有机小分子催化ε-己内酯开环聚合反应

聚己内酯(PCL)是一种生物可降解高分子材料,具有良好的环境、生物相容性,广泛应用于生物医学、包装等领域。有机小分子催化ε-己内酯单体开环聚合反应是制备聚己内酯的主要方式之一。与传统的金属催化相比,有机催化不仅反应条件温和、聚合可控,而且还可解决聚合物中金属残留问题,是目前高分子合成化学的研究热点。本文按照催化体系的不同活化方式,讨论了近年来有机催化在ε-己内酯开环聚合反应中的研究进展,归纳总结了不同催化体系的优缺点,并在此基础上展望了有机小分子催化剂在ε-己内酯开环聚合反应中的发展趋势和应用前景。     

有机小分子催化ε-己内酯开环聚合反应

聚己内酯(PCL)是一种生物可降解高分子材料,具有良好的环境、生物相容性,广泛应用于生物医学、包装等领域。有机小分子催化ε-己内酯单体开环聚合反应是制备聚己内酯的主要方式之一。与传统的金属催化相比,有机催化不仅反应条件温和、聚合可控,而且还可解决聚合物中金属残留问题,是目前高分子合成化学的研究热点。本文按照催化体系的不同活化方式,讨论了近年来有机催化在ε-己内酯开环聚合反应中的研究进展,归纳总结了不同催化体系的优缺点,并在此基础上展望了有机小分子催化剂在ε-己内酯开环聚合反应中的发展趋势和应用前景。     

基于Bergman环化反应的高分子合成方法

高分子合成化学是高分子科学的基础,高效的聚合反应是合成高分子材料的关键.Bergman环化反应是一种可以形成芳香双自由基活性物质的化学过程.芳基双自由基可以快速偶联形成聚芳烃,为此类聚合物的合成提供简洁的方法.本文系统地介绍了Bergman环化反应进入高分子科学后的发展轨迹,阐述了我们研究组利用该反应的原位聚合机制以及不需要催化剂不产生副产物的特点,在明确该反应的聚合反应机理的基础上,建立了线形聚合物、聚合物粒子、面形聚合物等具有多种特殊拓扑结构形貌以及功能的聚合物纳米材料的工作.最后,对Bergman环化反应中尚存在的问题进行总结并对其未来在高分子科学中的发展予以展望.     

Baeyer-Villiger氧化反应的不同催化体系

Baeyer-Villiger氧化反应能控制产物的立体化学结构,在有机合成中对功能基转化和环扩张有重要的意义,因此氧化所得的产物可以广泛应用于合成许多天然产物和药物中间体以及一些高分子材料的单体等,是目前有机化学研究的热点之一。随着对该反应研究的深入,其催化剂的类型也在不断地增多,包括均相催化剂、非均相催化剂、生物催化剂。均相催化剂选择性和转化率虽高,但不及非均相催化剂重复利用率高。生物催化剂绿色环保,是未来研究的重点之一。本文从均相催化、非均相催化和生物催化三个方面对Baeyer-Villiger氧化反应相关的研究新进展进行了阐述,重点介绍了不同催化体系下催化剂与反应底物之间的作用,总结了有关催化反应的机理,并对Baeyer-Villiger氧化反应的发展进行了展望。     

稀土络合催化剂的最新进展

众所周知,本世纪五十年代Ziegler-Natta催化剂的发现揭开了高分子研究领域的新篇章.三十多年来,这种催化剂不仅合成了许多新型的聚合物,而且某些品种已实现了大规模工业化生产.其中,低压聚乙烯、聚丙烯、乙丙橡胶、顺丁橡胶和异戊橡胶成为重要的合成高分子材料,为世人所注目.近年来,由于各国科学工作者的共同努力,Ziegler-Natta催化剂得到了不断的发展和完善.新型载体催化剂的出现,使催化效率大为提高,新的聚合物和催化体系不断地涌现.与此同时,催化聚合机理的研究也取得新的进展.关于Ziegler-Natta催化剂发展的情况,John Boor已有专著出版,该书总结了七十年代以前Ziegler-Natta催化剂发展的概况,但对近年来载体催化剂的进展及其它新出现的催化体系没有予以     

高分子支载手性催化剂在Michael反应中的研究进展

高分子手性催化剂用于不对称有机合成,它易与产物分离、可通过适当的处理后回收重复使用;具有毒性或气味的手性催化剂支载在高分子上后,使用更加安全和方便;而且,适当结构的高分子聚合物可以为不对称反应提供更有利的微环境,提高立体选择性.正是这些优点,高分子手性催化剂的研究越来越受到人们的关注.不对称Michael反应是形成手性碳-碳、碳-杂键的重要反应,在有机合成和药物合成中起着重要的作用.本文综述了近年来的高分子手性催化剂在Michael反应中的应用及最新进展.     

