【作者】 陈秋；

【导师】 刘双喜；

【作者基本信息】 南开大学 ， 材料物理与化学， 2012， 博士

【摘要】 近几年来，不对称有机催化由于其原子经济性高的特点受到广泛关注，已经成为不对称催化最为活跃的领域之一。金鸡纳生物碱及其衍生物作为一类高效的有机小分子催化剂，因其分子结构含有多个手性中心且易于修饰，在不对称有机催化领域受到了广大化学工作者的青睐，已经被广泛用于催化不对称Michael加成、不对称Aldol等反应。然而，金鸡纳均相催化剂往往存在用量高、不易回收以及产物分离困难等缺点，很大程度上制约了其在工业上的应用。均相催化剂的固载化有望克服上述缺点，因而备受研究者的重视。目前固载化金鸡纳催化剂的应用范围主要集中在不对称双羟基化和不对称烷基化反应，在目前均相催化剂研究较为活跃的不对称Michael加成以及Aldol反应领域，相关的研究却较少。无机载体因其高的机械强度、较好的热稳定性等特点，成为固载均相催化剂的优良载体。为此，本文分别采用介孔氧化硅SBA-15和杂多酸作为载体实现了天然金鸡纳生物碱与金鸡纳手性胺的固载化，并将所得的催化剂用于催化不对称Michael加成与Aldol反应。考察了不同固载方法——后嫁接法与共缩聚法，以及不同载体——片状短孔道SBA-15与纤维状常规SBA-15分别对催化剂催化不对称Michael加成反应的影响。同时也研究了共价固载法与静电固载法对催化剂催化不对称Aldol反应的影响。本文首先采用简单的后嫁接法实现了天然金鸡纳生物碱奎宁在介孔材料SBA-15表面的成功固载。XRD、FT-IR、DR UV-Vis、TG-DTG、氮气吸附以及元素分析结果表明奎宁成功地被引入到了SBA-15表面，并且所得的催化剂依然保持了较好介孔结构以及规整的介孔孔道。以查耳酮类化合物的不对称Michael加成反应为模型反应，研究了不同溶剂对催化性能的影响，同时也考察了催化剂的循环使用性能。除了甲氧基查耳酮之外，该催化体系获得了中等水平的收率，但产物ee值相对较低。共缩聚法制备的催化剂相比后嫁接法，活性组分在载体表面分布得更为均匀，手性诱导作用可能进一步增强，从而促进对映选择性的提高。本文采用共缩聚法合成了巯丙基硅烷修饰的有机-无机杂化介孔SBA-15，并通过自由基加成反应首次引入了奎宁催化剂。XRD、FT-IR、DR UV-Vis、TG-DTG、氮气吸附以及元素分析结果表明，奎宁被成功地固载到了介孔材料的表面，在有机硅烷投料量不超过20mol%(占总硅烷物质的量分数)时，所制备的非均相催化剂依然保持了较好介孔结构以及相对规整的介孔孔道。以查耳酮类化合物的不对称Michael加成反应为模型反应，考察了不同合成条件对催化性能的影响，发现最佳的有机硅烷投料量为20mol％，最佳晶化温度为100℃，最佳晶化时间为24h。相比于后嫁接法，共缩聚法制备的催化剂对映选择性明显提高，但反应收率依然受到微米级长孔道的限制，无明显提高。短孔道的SBA-15与传统的SBA-15相比，更短的孔道有利于反应的传质，促进反应的活性的提高。本文首次采用共缩聚方法合成了巯丙基修饰的、同时具有片状形貌的短孔道SBA-15，并进一步将不同结构的金鸡纳生物碱固载到该材料的介孔孔道中。XRD、FT-IR、DR UV-Vis、TG-DTG、SEM、TEM、氮气吸附以及元素分析结果证明金鸡纳生物碱的成功固载，并且所有非均相催化剂都保持了较好的介孔结构。SEM和TEM证实了催化剂具有片状形貌，孔道长度约为280~480nm。以查耳酮类化合物的不对称Michael加成反应为模型反应，考察了有机硅烷投料量和金鸡纳生物碱结构对非均相催化剂的催化性能的影响，结果发现最佳的有机硅烷投料量为10mol%；各种金鸡纳结构的非均相催化剂中，奎宁催化剂表现出了最优的催化性能。与常规催化剂相比，短孔道催化剂的催化活性得到了大幅度的提高，且对映选择性也略有提高。元素分析和FT-IR表明催化剂强吸附原料丙二腈是其循环性能降低的主要原因。静电固载是手性催化剂固载化的重要手段之一。本文首次以杂多酸为载体，通过静电相互作用，实现了金鸡纳手性胺催化剂的非均相化。NMR、FT-IR以及元素分析结果表明金鸡纳手性胺被成功地固载在杂多酸上，以芳香醛的不对称Aldol反应为模型反应，考察了固载方式、杂多酸与溶剂类型、以及底物结构对催化反应的影响。结果发现，因共价固载的方式破坏了金鸡纳C-10位的双键结构，导致共价键联的催化剂无任何对映选择性；酸性最强的磷钨酸为最佳载体；丙酮最有利于非均相催化体系；底物空间因素对催化反应结果有较大的影响。催化剂的质量损失是循环反应结果降低的主要原因。更多还原

