Wang Kaixuan, Tang Xianhui, Anjali Bai Amutha, Dong Jinqiao, Jiang Jianwen, Liu Yan, Cui Yong
School of Chemistry and Chemical Engineering, Frontiers Science Center for Transformative Molecules and State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240, P. R. China.
Department of Chemical and Biomolecular Engineering, National University of Singapore, Singapore 117576, Singapore.
J Am Chem Soc. 2024 Mar 13;146(10):6638-6651. doi: 10.1021/jacs.3c12555. Epub 2024 Feb 28.
Covalent organic cages are a prominent class of discrete porous architectures; however, their structural isomerism remains relatively unexplored. Here, we demonstrate the structural isomerism of chiral covalent organic cages that renders distinct enantioselective catalytic properties. Imine condensations of tetra-topic 5,10-di(3,5-diformylphenyl)-5,10-dihydrophenazine and ditopic 1,2-cyclohexanediamine produce two chiral [4 + 8] organic cage isomers with totally different topologies and geometries that depend on the orientations of four tetraaldehyde units with respect to each other. One isomer () has an unprecedented Johnson-type structure, whereas another () adopts a tetragonal prismatic structure. After the reduction of the imine linkages, the cages are transformed into two amine bond-linked isomers and . After binding to Ni(II) ions, both can serve as efficient catalysts for asymmetric Michael additions, whereas affords obviously higher enantioselectivity and reactivity than presumably because of its large cavity and open windows that can concentrate reactants for the reactions. Density-functional theory (DFT) calculations further confirm that the enantioselective catalytic performance varies depending on the isomer.
共价有机笼是一类重要的离散多孔结构；然而，它们的结构异构现象仍相对未被充分探索。在此，我们展示了手性共价有机笼的结构异构现象，这种异构导致了截然不同的对映选择性催化性质。四齿的5,10-二(3,5-二甲酰基苯基)-5,10-二氢吩嗪与双齿的1,2-环己二胺进行亚胺缩合反应，生成两种具有完全不同拓扑结构和几何形状的手性[4 + 8]有机笼异构体，这取决于四个四醛单元彼此之间的取向。一种异构体（）具有前所未有的约翰逊型结构，而另一种异构体（）则采用四方棱柱结构。在亚胺键还原后，笼状结构转变为两种胺键连接的异构体 和 。与Ni(II)离子结合后，两者都可作为不对称迈克尔加成反应的高效催化剂，然而， 比 表现出明显更高的对映选择性和反应活性，这可能是由于其较大的空腔和开放窗口能够使反应物聚集以进行反应。密度泛函理论（DFT）计算进一步证实，对映选择性催化性能因异构体而异。
