亚纳米级的Pd团簇的简易合成:Pd/PEG-PNIPAM复合物及其Suzuki反应中的极高催化性能（英文）

由于纳米材料的小尺寸效应,在异相催化剂中,超小的催化剂颗粒往往具有很好的催化性能,多种多样的合成稳定的小纳米颗粒的方法如百花齐放地报道出来.在这些合成方法中,为了防止小颗粒的长大,往往需要稳定剂,常用的稳定剂如功能性纳米材料,树枝状分子等.但是,由于其稳定性较差,制备超小的纳米颗粒往往非常困难,表面吸附的稳定剂也会影响其催化活性.Suzuki反应在现代精细化工合成中具有非常重要的地位.合成容易回收分离的且足以催化氯苯的异相Pd催化剂,将是一个重大的突破.我们使用单电子转移活性自由基聚合(SET-LRP)方法,合成了夹心型的PEG-PNIPEM聚合物,PNIPAM聚合在PEG-1的两端,两端都连接了25个NIPAM分子.通过氢核磁共振NMR),凝胶渗透色谱(GPC)和傅里叶变化红外光谱(FTIR),我们证明了PNIPAM已经成功地接枝在PEG的两端,PEG-PNIPAM的数均分子量Mn,GPC为7841.通过简单的负载流程,我们将Pd纳米颗粒成功的地负载在PEG-PNIPAM共聚物上,得到Pd/PEG-PNIPAM催化剂,Pd的负载量为4.4 wt%.在透射照片中,PEG-PNIPAM看起来像一个薄薄的片层.Pd的团簇颗粒很小,最大约2 nm.我们测量了制得的催化剂Pd/PEG-PNIPAM水溶液随着温度变化的光透过率曲线,最后确定该材料的LCST为41℃.我们认为在温度高于LCST进行反应时,催化剂的载体由亲水变成亲油,这样亲油的反应物分子将容易向催化剂载体扩散并富集.催化剂会形成一个亲油的微环境富集反应物,并形成反应微环境将大大提高催化速率.该催化剂在Suzuki反应中表现出了极好的催化能力.使用该催化剂催化Suzuki反应,我们发现苯硼酸和碘苯在80℃反应时10 s内即可完全转化,TOF为4.3×10~4 h~(-1).对于异相Pd催化剂而言,达到这个TOF是非常难得的,可与活性很高的均相催化剂比拟.室温下催化速率明显减慢,但也仍在1 min内转化完全,TOF为7.2×l0~3 h~(-1).当加大反应物的量,反应物/催化剂的比从120增加到1600,反应在3 min内达到100%转化,TOF为3.2×l0~4 h~(-1).即使使用苯硼酸和氯苯进行反应,也在5 min内达到了65%的转化.异相Pd催化剂催化氯苯的Suzuki反应是很难进行的,表明该纳米材料具有极佳的催化活性.然而,在催化苯硼酸与碘苯的连续3次反应中,催化剂的活性明显降低,直至失活.使用后的催化剂颗粒长大至几百纳米,许多小颗粒被包裹于其中.Pd颗粒有所长大,PEG-PNIPAM相互缠绕发生团聚,这也就是催化剂失活的原因.由于Pd/PEG-PNIPAM复合物可以通过其温度响应性回收,我们认为其在高效催化方面具有很好的应用前景.     

双子季铵盐稳定的纳米钯催化Suzuki反应的研究

双子座季铵盐能够稳定现场产生的纳米钯粒子,该纳米钯粒子能有效地催化一系列芳基硼酸和芳基卤代烃发生Suzuki偶联反应.双子座季铵盐稳定的纳米钯粒子能够在空气中稳定存在,透射电镜(TEM)分析纳米钯粒子呈圆球形,粒径分布在5～25 nm.该方法具有反应条件温和、反应时间短、后处理简单方便等优点.     

