可以成功地实现不同卤代烷烃的交联反应, 不过其中一个卤代烷烃必须使用 3 mol 的用量. 为了进一步提高反应的效率, 采用 2 mol 的 1-溴丁烷和 1 mol 的 4-溴-1-对甲苯磺酰基哌啶为模型进行反应, 通过优化反应条件, 特别是对配体结构的修饰, 进一步提高不活泼烷基卤代物的还原交叉偶联反应效率. 研究结果表明, Pybox 类配体是效果较好的配体, 而二齿配体在吡啶存在的条件下也能得到中等期望值的产率. 这一结果为今后进一步优化反应提供了参考依据.     

Carbon-heteroatom bond formation catalysed by organometallic complexes

At one time the synthetic chemist's last resort, reactions catalysed by transition metals are now the preferred method for synthesizing many types of organic molecule. A recent success in this type of catalysis is the discovery of reactions that form bonds between carbon and heteroatoms (such as nitrogen, oxygen, sulphur, silicon and boron) via complexes of transition metals with amides, alkoxides, thiolates, silyl groups or boryl groups. The development of these catalytic processes has been supported by the discovery of new elementary reactions that occur at metal-heteroatom bonds and by the identification of factors that control these reactions. Together, these findings have led to new synthetic processes that are in daily use and have formed a foundation for the development of processes that are likely to be central to synthetic chemistry in the future.