Enantiopure Assembly of M4L6 Supramolecular Clusters with Different Sizes and their Application to Asymmetric Organic Reactions

在过去的几十年里，限制在超分子结构空腔内的反应的性能已经成为一种新的选择性催化体系的方法。1998年首次报道，Raymond和他的同事合成了一种具有[Ga4L6]12化学计量比的超分子主体络合物。这种组装体已被用作超分子催化剂，从而提高了反应速度和选择性。然而，尽管这类催化剂具有多功能性，但它们在不对称催化中的应用仍然是一个重要的目标。在罗伯特·伯格曼教授和迪恩·托斯特教授的密切合作下，我正在雷蒙德教授小组的两个项目中工作，以扩展M4L6四面体的丰富化学。我成功地合成了一种主链上含有氨基酸的新型对映体配体。相应的较大的对映体四面体的结构和催化研究目前正在进行中。在第二个项目中，探索了[Ti4L6]8-和[Ge4L6]8-的还原电荷自组装的较不成熟的化学。成功地合成了这两个簇合物，并首次利用微波辅助自组装方法合成了Ti4L6四面体。为了比较[Ge4L6]8-和[Ga4L6]12-的催化效率，目前正在进行以超分子为模型的氮杂-钴重排反应。这将回答一个尚未解决的问题，即超分子笼的电荷是否影响其催化效率。

In the past decades, the performance of reactions constrained within the cavity of supramolecular structures has emerged as a novel approach toward selective catalytic systems. Initially reported in 1998, Raymond and co-worker synthesized a supramolecular host complex having [Ga4L6]12- stoichiometry. This assembly has been employed as a supramolecular catalyst resulting in increased reaction rates and improved selectivity. However, despite the versatility of this class of catalysts, their application in asymmetric catalysis remains an important goal. In close collaboration with Professor Robert Bergman and Professor Dean Toste, I am working on two projects in the group of Professor Raymond to extend this rich chemistry of M4L6 tetrahedron. I successfully synthesized a novel enantiopure ligand which incorporates amino acids in its backbone. Structural and catalytic studies of the corresponding larger and enantiopure tetrahedron are currently under investigation. In the second project, the less established chemistry of the reduced charge self-assemblies [Ti4L6]8- and [Ge4L6]8- are explored. Both cluster were successfully synthesized and a microwave -assisted self-assembly procedure was used for the first time to synthesize the Ti4L6 tetrahedron. In order to compare the catalytic efficiencies of [Ge4L6]8- and [Ga4L6]12-, a supramolecular-mediated Aza-Cope rearrangement as model reaction is currently underway. This will answer the yet open question whether the charge of supramolecular cage influences its catalytic efficiency.