Pd单原子/团簇高效催化铃木偶联反应

铃木偶联反应是合成聚烯烃、苯乙烯和联苯衍生物等功能性有机化合物的有力工具,广泛应用于精细化工、制药和生化工业领域.钯(Pd)基催化剂是目前性能最好的铃木偶联反应催化剂,但钯的低丰度和高成本限制了其大规模应用.因此,提高Pd原子的利用效率,降低Pd用量至关重要.减小金属纳米粒子的尺寸,使其成为小团簇甚至孤立的金属原子是实...     

Suzuki反应中催化体系的研究进展

随着过渡金属催化的交叉偶联反应的出现,有机合成化学在20世纪的最后25年得到了快速的发展,并且这些反应的重要性被普遍认可.其中,Suzuki偶联反应因其多功能性、兼容性和对包括材料科学和药物合成在内的多种学科的关键贡献,而占据了更加特殊的地位.尽管到2010年为止Suzuki反应已取得重大进展,但随着可持续和绿色化学发展的需求,Suzuki反应的催化体系仍待进一步优化提高.这里概述的催化剂为C-C键的构建提供了方便和绿色的合成途径.在这篇综述中,我们总结了科研工作者对于Suzuki反应在改进催化剂制备策略、优化催化反应条件、提高催化剂重复利用性能和降低催化剂成本方面做的一系列研究.     

纳米钯/[BDABCO]Br/H2O体系催化的Suzuki反应

采用水为反应介质,在溴化1-丁基-4-氮杂-1-氮鎓双环[2.2.2]辛烷([BDABCO]Br)存在下,纳米钯能有效地催化一系列卤代芳烃与芳基硼酸发生Suzuki交叉偶联反应,以良好产率生成联苯类产物。该催化体系nano-Pd/[BDABCO]Br/H2O对底物官能团无影响,产物可通过简单萃取分离,产率优良,对环境友好。     

四乙烯五胺功能化纤维素负载纳米钯催化剂的制备及其对Suzuki反应催化性能的研究

利用四乙烯五胺对环氧化纤维素进行功能化改性,并以其为载体在95％乙醇溶液中现场还原氯化钯制备出四乙烯五胺功能化纤维素负载的纳米钯催化剂.利用IR,XRD,SEM,TEM等分析方法对其进行了表征并用于催化Suzuki交叉偶联反应.实验表明,该催化剂在温和条件下能有效催化卤代芳烃与芳基硼酸的Suzuki交叉偶联反应,该催化剂经回收重复利用5次后,仍具有较高的催化活性.     

乙二胺功能化纤维素负载纳米钯催化Suzuki反应的研究

以氯化纤维素为原料, 通过与乙二胺的胺化反应制得乙二胺功能化纤维素(Cell-EDA), 然后再将胺化纤维素在氯化钯乙醇溶液中反应可以方便制备得到乙二胺功能化纤维素负载的纳米钯催化剂(Cell-EDA-Pd0). 用SEM, TEM等分析方法对所制备的催化剂进行了表征; TEM分析表明乙二胺功能化纤维素负载的纳米钯呈球形, 粒径在10～20 nm左右. 实验结果表明, Cell-EDA-Pd0催化剂对空气稳定, 无需在惰性气体的保护下就能有效地催化芳基硼酸与卤代芳烃的Suzuki交叉偶联反应, 催化剂易回和收重复使用, 催化剂重复使用6次催化活性没有明显降低.     

碳载高分散钯纳米粒子的制备及催化Suzuki反应

利用三聚氰胺甲醛预聚物中N原子与Pd²⁺的相互作用,将Pd²⁺化学锚定在预聚物中;并以二氧化硅水凝胶为造孔剂、2,4-二氨基苯磺酸为预聚物缩合促进剂,在水溶液中制备出锚定了Pd²⁺的胶体纳米球;再经摩尔分数5%氢气焙烧、HF腐蚀,得到Pd质量分数为1.37%、平均粒径为(2.4±0.87) nm的碳载高分散Pd纳米粒子催化剂Pd@C。 将其应用于Suzuki反应,在加入Pd与碘苯物质的量比为1:100的催化剂时,反应5 min收率为99.3%,且经8次循环后活性未降低,表现出良好的催化效果和重复使用性。     

