【作者】 刘诗咏；

【导师】 姜玄珍； 许宜铭；

【作者基本信息】 浙江大学 ， 化学， 2008， 博士

【摘要】 钯催化的芳基溴或芳基碘的Suzuki及Heck偶联反应是现代有机合成中重要的反应。这些偶联反应在材料、天然产物及生物活性物质的制备中有着极其重要的地位。发展无膦配体的可循环使用的非均相催化剂以取代昂贵的对空气敏感的碱性膦配体有重要的实际应用价值。本论文发展了四种新的无配体型Heck及Suzuki反应催化剂。水滑石（LDHs）是一种重要的无机层状材料,其在催化剂、催化剂前驱体及载体、吸附、纳米复合材料以及药物控释等领域有广泛的使用价值。本文利用离子交换的方法将十二烷基磺酸根（DS^-）插层进入到水滑石的层板间（即MgAl-LDH-DS）。对该十二烷基磺酸根插层的LDHs进一步以PdCl₄^2-交换即可得到DS^-和PdCl₄^2-双插层的LDHs(即PdCl₄^2-/MgAl-LDH-DS)。层间PdCl₄^2-进一步以抗坏血酸（Vc）还原即得到层间插有金属Pd⁰团簇的水滑石（即Pd⁰/MgAl-LDH-DS）。由于十二烷基磺酸根插层后在水滑石层板间形成的空间有限（2-3 nm）,在这有限空间限制了Pd⁰团簇的进一步生长。这种限域作用对于维持pd⁰的催化活性及其稳定性起到了至关重要的作用。此外,十二烷基磺酸根（DS^-）在水滑石层板间形成的微空间具有亲水亲油两性,有机反应物分子可以自由出入于该微空间,与其间的Pd⁰发生催化反应,相当于在LDHs层板间制备了一个两亲性的微反应器。试验表明,这是一种高效的Suzuki偶联反应催化剂。由于层状材料层板结构被剥离后,其内表面将充分向外界暴露,这种现象在催化及吸附领域有重要的应用价值。LDHs是由层板带正电的二价及三价羟基化物及层间带负电荷的阴离子交替叠加形成的层状结构。对这种层状结构的剥离,可以使剥离后的LDHs比表面积理论值达到1000 m²/g。水滑石的剥离研究相对滞后,实际上,水滑石之外的其它层状材料的剥离已有不少实际应用的报道。在水滑石的剥离方面,虽然从2000年的首例报道后已有不少文献报道,但绝大多数侧重于LDHs剥离的方法学上的研究,而忽略了其实际应用方面的研究。本论文首次报道了共沉淀法制备所得的甘氨酸（Gly）插层的层板含钯的三元水滑石MgPdAl-LDH([Mg_0.95Pd_{0.05Al1/3（OH）2][Gly1/3·mH2O]}在甲酰胺中的完全剥离,并将该剥离后的层板呈单分散态的MgPdAl-LDH用于催化Heck偶联反应。由于MgPdAl-LDH被剥离后其内表面全面向反应物分子开放,这些MgPdAl-LDH单一层板对众多卤代芳烃的Heck偶联反应均表现出优异的催化活性。在这些单一的MgPdAl-LDH层板中,钯位点和碱性位点处于分子水平上的混合,因此,MgPdAl-LDH层板中的碱性位点充当了碱性配体的角色。碱性位提供的富电子氛围促进了卤代芳烃对钯的氧化加成,从而完成对卤代芳烃的活化。这种先将催化元素引入到LDHs层板中再进行剥离的思想可望延伸到钯以外的其他过渡金属。本论文还发展了一种简易的磁性Fe₃O₄纳米粒子负载Pd⁰的方法。利用FeO3_O4溶胶带正电荷的特性,将负离子PdCl₄^2-通过静电作用吸附在Fe₃O₄胶体粒子表面(记为PdCl₄^2-/Fe₃O₄),以抗坏血酸（Vc）进一步还原即得到负载有金属Pd团簇的Fe₃O₄胶体粒子（记为Pd⁰/Fe₃O₄）。这种磁性载体负载的Pd催化剂对Suzuki反应表现出良好的催化活性,并且在反应后,可以简单地通过永久磁铁将催化剂从反应体系中分离出来,进行循环使用。循环试验表明,该催化剂在循环使用五次后反应活性没有明显的下降。酞菁化合物是一类被广泛研究的功能性分子。作为功能材料,酞菁的固载化（载体一般为金属氧化物半导体）对于充分实现其功能具有关键性作用。磁性Fe₃O₄纳米粒子是另一重要功能材料。酞菁与Fe₃O₄纳米粒子在性质和功能上有很好的互补性。两者的有效结合在催化、光催化以及抗癌治疗上均有潜在的应用价值。本文利用超临界乙醇干燥所得的Fe₃O₄纳米粒子的表面活性Fe原子与酞菁前驱体邻苯二腈[Ph（CN）₂]反应直接得到表面包覆有酞菁铁（FePc）单分子层的Fe₃O₄纳米粒子（记为FePc@Fe₃O₄）。这是一种全新的酞菁铁修饰氧化铁的方法,该方法有望延伸到其他金属氧化物纳米粒子（如TiO₂和Fe₂O₃）及邻苯二腈的其他衍生物。有趣的是,这种原位生成的FePc@Fe₃O₄纳米复合材料对Heck偶联反应同样表现出催化活性。该非钯体系催化的Heck反应对于Heck反应机理的探索将起到促进作用。更多还原

