基于多金属氧酸盐的手性金属有机框架在不对称催化缺电子烯烃环氧化中的应用

Catalytic asymmetric process that exhibit high activity, selectivity and broad substrate generality under mild reaction conditions, are indispensable for producing enantiomerically enriched compounds in modern organic synthesis. Epoxidation is a key bond-forming reaction in nature and in the repertoire of the synthetic chemist, and the development of reusable heterogeneous catalyst performing high efficiency and excellent stereoselectivity of this reaction under mild conditions is chemists’ pursuit. The major aim of this project is to produce the rich optical site of epoxy ketones (aldehydes), which are the important intermediates in the pharmaceutical and natural product synthesis. Chiral metal−organic frameworks (MOFs) with porous and tunable nature have made them feasible to perform a variety of chemical reactions as heterogeneous asymmetric catalysts. One of the most extraordinary features of MOFs is that delicate functional groups either enantiopure organic ligands or their metal complexes can be blended directly via self-assembly, endowing them with multiple functionalities and new features distinctively different from the components. By incorporating chiral organocatalytic group and oxidation catalyst into a single framework, homochiral POM/ MOFs reaction platforms with asymmetric oxidation catalytic function will be obtained and explored in the asymmetric epoxidation of electron-deficient olefins. The coexistence of the chiral organo-catalysts and the oxidants within a confined space provided a special environment for the formation of reaction intermediates in a stereoselective fashion with high selectivity. In order to realize the substrate molecule high selective recognition and geometric position limit in the MOFs’ provided special space limitation, and complete asymmetric epoxy chemical reaction of specific electron-deficient olefin，the most important issue is to matach stereo, electronic effect between "chiral ligands – POM – substrate" by checking the impact of MOFs with different geometric configurations, catalytic activity site layouts and space orientations on the catalytic reaction. By probing into its catalytic mechanism, to develope a new train of thought for the high efficiency and high enantioselective preparation of the electron-deficient epoxy compounds.

环氧化反应在合成化学中占有非常重要地位，发展可重复利用的非均相催化剂，在温和条件下完成高效高选择性的反应是化学家们一直追求的目标。本项目以制备在制药和天然产物合成中具有重要应用价值的富有光学位点的环氧酮（醛）为目标，借鉴手性金属有机框架(MOFs)在非均相催化中的研究思路，将多金属氧酸盐(POMs)和手性催化功能基团引入到精心设计的MOFs中，制备具有不对称氧化催化功能的手性POM/ MOFs反应平台，开展在非均相条件下催化缺电子烯烃环氧化反应。考查MOFs中催化活性位点的布局和空间取向对催化反应的影响，调控“手性配体—POM—底物”之间立体、电子效应的匹配，以期发挥MOFs结构内部孔道提供的特殊空间限制，实现对底物分子的高选择性识别和几何位置的限定，完成对特定缺电子烯烃的不对称环氧化反应。探究其催化机理，为实现高效率、高对映选择性制备缺电子环氧化物的实际应用拓展新的研究思具路。

富有光学位点的环氧酮（醛）具有可功能化的羰基和环氧基，可以作为医药、农药及功能材料的前驱体和中间体，在精细化工生产中占有极为重要的地位。发展具有高效、高对映选择性的非均相催化剂，开展高效和绿色化等特点的串联反应合成策略已成为有机合成化学研究的前沿领域之一。本项目借鉴手性金属有机框架在非均相催化中的研究思路，将多金属氧酸盐和手性催化功能基团引入到精心设计的MOFs中，制备具有不对称氧化催化功能的手性POMOFs反应平台，开展在非均相条件下催化缺电子烯烃环氧化反应。本项目得到的成果如下:.1）.在水热条件下将手性配体L/D-PYI、ZnW12O406-构筑块，引入到以锌离子和3-氨基-4,4'-联吡啶构筑的MOF中，得到具有3D结构的对映体催化剂ZnW−PYI1和ZnW−PYI2，通过手性吡咯烷、氨基、配位不饱和金属离子和多酸多催化位点协同作用实现了由烯烃到环碳酸酯的连串反应，得到大于90%的产率和85%的ee值。.2）.在水热条件下将手性配体L/D-PYI、[PW12O40]3-构筑单元和Cu2+离子得到一对具有二维Kagomé网格结构的对映体催化剂CuPYI1和CuPYI2。在催化-不饱和酮(醛)的环氧化反应中体现了完美的协同效果，得到约80%转化率和85% ee值，而且还实现了由小分子醛和酮经羟醛缩合反应和环氧化串联反应直接制备手性环氧酮。.3）.以[W10O32]4−、Cu(NO3)2•6H2O和4,4’-bipyidine为原料在水热反应条件下，首次得到基于独立结构的同多酸簇{H2W11O38}的无机-有机杂化材料{[Cu2(bpy)(H2O)5.5]2 [H2W11O38]•3H2O•0.5CH3CN}，该POMOF作为Lewis酸催化剂有效促进醛的硅腈化反应，得到大于90%的产率。.4）.以[As2W19O67(H2O)]14−、NiCl2•6H2O和phen为原料在水热反应条件下，制备了基于新型Dawson型阴离子簇的无机-有机杂化材料[Ni(phen)3]4[As2W18O60]{[Ni(phen)2] [H2As2W18O60]}•12H2O。运用新的合成策略设计合成得到新型的具有As•••As相互作用的Dawson型多酸簇β [W18O54(AsO3)2]6−。该化合物具有良好的光催化性质，在可见光下可以有效降解罗丹明等染料。