高核Ag/S纳米团簇合成的研究进展

硫醇配体保护的高核银纳米团簇具有丰富的结构和性能, 在光致发光、 生物传感、 纳米材料等方面具有广阔的应用前景. 然而, 精确控制高核Ag/S纳米团簇的尺寸和结构面临着巨大的挑战, 构建高核Ag/S纳米团簇的可行策略也一直是人们关注的焦点. 近年来, 随着合成方法和表征技术的不断发展, 高核Ag/S纳米团簇的合成和性能研究方面均取得了显著的成就. 本文总结了含20个或以上Ag原子的Ag/S纳米团簇的合成方法(直接还原法、 阴离子模板法及配体交换法), 对部分高核Ag/S纳米团簇的结构进行了探讨, 并展望了未来研究的趋势.     

嵌入Y型沸石中Pd簇的合成及其催化性能

以［Ｐｄ（ＮＨ３）４］（ＮＯ３）２·Ｈ２Ｏ作为离子交换前驱物，应用微波交换－氢还原法合成了嵌入Ｙ型沸石中的Ｐｄ簇合物。ＸＲＤ和ＰＸＳ测试结果表明，在合成过程中，焙烧阶段的温度是影响Ｐｄ原子进入沸石体相形成Ｐｄ簇的主要因素。在焙烧温度２４０℃和还原温度２１０℃的制备条件下，Ｐｄ含量高达６．１３％（质量分数）也能进入Ｙ型沸石体相形成Ｐｄ簇。在相同条件下制得Ｐｄ含量仅为０．４１０％（质量分数）的样品，在     

Synthesis of Xenbucin using Suzuki reaction catalyzed by Pd/C in water

Xenbucin 1, an analgesic drug, was synthesized in 4 steps using two different routes. The biaryl fragment could successfully be produced via a Pd/C catalysed Suzuki coupling in water using sodium tetraphenylborate as a phenylation reagent. Overall yields of the routes were 36% and 59%, respectively.      

纯水中有氧条件下Pd/C催化的无配体Suzuki反应简

报道一种在纯水中Pd/C催化的高效Suzuki反应体系,该体系无需除氧,且无外加配体和添加剂,底物普适性广泛,含有亲水或疏水基团的溴代芳烃都能被高效活化. 此外,对部分杂环芳烃与芳基硼酸的偶联反应也有较好的催化效果. 该催化剂可高效循环使用三次,且性能无明显下降.     

New route to synthesis of PVP‐stabilized palladium(0) nanoclusters and their enhanced catalytic activity in Heck and Suzuki cross‐coupling reactions

Herein we report a new method for the synthesis and characterization of PVP‐stabilized palladium(0) nanoclusters and their enhanced catalytic activity in Suzuki coupling and Heck reactions of aryl bromides with phenylboronic acid and styrene, respectively, under mild conditions. The PVP‐stabilized palladium(0) nanoclusters with a particle size of 4.5 ± 1.1 nm were prepared using a new method: refluxing a mixture of potassium tetrachloropalladate(II) and PVP in methanol at 80 °C for 1 h followed by reduction with sodium borohydride. Palladium(0) nanoclusters prepared in this way were stable in solution for weeks, could be isolated as solid materials and were characterized by TEM, XPS, UV–vis, and XRD techniques. The PVP‐stabilized palladium(0) nanoclusters were active catalysts in Heck and Suzuki coupling reactions of arylbromides with styrene and phenylboronic acid affording stilbenes and biphenyls, respectively, in high yield. Recycling experiments showed that PVP‐stabilized palladium(0) nanoclusters could be used five times with essentially no loss in activity in the Heck and Suzuki coupling reactions. Copyright © 2009 John Wiley & Sons, Ltd.     

Carbon nanotubes-supported palladium nanoparticles for the Suzuki reaction in supercritical carbon dioxide: A facile method for the synthesis of tetrasubstituted olefins

A facile and efficient method for the synthesis of tetrasubstituted olefins in supercritical carbon dioxide was developed by using carbon nanotubes-supported palladium nanoparticles (Pd/CNTs) as the catalyst. Compared with common Pd/C, Pd/CNTs could more effectively catalyze the reaction of dibromo-substituted olefins with boronic acids, affording the corresponding tetrasubstituted olefins with moderate to good yields. This environmentally benign route with an easy-to-handle catalyst provides an appealing alternative to the currently available methods.     

