He Ting, Liu Ruoyang, Wang Shihuai, On Ivan Keng Wee, Wu Yinglong, Xing Yi, Yuan Wei, Guo Jingjing, Zhao Yanli
School of Chemistry, Chemical Engineering and Biotechnology, Nanyang Technological University, Singapore 637371, Singapore.
Department of Chemistry, Faulty of Science, National University of Singapore, Singapore 117543, Singapore.
J Am Chem Soc. 2023 Aug 16;145(32):18015-18021. doi: 10.1021/jacs.3c05732. Epub 2023 Aug 8.
The development of chiral covalentorganic framework catalysts (CCOFs) to synthesize enantiopure organic compounds is crucial and highly desirable in synthetic chemistry. Photocatalytic asymmetric reactions based on CCOFs are eco-friendly and sustainable while they are still elaborate. In this work, we report a general bottom-up strategy to successfully synthesize several photoactive CCOFX (X = 1-5 and 1-Boc). The photoactive porphyrin building blocks are selected as knots and various secondary-amine-based chiral catalytic centers are immobilized on the pore walls of CCOFX through a rational design of benzoimidazole linkers. The porphyrin units act as light-harvesting antennae to generate photo-induced charge carriers for the activation of bromide during the photocatalytic asymmetric alkylation of aldehydes. Meanwhile, various aldehydes are activated by the chiral secondary amine to form the target products with a high yield (up to 97%) and ee value (up to 93%). The results significantly expand the scope to predesign CCOF photocatalysts for visible-light-driven asymmetric catalysis.
开发用于合成对映体纯有机化合物的手性共价有机框架催化剂（CCOFs）在合成化学中至关重要且极具吸引力。基于CCOFs的光催化不对称反应既环保又可持续，尽管它们仍很精细。在这项工作中，我们报告了一种通用的自下而上策略，成功合成了几种光活性CCOF-X（X = 1-5和1-Boc）。选择光活性卟啉构建块作为节点，并通过合理设计苯并咪唑连接体，将各种基于仲胺的手性催化中心固定在CCOF-X的孔壁上。在醛的光催化不对称烷基化过程中，卟啉单元充当光捕获天线，生成光生电荷载流子以激活溴化物。同时，各种醛被手性仲胺活化，以高收率（高达97%）和对映体过量值（高达93%）形成目标产物。这些结果显著扩展了预设计用于可见光驱动不对称催化的CCOF光催化剂的范围。