有机小分子催化合成高聚物的研究进展

综述了有机小分子催化剂在高分子合成上应用的研究进展,着重分析催化剂结构与催化效能、单体的选择性以及聚合物的性质之间的关系。     

高分子负载苯并噻唑鎓盐的制备及其催化反应

高分子负载试剂和催化剂在有机合成中已得到广泛应用.前文我们报道了苯并噻唑鎓盐催化合成1,4-二羰基化合物的反应,发现反应中鎓盐活性有衰减.张标宏等用20%交联聚苯乙烯负载 Stetter 催化剂曾获较好结果.本文拟报道高分子苯并噻唑鎓盐的制备及其催化反应.     

高分子载体Lewis酸催化剂:苯乙烯、丙烯腈共聚物-四氯化钛复合物

高分子催化剂是功能性高分子的重要组成部分,是目前催化剂研究的方向之一,近年来发展很快。我们曾将在空气中强烈水解的Lewis酸四氯化钛与聚苯乙烯反应制备了一种比较稳定的复合物,它对酯化、缩醛、缩酮等有机反应具有良好的催化效能,也可作为α-甲基苯乙烯正离子聚合的有效催化剂,在室温下即可获得高分子量的聚合物。为了进一步改进其稳定性和重复使用性能,本文合成了一种苯乙烯与丙烯脂的共聚交联小球,然后与四氯化钦反应制成了一种更加稳定的高分子载体Lewis酸催化剂,它不但对醋化、缩醛、缩酮等有机反应有很高的催化活性,而且重复使用性能大为改善,是一种很有希望应用于实际的高分子催化剂。     

酯酶在化学合成中的应用进展

酯酶对于水解、酯化和转酯化等反应具有高活性和立体选择性,其生产成本低于脂肪酶,因而酯酶用作化学合成的催化剂,将使生物催化合成成本更低。分析了酯酶在分子合成中的催化性质,对酯酶催化手性分子和聚合物的合成及其固定化进行了总结和评述,并对其催化作用在化学合成方面的应用发展进行了展望。     

From regulation of elementary stages of radical processes to controlled synthesis of macromolecules

Recent published data on the regulation of the elementary stages of homolytic reactions involving radical species are analyzed in the review. The special focus is made on the application of metal complex compounds to mediating radical reactions and their use in the processes of the controlled synthesis of macromolecules, including functional homo- and copolymers, and also nano-sized polymer structures. Examples are considered and prospects are estimated of the practical application of the reversible inhibition of radical processes, reversible chain transfer, atom transfer reactions involving radicals and metal complexes under industrial conditions, in particular, for the production of polymer high tech materials.     

Progress in controlled polymerization and design of novel polymer architectures

Recent developments of new synthetic methods are stimulating the design of new polymers. Modern generations of highly active and selective transition metal catalysts give excellent control on molecular weight, regio- and stereoregularities, long- and short-chain-branching, polymer crystallization, and morphology of olefin, diene, cyclolefin, and styrene polymers. Ethene is copolymerized with polar comonomers such as carbon monoxide and acrylates in new low pressure processes. Catalytic coupling reactions of aromatic halogen compounds and bisphenols afford rigid polyarylenes. „Living” radical polymerization (“TEMPO” and “ATRP”) produce a wide range of telechelics, block copolymers and cascade macromolecules. In reactive processing oxazoline-mediated coupling reactions are the key to melt diversification of well-known polymers. Supramolecular concepts are being applied to tailor hybrid polymers and nanocomposites. Precision in polymer synthesis is the key to new materials with wide application range.     