Synthesis,characterization and catalytic activity of new aminomethyldiphosphine–Pd(II) complexes for Suzuki cross‐coupling reaction

A new range of CF₃‐substituted aminomethyldiphosphine (P―C―N) ligands ((C₆H₅)₂PCH₂)₂NR (R = ―C₆H₄(2‐CF₃) ( 1 ), ―C₆H₄(3‐CF₃) ( 1b ) has been synthesized from 2‐(trifluoromethyl)aniline and 3‐(trifluoromethyl)aniline with diphenylphosphine. The aminomethyldiphosphine ligands were reacted with Pd(cod)Cl₂ to give corresponding metal complexes, PdLCl₂ ( 2a , 2b ). The aminomethyldiphosphine–palladium compounds were characterized by utilizing several methods including NMR (¹H, ¹³C, ³¹P) and elemental analysis. These compounds were used as catalysts in Suzuki cross‐coupling reaction of aryl chlorides and bromides. The effect of base was also investigated in this current project. CF₃‐substituted aminomethyldiphosphine–palladium complexes were found to be efficient catalysts in Suzuki cross‐coupling reaction of activated and deactivated aryl boronic acids. Copyright © 2013 John Wiley & Sons, Ltd.     

Shape-dependent catalytic activity of copper oxide-supported Pd(0) nanoparticles for Suzuki and cyanation reactions

Palladium nanoparticles supported on different shapes of nanocrystalline CuO are prepared by the treatment of Cu(NO₃)₂ and Pd(OAc)₂ in polyethylene glycol (PEG-6000). The shapes of the CuO/Pd composite are dependent on the amount of PEG used. Suzuki coupling was catalyzed efficiently by the oval-shaped material, whereas the rod shape facilitates the cyanation reaction. The CuO/Pd catalyst is recovered and reused for subsequent Suzuki reactions; however, cyanation poisons the catalyst for further use. Both these reactions are very clean and high yielding.     

Efficient synthesis of isoflavone analogues via a Suzuki coupling reaction

Analogues of 3-aryl-8-isobutyl-5,6,7-trihydroxy-2-methyl-4H-chromen-4-one were synthesized with high yields via the Suzuki coupling reaction of 3-iodo-8-isobutyl-5,6,7-trimethoxy-2-methyl-4H-chromen-4-one with different aryl boronic acids.     

Efficient synthesis of substituted biaryl anilines and biaryl phenols via a Suzuki cross-coupling reaction

An efficient synthesis of biaryl building blocks with multiple point diversities via a Suzuki cross-coupling reaction using a commercially available preformed Pd catalyst 1 was reported. Substituted biaryl anilines and phenols were obtained in one step from commercially available aryl halides.     

Room-temperature oxidative Suzuki coupling reaction of 1,2,3-triazole N-oxides

This study develops a new efficient pathway for synthesis of 2,4-disubstituted 1,2,3-triazoles through regioselective direct arylation between 2-aryl-1,2,3-triazole N-oxides and Ar-B(OH)₂. The reaction proceeds smoothly at room temperature and exhibits good yield and high C5 position selectivity. The possible pathway of oxidative Suzuki coupling is also discussed. This simple methodology can be used to construct 2,4-disubstituted 1,2,3-triazole moiety.     

Green synthesis of fluorinated biaryl derivatives via thermoregulated ligand/palladium-catalyzed Suzuki reaction

Fluorinated compounds have attracted considerable attention in pharmaceuticals, agrochemicals and material science due to their unique physical properties. This paper reports an efficient and environmentally benign protocol for the Suzuki reaction of aryl halides with fluorinated arylboronic acids over a thermoregulated ligand/palladium catalyst using water as sole medium, affording a variety of fluorinated biaryls, including fluorinated liquid crystals, in excellent yields. The catalyst could be recycled four times with high activity. The active catalyst was proved to be a palladium/ligand complex via a mercury-poisoning test.