【作者】 谭蓉；

【导师】 银董红；

【作者基本信息】 湖南师范大学 ， 有机化学， 2009， 博士

【摘要】 手性Schiff碱过渡金属配合物,因其灵活多变的结构与优异的催化性能在不对称催化烯烃环氧化反应中备受关注。针对均相手性Schiff碱过渡金属配合物催化剂难分离以及多相手性Schiff碱过渡金属配合物催化剂活性相对较低的问题,本文采用自组装、聚合、轴向配位或共价键联的方法,设计和制备了一系列结构新颖且具有溶剂控制相转移功能的手性Schiff碱过渡金属配合物催化剂。该类催化剂的特点是可以通过调变溶剂,控制其在反应体系中的反应与分离。在非官能化烯烃不对称环氧化反应和硫醚不对称氧化反应中,催化剂在反应过程中与反应介质互溶,表现为均相催化;反应完成后,加入与催化剂不溶的萃取剂,催化剂以固体形式从反应体系中析出,实现了催化剂在反应体系中“一相催化,两相分离”。该类溶剂控制相转移催化剂既保留了均相催化剂高活性和高对映选择性的优点,又具有多相催化剂易分离和可重复使用的优点,实现了催化剂反应分离一体化。利用“自负载”策略,通过双齿桥联Schiff配体与金属锰离子之间配位自组装,合成了一种类salen Mn（Ⅲ）金属-有机自组装聚合物。用元素分析、FT-IR、NMR、UV-vis对制备的催化剂进行了结构表征。所制备的催化剂具有较大的分子量,使其在有机溶剂中具有选择溶解的特点。在非官能化烯烃的环氧化反应中,该金属-有机自组装聚合物催化剂表现出与传统salen Mn（Ⅲ）配合物催化剂相当的催化活性,通过变换溶剂,催化剂可以从反应体系中简单分离。该金属-有机自组装聚合物催化剂可有效重复使用8次以上,催化剂活性和产物选择性没有明显下降。运用Guassian 03软件,结合密度泛函理论,对类salen Mn（Ⅲ）金属-有机自组装聚合物结构进行了模拟和优化,证实了该聚合物催化剂和传统Salen Mn（Ⅲ）配合物具有相似的结构特点。利用缩聚法,通过手性环己二胺与3-叔丁基-5-氯甲基水杨醛聚合,制备了聚合的手性salen Mn（Ⅲ）配合物催化剂。聚合物结构中催化活性位的一维有序排列,能有效抑制催化活性中间体的二聚失活,有利于提高催化剂的稳定性。手性salen Mn（Ⅲ）聚合物在不对称催化苯乙烯环氧化反应体系中具有溶剂控制相转移功能,表现出与传统均相手性salen Mn（Ⅲ）配合物相当的催化活性与对映选择性。通过变换溶剂,催化剂从反应体系中异固体的形式析出,可重复使用3次以上。采用缩聚法,将具有溶剂可控分相功能的离子液体结构引入手性salen Mn（Ⅲ）聚合物结构中,制备了一类全新的离子液体功能化手性salen Mn（Ⅲ）聚合物催化剂。离子液体结构对催化活性中间体的稳定作用,使该催化剂表现出比均相催化剂更高的催化活性和对映选择性。利用离子液体在不同极性溶剂中溶解度的显著差异,通过简单的溶剂变换,实现了催化剂与反应体系的分离和重复使用。采用UV-vis光谱原位分析了离子液体功能化手性Salen Mn（Ⅲ）聚合物催化剂在不对称催化苯乙烯环氧化反应中的氧转移过程,实时跟踪了催化活性中间体[salen Mn（Ⅴ）=O]⁺的紫外特征吸收峰的变化,证实了离子液体对催化活性中间体[salen Mn（Ⅴ）=O]⁺具有稳定作用。基于离子液体的可控分相功能以及离子液体结构单元对催化活性中间体[salen Mn（Ⅴ）=O]⁺的稳定作用,采用轴向配位或共价键联法,将功能化离子液体从不同位置引入到手性salen Mn（Ⅲ）配合物结构中,制备了三种具有溶剂控制相转移功能的手性salen Mn（Ⅲ）配合物催化剂,考察了功能化离子液体结构单元在手性salen Mn（Ⅲ）结构中的不同接枝位置对催化剂性能的影响。离子液体赋予催化剂溶剂控制相转移功能,在苯乙烯不对称环氧化反应中,手性salen Mn（Ⅲ）配合物一端接枝离子液体结构单元的催化剂具有比均相催化剂更高的催化活性和对映选择性,通过溶剂调变,催化剂以固体的形式从反应体系中简单分离,且可重复使用10次以上。采用共价键联法将具有分相功能的咪唑类离子液体结构单元引入到传统手性Schiff VO（Ⅳ）配合物结构中,合成了离子液体功能化手性Schiff VO（Ⅳ）配合物,用FT-IR、UV-vis、EIS-MS对该配合物结构进行了表征。催化剂结构中离子液体的亲水性使该催化剂在以H₂O₂为氧化剂的硫醚不对称氧化反应中表现出比传统手性Schiff VO（Ⅳ）配合物催化剂更高的催化活性和对映选择性。反应完成后,加入正己烷,该催化剂可从反应体系中析出,表现出多相催化剂易分离的优点,且可重复使用6次以上。更多还原

