微波辅助合成菲并咪唑衍生物及微波非热效应

以1,10-邻菲啰啉5,6-二酮及苯甲醛(或取代苯甲醛)为原料, 在微波辐射条件下制备了一系列菲并咪唑类衍生物, 考察了温度、 时间以及投料比对微波辅助合成菲并咪唑类衍生物的影响, 并进一步探讨了微波非热效应的影响. 设计正交实验优化了反应条件; 使用SiC管作为反应容器屏蔽微波对反应的影响; 通过元素分析、 核磁共振波谱、 质谱及红外光谱等对化合物进行了表征. 结果表明, 微波辅助反应的最佳反应条件为: 1,10-邻菲啰啉-5,6-二酮与苯甲醛(或取代苯甲醛)的投料比为1: 1.5, 反应温度为100℃, 反应时间为20 min; 并且发现SiC管中反应的产率明显低于石英管反应容器. 与传统制备方法相比, 微波辅助合成方法可在更短时间内快速方便地制得菲并咪唑类衍生物; 反应温度、 反应时间以及投料比对微波辅助合成反应有明显影响; 微波非热效应有助于提高反应产率.     

微波合成氨基甲酸酯型脱氧胆酸分子钳及其分子识别性能

用脱氧胆酸甲酯和三光气为原料,微波辐射作用下在脱氧胆酸甲酯3位反应生成酰氯后,继续在微波辐射作用下与各种芳胺反应,合成了10个新的氨基甲酸酯型脱氧胆酸分子钳人工受体,产率79~95%,其结构经质谱、红外、核磁和元素分析表征。用UV-Vis方法初步研究了分子钳4a~4j对客体中性分子的识别性能。结果表明,分子钳4a~4j对所考察的中性分子显示良好的识别作用,分子钳与中性分子间形成1∶1型主客体络合物,除分子钳4c外,识别顺序皆为:苯胺邻甲氧苯胺间甲氧苯胺对甲氧苯胺。     

双膦酸化合物对基质金属蛋白酶的抑制效应及机理

根据基质金属蛋白酶(MMPs)的活性位点附近三维空间结构, 设计合成了4种双膦酸类化合物, 利用酶促反应动力学方法对比测试了双膦酸化合物及阿伦磷酸钠(Alendronate)对MMPs的抑制效果; 结合分子对接方法以及荧光滴定光谱研究了双膦酸化合物与MMPs的分子识别和作用机理, 并得到了二者的结合模型.     

微波技术在钯催化Suzuki-Miyaura交叉偶联反应中的应用研究进展

与传统的加热方图式相比,微波加热具有加热速度快、热效率高、节约能源、洁净、操作简单等优点,已成为重要的有机合成工具之一.钯催化的Suzuki-Miyaura交叉偶联反应提供了一种合成各种联芳烃的温和方法,具有较好的选择性,受到了合成化学家的广泛关注.综述了近年来微波技术在钯催化的Suzuki-Miyaura交叉偶联反应中的应用研究进展,包括多种反应体系,并对其在天然产物和生物活性分子合成中的应用作简要概述.     

<有机合成化学及近代技术>简介

由徐家业主编、西北工业大学出版社出版(1997)的<有机合成化学及近代技术>与流行的同类书籍通常偏重于介绍有机合成反应或各类有机化合物的合成方法不同.该书在按化合物的分子骨架构成,和官能团的变换为纲简要地介绍有机合成反应的同时,较全面的介绍了各种近代有机合成方法和技术.包括有机合成设计、有机电化学合成、相转移催化技术、固相合成方法和干法合成等.除了通常的加热促进反应之外,还介绍了光促反应、微波促进反应和声波促进反应,以及生物催化剂的应用和仿生合成法等,展示了有机合成的新面貌.针对有机合成的实用性,还特意编写了"有机合成的化工过程开发"一章,是一本别具风格的有机化学参考书.     

微波技术在催化剂制备中的应用

微波作为一种独特的加热手段在化学领域已得到广泛应用。本文综述了微波技术在催化剂的合成、活性组分的负载等方面的研究应用,重点探讨了在分子筛催化剂的合成中微波技术所表现出的优越性,对微波合成催化剂的作用机理及影响因素作了评述,并展望了微波技术在催化领域的发展前景。     

微波辐射下α-溴代,α-丁二酰亚胺基β-内酰胺衍生物的合成

自从1986年Gedye等将微波作用于酯化、水解、氧化和亲核取代反应以及Giguere等研究了微波对蒽与马来酸二甲酯的Diels-Alder环加成以来,微波已成功的应用于多种有机反应,展示出广泛的应用前景[1].本课题组在以前工作的基础上[2],在微波作用下合成了5个新的1,5-苯并硫氮杂卓-α溴代-β-内酰胺衍生物,用此方法还合成了用常规方法已经合成的5个1,5-苯并硫氮杂卓-β-内酰胺衍生物.同时研究了溶剂、时间、微波功率、反应物的物质的量之比四个因素对反应的影响.反应方程式如下:     

