School of Chemistry and Chemical Engineering and State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai, 200240, China.
Collaborative Innovation Center of Chemical Science and Engineering, Tianjin, 300072, China.
Nat Commun. 2019 Feb 5;10(1):600. doi: 10.1038/s41467-019-08416-6.
The search for porous materials with strong Brønsted acid sites for challenging reactions has long been of significant interest, but it remains a formidable synthetic challenge. Here we demonstrate a cage extension strategy to construct chiral permanent porous hydrogen-bonded frameworks with strong Brønsted acid groups for heterogeneous asymmetric catalysis. We report the synthesis of two octahedral coordination cages using enantiopure 4,4',6,6'-tetra(benzoate) ligand of 1,1'-spirobiindane-7,7'-phosphoric acid and Ni/Co-p-tert-butylsulfonylcalix[4]arene clusters. Intercage hydrogen-bonds and hydrophobic interactions between tert-butyl groups direct the hierarchical assembly of the cages into a permanent porous material. The chiral phosphoric acid-containing frameworks can be high efficient and recyclable heterogeneous Brønsted acid catalysts for asymmetric [3+2] coupling of indoles with quinone monoimine and Friedel-Crafts alkylations of indole with aryl aldimines. The afforded enantioselectivities (up to 99.9% ee) surpass those of the homogeneous counterparts and compare favorably with those of the most enantioselective homogeneous phosphoric acid catalysts reported to date.
寻找具有强布朗斯特酸位的多孔材料用于具有挑战性的反应一直是人们关注的焦点，但这仍然是一个艰巨的合成挑战。在这里，我们展示了一种笼状扩展策略，用于构建具有强布朗斯特酸基团的手性永久多孔氢键框架，用于非均相不对称催化。我们报道了使用手性纯 1,1'-螺[茚烷-7,7'-磷酸]的 4,4',6,6'-四（苯甲酸酯）配体和 Ni/Co-p-叔丁基砜杯[4]芳烃簇合成了两个八面体配位笼。笼间氢键和叔丁基之间的疏水相互作用指导笼的分级组装成永久多孔材料。含手性磷酸的框架可以作为高效和可回收的非均相布朗斯特酸催化剂，用于吲哚与醌单亚胺的不对称 [3+2]偶联以及吲哚与芳基亚胺的弗里德尔-克拉夫茨烷基化反应。所获得的对映选择性（高达 99.9%ee）超过了均相对应物的对映选择性，并与迄今为止报道的最对映选择性的均相磷酸催化剂相媲美。
