School of Chemistry and Chemical Engineering and State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, 200240, Shanghai, China.
Department of Chemical and Biomolecular Engineering, National University of Singapore, Singapore, 117576, Singapore.
Nat Commun. 2018 Oct 24;9(1):4423. doi: 10.1038/s41467-018-06872-0.
The search for supramolecular reactors that contain no catalytically active sites but can promote chemical transformations has received significant attention, but it remains a synthetic challenge. Here we demonstrate a strategy of incorporating bulky and electro-rich aromatic linkers into metallocages to induce cascade reactions. Two hexahedral cages with a framework formula [(ZnL)(OTf)] are assembled from six tetrakis-bidentate ligands derived from tetraphenylethylene and eight zinc(II)tris(pyridylimine) centers. The cage cavities can accommodate different molecules such as anthranilamide and aromatic aldehyde through supramolecular interactions, allowing for a cascade condensation and cyclization to produce nonplanar 2,3-dihyroquinazolinones. The reaction is highly efficient with high rate enhancements (up to k/k = 38,000) and multiple turnovers compared to the bulk reaction mixture. Control experiments and molecular simulations suggest that the acceleration is attributed to inherent strength of binding affinity for reactants and the release of products to establish catalytic turnover is due to the host-guest geometry discrepancy.
寻找不含催化活性位点但能促进化学反应的超分子反应器引起了广泛关注，但这仍然是一个合成挑战。在这里，我们展示了一种将大体积和富电子芳香族连接物纳入金属笼以引发级联反应的策略。两个具有框架式[(ZnL)(OTf)]的六方笼由六个衍生自四苯乙烯的四齿双齿配体和八个锌（II）三（吡啶亚胺）中心组装而成。笼腔可以通过超分子相互作用容纳不同的分子，如邻苯二甲酰亚胺和芳香醛，从而进行级联缩合和环化，生成非平面的 2,3-二氢喹唑啉酮。与体相反应混合物相比，该反应具有很高的效率，具有很高的速率增强（高达 k/k=38,000）和多次周转。控制实验和分子模拟表明，加速是由于反应物的固有结合亲和力强度以及产物释放以建立催化周转，这是由于主客体几何形状差异所致。
