Chen Xu, Jiang Hong, Li Xu, Hou Bang, Gong Wei, Wu Xiaowei, Han Xing, Zheng Fanfan, Liu Yan, Jiang Jianwen, Cui Yong
School of Chemistry and Chemical Engineering and State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai, 200240, China.
Department of Chemical and Biomolecular Engineering, National University of Singapore, Singapore, 117576, Singapore.
Angew Chem Int Ed Engl. 2019 Oct 7;58(41):14748-14757. doi: 10.1002/anie.201908959. Epub 2019 Sep 5.
Chiral phosphoric acids are incorporated into indium-based metal-organic frameworks (In-MOFs) by sterically preventing them from coordination. This concept leads to the synthesis of three chiral porous 3D In-MOFs with different network topologies constructed from three enantiopure 1,1'-biphenol-phosphoric acid derived tetracarboxylate linkers. More importantly, all the uncoordinated phosphoric acid groups are periodically aligned within the channels and display significantly enhanced acidity compared to the non-immobilized acids. This facilitates the Brønsted acid catalysis of asymmetric condensation/amine addition and imine reduction. The enantioselectivities can be tuned (up to >99 % ee) by varying the substituents to achieve a nearly linear correlation with the concentrations of steric bulky groups in the MOFs. DFT calculations suggest that the framework provides a chiral confined microenvironment that dictates both selectivity and reactivity of chiral MOFs.
通过空间位阻防止手性磷酸参与配位，从而将其引入铟基金属有机框架（In-MOFs）中。这一概念促使合成了三种具有不同网络拓扑结构的手性多孔三维In-MOFs，它们由三种对映体纯的1,1'-联苯酚-磷酸衍生的四羧酸连接体构建而成。更重要的是，所有未配位的磷酸基团在通道内周期性排列，与未固定化的酸相比，其酸度显著增强。这有利于布朗斯特酸催化不对称缩合/胺加成和亚胺还原反应。通过改变取代基可调节对映选择性（高达>99% ee），以实现与MOFs中空间位阻较大基团浓度的近似线性相关。密度泛函理论计算表明，该框架提供了一个手性受限的微环境，决定了手性MOFs的选择性和反应活性。