【Abstract】 Recently, asymmetric organocatalysis, one of the most active researchfields of asymmetric catalysis, has been received much attention due toits high atom economy. Cinchona alkaloids and their derivatives as onekind of efficient organocatalysts have fascinated researchers. Owing totheir easily modified structure and multiple chiral centres, cinchonaorganocatalysts are widely used in asymmetric Michael addition andasymmetric Aldol reactions. However，the high dosage of the catalyst anddifficulties in separation and recovery restrict their use in industry. Theseproblems resulting from homogeneous process can be overcome by theimmobilization of cinchona catalysts on various supports, which havecalled great attentions from researchers. While heterogeneous cinchonacatalysis in asymmetric dihydroxylation and asymmetric alkylation is stilla major topic at present， the study for heterogeneous catalyst in asymmetric Michael addition and asymmetric Aldol reactions remainsrare.Inorganic materials are considered as ideal supports for chiralcatalysts，because of their high mechanical strength and thermal stability.In this paper, nature cinchona alkaloid and cinchona-derived chiral aminewere immobilized on mesoporous silica and polyoxometalates forasymmetric Michael addition and asymmetric Aldol reactions. Theeffects of different synthetic methods—post-synthesis grafting anddirect co-condensation method, and different supports—SBA-15withplatelet and fiber morphology on the catalytic performance ofheterogeneous catalysts were evaluated in the asymmetric Michaeladdition. The influence of different immobilization strategies, includingcovalent and electrostatic immobilization, on the catalytic performance inthe asymmetric Aldol reactions was also investigated.Quinine was firstly supported on the mesoporous silica SBA-15via post-synthesis grafting. The heterogeneous catalyst was characterized byXRD, FT-IR, DR UV-Vis, TG-DTG, N2sorption, elemental analysis andit was showed that quinine was successfully immobilized on SBA-15andthe prepared catalysts still maintained characteristic mesoporous structureand ordered mesochannels. The effect of different solvents on thecatalytic performance of heterogeneous catalyst was evaluated in theconjugate addition of malononitrile to chalcones. Catalyst recyclingstudies were also carried out. Except4-methoxychalcone, moderate yieldand unsatisfactory ee value were obtained by the heterogeneous catalyst.Compared with post-synthesis grafting, the co-condensation methodoften results in the heterogeneous catalyst with more homogeneouslydistributed active sites on the surface, which might enhance the chiralinduction and offer more suitable reaction microenvironment for thereaction. Herein, mercaptopropyl functionalized mesoporous SBA-15was prepared by co-condensation method and then quinine was incorporated onto the support surface by the free radical addition reaction.The results of XRD, FT-IR, DR UV-Vis, TG-DTG, N2sorption andelemental analysis disclose that quinine was successfully immobilized onthe surface of support. Furthermore, when the dosage of organosilanewas less than20mol%(the molar percentage of silicon atoms in theinitial mixture as organosilane), the heterogeneous catalyst couldmaintain the characteristic mesoporous structure and orderedmesochannels. The effects of different synthesis conditions on catalyticperformance were investigated and the optimal conditions were asfollows: the dosage of organosilane should be20mol%, thecrystallization temperature should be100℃and time should be24h.The heterogeneous catalyst was tested in the conjugate addition ofmalononitrile to chalcones. It was found that the enantioselectivity wassignificantly improved by the catalyst prepared via the co-condensationmethod. However, the yield was basically unchanged due to the long mesochannels in micrometer scale.Mesoporous SBA-15with short mesochannels is proved to be morefavorable for mass transfer than the conventional SBA-15, which alwaysleads to enhanced catalytic activity. In our study, mercaptopropylfunctionalized mesoporous SBA-15with platelet morphology and shortmesochannels was synthesized by co-condensation method and cinchonaalkaloids were then immobilized on such organic-inorganic mesoporoussilica materials. The heterogeneous catalysts were characterized by XRD,FT-IR, DR UV-Vis, TG-DTG, SEM, TEM, N2sorption and elementalanalysis. The characterization results indicated that cinchona alkaloidswere successfully incorporated onto the surfaces and thoese catalystsremain mesoporous structure. SEM and TEM showed that theheterogeneous catalysts have hexagonal platelet morphology and the porelength of the catalysts was about280nm~480nm. The influences of theorganosilane dosage and the structure of cinchona alkaloids on the catalytic performance of heterogeneous cinchona catalyst were alsostudied. It was found that the best dosage of organosilane was10mol%and the heterogeneous quinine catalyst was superior to other cinchonacatalysts. Not only enhanced catalytic activity but also improvedenantioselectivity were obtained by the heterogeneous catalyst with shortmesochannels. Element analysis and FT-IR confirmed that the active sitesbeing covered by the reactant (malononitrile) might be the main reasonfor the loss of activity and enantioselectivity during the recycle process.Electrostatic immobilization is one of the most importantimmobilzation strategies. In our work, cinchona-derived chiral amine wasfirstly supported on polyoxometalate acid by electrostatic interaction. Thecatalyst was characterized by NMR, FT-IR and elemental analysis. Theresults indicated that cinchona-derived chiral amine was successfullyimmobilized on the polyoxometalate acid. The influences of differentimmobilzation strategies, heteropoly acids, solvent and substrates on the catalytic performance of the heterogeneous catalysts were evaluated inthe asymmetric Aldol reaction of aromatic aldehydes. It was found thatcinchona-derived chiral amine covalently immobilized on SBA-15provided racemic product and C-10double bond being destroyed mightbe the main reason. Other influential factors on the catalytic performancewere also studied and the optimal conditions were as follows: theappropriate polyoxometalate acid was phosphotungstic acid whichpossesses the highest acid strength, and the best solvent was acetone. Theexperiments also showed that the space factor from substrate couldeffectively affect the catalytic result. The recycle study indicated that themain reason for the decrease of the catalytic activity was the mass loss ofcatalyst.更多还原