【Abstract】 Chiral Schiff base complexes are excellent catalysts in the fields of asymmetric catalysis.However,the homogeneous complexes are not easily recovered for reuse or recycle and the heterogeneous catalysts often suffer from decrease of catalytic efficiency.To address the issue, attempts were made to develop novel kinds of chiral Schiff base complexes that can be used as highly effective solvent-regulated phase transfer catalyst in the corresponding catalytic reaction.The chiral Schiff base complexes with the attractive feature of tunable miscibility could be miscible with reaction medium and immiscible with extractant.So they acted as homogeneous catalyst in corresponding reaction system,leading to excellent catalytic activity.After completion of the reaction,the catalysts could be facilely separated from the reaction system by addition of another solvent that is immiscible with the catalyst,therefore,the catalysts could be precipitated from the system.The integration of reaction and separation made the catalysts perform as "one-phase catalysis and two-phase separation".A metal-organic assembly with quasi-salen Mn（Ⅲ） active structural units was synthesized via a process involving in situ self-assembly of linked 4,4’-methylenebis（6-（sec-butylimino）methyl） phenol) ligand with manganese ion.The synthesized quasi-salen Mn（Ⅲ） assembly showed typical properties of solvent-regulated phase transfer catalyst and high catalytic efficiency bearing comparison with homogeneous salen Mn（Ⅲ） catalyst in the epoxidation of unfunctionalized alkenes.Furthermore,it could be easily separated by simple phase separation techniques,and could be recovered easily by the addition of hexane and subsequently reused at least 8 times without loss of activity.Density functional theory （DFT） at the B3LYP level in Gaussian 03 programs was employed to evaluate the optimized geometries of the synthesized quasi-salen Mn（Ⅲ） assembly and confirmed the structural stability of the complex.A novel polymeric chiral salen Mn（Ⅲ） complex with chiral diamine bridging was synthesized.With larger molecular weight,it acted as a solvent-regulated phase transfer catalyst in the asymmetric epoxidation of styrene under the given reaction conditions.Compared with the homogeneous monomeric chiral salen Mn（Ⅲ） complex,it showed the similar yield and enantioselectivity of the epoxide.Under optimal reaction conditions,the yield and the enantioselectivity of the epoxide were as high as 98%and 47%ee,respectively.Moreover,the polymeric chiral salen Mn（Ⅲ） complex could be conveniently recovered from the products by control of the solvent and be reused at least 3 times without losses of both activity and enantioselectivity.A novel polymeric ionic liquid（IL）-functionalized chiral salen Mn（Ⅲ） complex was successful synthesised by covalently-polymerization between amino（-NH₂） group of 1,3-dipropylamineimidazolium bromide with chloromethyl（-CH₂Cl） group at two sides of 5,5’ positions in the salen ligand.The synthesized polymeric complex was totally miscible with dichloromethane but insoluble in non-polar organic solvents,thereby, could act as a "solvent-regulated phase transfer catalyst" in the enantioselective epoxidation of styrene.It showed comparable activity and enantioselectivity as a catalyst in asymmetric epoxidation of styrene relative to the monomeric chiral salen Mn（Ⅲ） complex and readily recovered from reaction system by simple precipitation.Moreover,with the catalytic site isolation of the rigid polymer framework,the polymeric chiral complex could be used at least 10 times without significant loss of catalytic activity and enantioselectivity.UV-vis spectra was used to monitor online the catalytic process and strongly supported the positive influence of the polarity of the IL on the stabilization of the transition state.Different strategies have been employed to attach the IL onto the chiral salen Mn（Ⅲ） complex to synthesize a novel series of IL-functionalized chiral salen Mn（Ⅲ） complex.The complexes with intriguing peculiarity of solubility are miscible with dichloromethane and insoluble in n-hexane.It therefore will work under homogeneous conditions during the reaction stage but will be precipitated at the end of the reaction by simple addition of n-hexane resulting in facile separation and reuse.The catalytic performances strongly depended on the attachment positions of chiral salen Mn（Ⅲ） complex with the IL.The complex prepared by the way of covalent linkage of the amino group in the IL with salen ligand at one side of 5 position showed the best catalytic performances in the epoxidation reaction and can be easily recovered for reuse at least 10 times.A novel hydrophilic IL of 1-propylamine-3-methylimidazolium tetrafluoroborate was covalently bonded onto chiral Schiff VO（Ⅳ） complex successfully.It was found that the IL-functionalized chiral Schiff VO（Ⅳ） complexes showed high activity and comparable enantioselectivity in asymmetric oxidation of the aryl methyl sulfides using hydrogen peroxide（30%） oxidant for its special ’hydrophilicity’ and the retention of homogenous reaction system.Moreover,it could be readily separated by the addition of hexane and thereby subsequently reused at least 6 times without loss of activity.Different substitutes have been employed at 3 position of the Schiff base ligand in order to investigate the effect of electronic properties on the catalytic performances of the complexes.As expected,the electronic properties of the ligand have a significant effect on the catalytic properties.更多还原