Transition-metal-catalyzed dehydrocoupling: a convenient route to bonds between main-group elements

The development of transition-metal-catalyzed dehydrocoupling reactions as a synthetic method for the formation of main-group element-element bonds provides an increasingly attractive and convenient alternative to traditional routes such as salt metathesis/elimination-type reactions. Since the first reported examples in the early 1980s, there has been a rapid expansion of this field, with extensions to a wide variety of metal-mediated homonuclear and heteronuclear bond-forming processes. Applications of this new chemistry in molecular and polymer synthesis, materials science, hydrogen storage and the transfer hydrogenation of organic substrates are attracting growing attention. An overview of this emerging area is presented in this Concepts article with a focus on recent results.     

Nitroxides: applications in synthesis and in polymer chemistry

This Review describes the application of nitroxides to synthesis and polymer chemistry. The synthesis and physical properties of nitroxides are discussed first. The largest section focuses on their application as stoichiometric and catalytic oxidants in organic synthesis. The oxidation of alcohols and carbanions, as well as oxidative C-C bond-forming reactions are presented along with other typical oxidative transformations. A section is also dedicated to the extensive use of nitroxides as trapping reagents for C-centered radicals in radical chemistry. Alkoxyamines derived from nitroxides are shown to be highly useful precursors of C-centered radicals in synthesis and also in polymer chemistry. The last section discusses the basics of nitroxide-mediated radical polymerization (NMP) and also highlights new developments in the synthesis of complex polymer architectures.     

Membranes of high performance polymers

Membranes, as part of technical processes, are gaining more importance in areas such as chemicals, biotechnology or waste-water treatment. The use of high performance polymers as membrane materials offers unique combinations of properties and allows new applications. Three different approaches towards membrane fabrication from high performance polymers such as polyaryls or polyaramides are discussed, i. e. maintenance of the polymer structure during processing and synthesis of better soluble structures via either polymer-analogous reactions or tailor-made copolymers. Examples of chemistry, property profiles and potential applications are given.     

Methods for the synthesis of uniform polymers

The difficulties encountered in the preparation of polymers that are uniform chemically, structurally, and in their molecular weight are due mainly to the wide variety of possible polymers. This arcticle gives a review of attempts to synthesize homogeneous polymers by chain reactions and by stepwise synthesis. Syntheses on templates are extremely important in living cells; methods have recently been found for syntheses of this type that are independent of natural processes. Uniform polymers can also be obtained by reactions on existing polymers. In replicating polymers, this in principle requires the modification of only one polymer molecule.     

Flow fine synthesis with heterogeneous catalysts

In the past few decades, organic reactions under flow conditions have attracted increasing attention. Flow reactions have a number of advantages over batch reactions in terms of environmental compatibility, efficiency, and safety. In particular, flow reactions with heterogeneous catalysts that yield desired products without significant levels of by-product formation can enable purification processes to be avoided. This feature can allow flow reactions to be assembled in a multi-step and continuous manner for the synthesis of complex molecules. These new techniques have opened up new approaches to the synthesis of fine chemicals and are expected to play a prominent role in future chemical manufacturing processes. In this context, this review aims to summarize recent developments in continuous-flow reactions with heterogeneous catalysts for synthesis of fine chemicals.     

Palladium-catalyzed cross-coupling reactions in total synthesis

In studying the evolution of organic chemistry and grasping its essence, one comes quickly to the conclusion that no other type of reaction plays as large a role in shaping this domain of science than carbon-carbon bond-forming reactions. The Grignard, Diels-Alder, and Wittig reactions are but three prominent examples of such processes, and are among those which have undeniably exercised decisive roles in the last century in the emergence of chemical synthesis as we know it today. In the last quarter of the 20th century, a new family of carbon-carbon bond-forming reactions based on transition-metal catalysts evolved as powerful tools in synthesis. Among them, the palladium-catalyzed cross-coupling reactions are the most prominent. In this Review, highlights of a number of selected syntheses are discussed. The examples chosen demonstrate the enormous power of these processes in the art of total synthesis and underscore their future potential in chemical synthesis.     

高分子材料的应力诱导反应

本文是作者所在科学研究群体借助超声波、高速搅拌、微波和研磨应力诱导反应制备一些难以用一般方法合成的嵌段／接枝共聚物和高分子纳米材料,探索高分子材料高性能化高效途径等方面研究工作简介。     

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.