【Abstract】 The palladium catalyzed coupling of bromo- and iodoarenes by Heck and Suzuki reactions is a well-established methodology in modem organic synthesis.The coupling products find good applications as intermediates in the preparation of materials,natural products and bioactive compounds.It is highly desirable to develop a phosphine-free new recyclable heterogeneous catalytic system to dispense the use of expensive and air-sensitive basic phosphines for palladium catalyzed coupling reactions of haloarenes.Four types of novel ligandless Pd or non-palladium catalysts for Heck and Suzuki reactions were developed in the current dissertation.Layered double hydroxides（LDHs）,an important family of inorganic layered materials,have been found wide applications as catalysts,catalyst precursors or supports,adsorption,nanocomposite and drug delivery.Herein,surfactant （DS’）-intercalated LDHs（MgAl-LDH-DS）were prepared via ions exchange method. Further exchange of DS^- with PdCl₄^2-resulted in LDHs intercalated by both DS" and PdCl₄^2-(PdCl₄^2-/MgAl-LDH-DS).Pd⁰/MgAl-LDH-DS were further obtained via the reduction of PdCl₄^2-/MgAl-LDH-DS with Vc.The Pd⁰ clusters were intercalated between the LDHs layers;hence the growth of Pd⁰ clusters would be effectively hindered by the limited space of the inter-layers created by the pre-intercalation of DS^-.The micro-space between LDH layers created by surfactant was hydrophobic,so the organic reactants could enter freely into these micro-reactors and interact with the pre-implanted Pd⁰ cluster,resulted in effective catalysis toward Suzuki reaction.Delaminating layered materials is of tremendous practical importance in applications due to the largely enhanced accessibility of their inner surface.Layered double hydroxides are layered materials constituted by a stacking of positive hydroxylated layers[M²⁺_1-xM^3+x_x（OH）₂]^x+separated by interlayered anionic species and water molecules[A_x/n^n-·m H₂O]^x-.As a consequence of its structure,the delaminated LDH phase would reach a theoretical specific surface area of 1,000 m²/g. Actually,applications of delaminated layered materials rather than LDHs have been developed previously.However,the practical application of delaminated LDH is still in its infancy,despite that the strategies for delaminations of LDHs have been relatively well-documented and well-established since the first case of the LDH delamination by use of surfactant was reported in 2000.In the present work,A novel ligand-free catalyst,Pd（Ⅱ）-doped colloidal layered double hydroxide（LDH）,has been prepared from delamination of glycinate intercalated ternary-component MgPdAI-LDH([Mg_0.95Pd_0.05Al_1/3（OH）₂][Gly_1/3·mH₂O])in formamide.Subsequently, the catalytic performance of these mono-dispersed ultrathin nanosheets of LDH for Heck reaction was evaluated.Owing to the largely enhanced accessibility for reactant molecules resulting from the nature of high inner surface area of LDHs,these palladium-bearing nanosheets showed excellent efficiency for Heck reactions to a wide range of substrate molecules.The Pd sites and basic sites on the brucite-like nanosheets are combined at a molecular level and interact with each other closely because of the co-precipitation method employed;so the basic sites on the LDH monolayers might function as basic ligands.The electron-rich environment derived from basic sites of LDH layers would provide the requisite electron density on palladium to undergo oxidative addition of in situ formed Pd（0）with haloarene, accounting for the highly catalytic efficiency.This method of combination of catalytically active sites with LDHs might be extended to transition metals other than Pd（Ⅱ）.The present work also developed a simple way to combine Pd⁰ with Fe₃O₄ nanoparticles（NPs）,PdCl₄^2-was immobilized directly on the cationic Fe₃O₄ colloids through electrostatic interaction.Further reduction of these PdCl₄^2-/ Fe₃O₄ NPs resulted in Pd⁰/Fe₃O₄ NPs.These magnetic NPs-supported Pd⁰ clusters showed high efficiency toward Suzuki reactions.After reactions,the Pd⁰/ Fe₃O₄ NPs could be simply recycled by permanent magnet.This catalyst could be re-used for 5 times without significant loss in catalytic activity.Phthalocyanines（Pcs）are one of the most extensively studied functional materials. As functional materials,the immobilization of Pcs on some supports（e.g.,metal oxides）is essential for fully exploiting their functionalities.Both Fe₃O₄ nanoparticles （NPs）and Pcs are important functional materials,they are complementary in both properties and functions.The effective combinations of these two kinds of materials have potential application in catalysis,photo-catalysis and anticancer therapy.In the present work,SCFD-derived Fe₃O₄ nanoparticles were chose as substrate to react with phthalic nitrile（Ph（CN）₂）superficially to form FePc monolayer on the surface of Fe₃O₄ NPs.Using these two simple starting materials,Fe₃O₄ NPs chemically coated with FePc monolayer were obtained just in one step.To our best of knowledge,it is a totally new strategy to functionalize iron oxides with FePc.Also this method may be extended to other metal oxide（e.g.,TiO₂ and Fe₂O₃）nanoparticles and other phthalic nitrile derivatives.More interestingly,this in situ formed FePc@Fe₃O₄ nano-composite also exhibited catalytic activity toward Heck reaction;it is a non-palladium-catalyzed Heck reaction.This finding will lay a foundation to understand more accurately the mechanism of Heck reactions.更多还原