微波合成SrTiO~3的反应机理

研究了微波合成SrTiO~3的合成过程,XRD及电子探针的结果表明这一反应过程是由扩散控制,微波场的存在使扩散过程明显增强,存在有Sr和Ti元素的相互扩散,与常规合成有较大不同。从微波合成和常规合成反应产物的组成及显微结构等方面说明微波合成与常规合成具有不同的反应机理,微波合成在反应过程中没有出现其他的中间相,反应动力学计算表明反应过程的动力学符合Carter方程,反应的活化能为129kJ/mol,约为常规合成的1/2～1/3。     

离子液体中卤代哒嗪氟代新方法的研究

在离子液体和氟化钾反应体系中，研究了卤代哒嗪化合物的氟代反应，讨论了微波辐射条件下由卤代哒嗪化合物合成氟代哒嗪化合物的方法。用离子液体作为反应介质替代了传统的分子溶剂，提高了产物收率，简化了操作。用微波反应不仅获得了较好的收率，也缩短了反应时间。利用离子液体和微波辐射条件进行氟代反应是一种绿色化学方法。     

利用微波辐射制备2-萘甲醚的合成实验

利用微波辐射的方法合成 2 萘甲醚 ,对微波辐射功率、微波辐射时间、催化剂的用量、反应物的配比对反应产率的影响进行讨论 ,该方法与传统合成方法相比具有反应时间短 ,反应条件温和 ,简单易行 ,无污染的特点     

微波干法催化芳香醛与绕丹宁及N-苯基绕丹宁的缩合反应

利用微波辐射和固体碱性载体试剂催化绕丹宁及N-苯基绕丹宁和芳香醛的缩合反应合成了14个绕丹宁衍生物并研究了影响反应的因素。     

微波-炭还原法处理一氧化氮的研究

报道了一种不需要催化剂而直接采用微波-炭还原技术处理-氧化氮(NO)的新方法.讨论了气体流量、反应温度、微波功率和施加微波时间对活性炭与一氧化氮发生还原反应的影响.比较了连续施加微波和间歇式施加微波方式下一氧化氮与活性炭发生化学反应转化为无公害的氮气(N₂)和二氧化碳(CO₂)的效率.研究结果表明,微波功率和反应器的类型及升温速率对一氧化氮与活性炭反应效率的影响较大.在连续施加微波时,一氧化氮与活性炭反应率可达98％以上.此外,还对一氧化氮与活性炭反应后的产物进行了表征.     

Investigating the existence of nonthermal/specific microwave effects using silicon carbide heating elements as power modulators

The use of passive heating elements made out of chemically inert sintered silicon carbide (SiC) allows microwave transparent or poorly absorbing reaction mixtures to be heated under microwave conditions. The cylindrical heating inserts efficiently absorb microwave energy and subsequently transfer the generated thermal energy via conduction phenomena to the reaction mixture. In the case of low to medium microwave absorbing reaction mixtures, the addition of SiC heating elements results in significant reductions (30-70%) in the required microwave power as compared to experiments performed without heating element at the same temperature. The method has been used to probe the influence of microwave power (electromagnetic field strength) on chemical reactions. Six diverse types of chemical transformations were performed in the presence or absence of a SiC heating element at the same reaction temperature but at different microwave power levels. In all six cases, the measured conversions/yields were similar regardless of whether a heating element was used or not. The applied microwave power had no influence on the reaction rate, and only the attained temperature governed the outcome of a specific chemical process under microwave conditions.     

Nonthermal microwave effects revisited: on the importance of internal temperature monitoring and agitation in microwave chemistry

The concept of nonthermal microwave effects has received considerable attention in recent years and is the subject of intense debate in the scientific community. Nonthermal microwave effects have been postulated to result from a direct stabilizing interaction of the electric field with specific (polar) molecules in the reaction medium that is not related to a macroscopic temperature effect. In order to probe the existence of nonthermal microwave effects, four synthetic transformations (Diels-Alder cycloaddition, alkylation of triphenylphosphine and 1,2,4-triazole, direct amide bond formation) were reevaluated under both microwave dielectric heating and conventional thermal heating. In all four cases, previous studies have claimed the existence of nonthermal microwave effects in these reactions. Experimentally, significant differences in conversion and/or product distribution comparing the conventionally and microwave-heated experiments performed at the same measured reaction temperature were found. The current reevaluation of these reactions was performed in a dedicated reactor setup that allowed accurate internal reaction temperature measurements using a multiple fiber-optic probe system. Using this technology, the importance of efficient stirring and internal temperature measurement in microwave-heated reactions was made evident. Inefficient agitation leads to temperature gradients within the reaction mixture due to field inhomogeneities in the microwave cavity. Using external infrared temperature sensors in some cases results in significant inaccuracies in the temperature measurement. Applying the fiber-optic probe temperature monitoring device, a critical reevaluation of all four reactions has provided no evidence for the existence of nonthermal microwave effects. Ensuring efficient agitation of the reaction mixture via magnetic stirring, no significant differences in terms of conversion and selectivity between experiments performed under microwave or oil bath conditions at the same internally measured reaction temperatures were experienced. The observed effects were purely thermal and not related to the microwave field.     

Microwave-assisted asymmetric organocatalysis. A probe for nonthermal microwave effects and the concept of simultaneous cooling

A series of five known asymmetric organocatalytic reactions was re-evaluated at elevated temperatures applying both microwave dielectric heating and conventional thermal heating in order to probe the existence of specific or nonthermal microwave effects. All transformations were conducted in a dedicated reactor setup that allowed accurate internal reaction temperature measurements using fiber-optic probes. In addition, the concept of simultaneous external cooling while irradiating with microwave power was also applied in all of the studied cases. This method allows a higher level of microwave power to be administered to the reaction mixture and, therefore, enhances any potential microwave effects while continuously removing heat. For all of the five studied (S)-proline-catalyzed asymmetric Mannich- and aldol-type reactions, the observed rate enhancements were a consequence of the increased temperatures attained by microwave dielectric heating and were not related to the presence of the microwave field. In all cases, in contrast to previous literature reports, the results obtained either with microwave irradiation or with microwave irradiation with simultaneous cooling could be reproduced by conventional heating at the same reaction temperature and time in an oil bath. No evidence for specific or nonthermal microwave effects was obtained.     

微波固相法合成层状磷锑酸钾化合物

应用微波合成技术, 以石墨或三氧化二铁为加热介质, 合成了两种新的层状磷锑酸钾: KSbP2O8, K3Sb3P2O14。与传统固相反应相比较(典型合成条件为:950~1000℃下、24h), 微波法可在微波辐射下(2.45 GHz), 仅在40~90分钟内使反应完成。在详细研究相转变的同时, 对微波在固相合成中的作用进行了初步的讨论。     

Microwave mediated facile one-pot synthesis of polyarylpyrroles from but-2-ene- and but-2-yne-1,4-diones

Several pyrrole derivates with multiple aryl substituents were prepared conveniently in a one pot-reaction from but-2-ene-1,4-diones and but-2-yne-1,4-diones via hydrogenation of the carbon-carbon double bond/triple bond followed by amination-cyclization. The reaction could be performed with ammonium formate or alkyl/arylammonium formates under Pd/C in polyethylene glycol-200 (PEG-200) under microwave irradiation. Using this procedure, different aryl-substituted pyrroles were prepared. Furthermore, studies on microwave vs thermal conditions indicate faster heating under microwave conditions was responsible for rate enhancement.     

Microwave-assisted rapid decomposition of persulfate

Microwave irradiation has been a promising alternative to conduct several chemical reactions. In this work the microwave effects in potassium persulfate decomposition rate, under controlled conditions of temperature and microwave power, were evaluated. Higher decomposition rate constants were obtained in microwave irradiated reactions in comparison with conventional heated ones. To study the effect of high power microwave irradiation, a pulsed irradiation strategy was developed, in which the samples were repeatedly heated within short intervals of time at high power levels (500 or 1400 W). A great decomposition percentage was achieved in shorter irradiation times, showing the kinetic advantages of microwave-assisted reactions. However, it was found no differences in the reaction yields, even when high power levels were involved, proving that microwave enhancements may arise only from the ability to quickly provide a large amount of energy to the reaction medium.     

Microwave-assisted photo-Fenton decomposition of chlorfenvinphos and cypermethrin in residual water

The coupling of microwave radiation with photo-Fenton reaction for wastewater treatment was evaluated. This strategy was performed in a focused microwave digestion oven with open vessels. Ultraviolet radiation was obtained from microwave lamps (MWL) activated by microwave radiation. The operational conditions were established considering the extent of degradation of chlorfenviphos and cypermethrin used for bovine ticks (Boophilus michoplus) control. The results were based on residual carbon content, always comparing the procedures in the presence or absence of UV radiation. The combination of MWL and Fenton reaction degraded pesticide residues efficiently (>98%) in about 4 min.     

Enantioselective analysis of bambuterol in human plasma using microwave‐assisted chiral derivatization coupled with ultra high performance liquid chromatography and tandem mass spectrometry

In this study, an enantioselective analytical method based on microwave‐assisted chiral derivatization coupled with ultra high performance liquid chromatography and tandem mass spectrometry was developed for the determination of bambuterol enantiomers in human plasma. The chiral derivatization reaction was greatly accelerated by microwave irradiation. Under the optimized conditions, both the derivatization time and separation time on column was only 3 min, and the lower limit of quantification was 2.5 pg/mL. The recoveries were in the range of 90.1–93.0% without significant matrix effect. Compared with the conventional heating chiral derivatization, microwave‐assisted chiral derivatization obtained higher chiral derivatization yields with much shorter time due to the effect of microwave irradiation. Furthermore, the racemization during the derivatization reaction was systematically investigated. The results showed the concentration of acetic acid and the reaction time had significant effects on the racemization, which could be well controlled during microwave‐assisted chiral derivatization for the short reaction time. Finally, this novel approach was demonstrated by determining bambuterol in human plasma of a clinical pharmacokinetic study in eight healthy volunteers. On the basis of the results, microwave‐assisted chiral derivatization coupled with ultra high performance liquid chromatography and tandem mass spectrometry as a simple and effective enantioselective analysis technique for the determination of chiral drugs in complex biological samples showed great promise.