手性鋁陽離子在催化領域之應用

Chiral Aluminum Cations in Catalysis

許靖北(Ching-Pei Hsu)

指導教授 ： 邱靖雯

國立臺灣大學/理學院/化學研究所/碩士(2022年)

https://doi.org/10.6342/NTU202102966

摘要

雖然鋁陽離子的催化應用已被廣泛討論，手性鋁陽離子的相關研究卻相當少。在這篇論文中，我們合成了兩種不同配位數的鋁陽離子，並檢視它們的催化活性。第一個是含有一對脯氨醇衍伸配基、並具有C2-對稱的手性四配位鋁陽離子[3][X]，此四配位鋁陽離子不僅可用市售化學品於兩步驟中合成，且於競爭實驗中被證實其酸性高於常見強路易士酸B(C6F5)3，也在初步催化反應研究中發現，[3][X]確實可以有效率地催化酮的硼氫化還原、狄耳士-阿爾德反應、麥可加成反應，並展現中等的立體選擇性。為了挑戰更不容易進行的不對稱催化反應，如：烯類的不對稱還原，我們也重新設計新的鋁陽離子催化劑，合成了一系列有芳基取代之雙(噁唑啉)配基之四配位鋁錯合物(19、22、23)，以及其對應的三配位烷基鋁陽離子[24][X]，這些三配位鋁陽離子皆擁有高路易士酸性以及C2-對稱手性，有潛力作為烯類的不對稱官能基化和亞胺的不對稱氫化的催化劑。

關鍵字

鋁陽離子 ； 不對稱催化 ； 路易士酸 ； 脯氨醇 ； 雙(噁唑啉)

並列摘要

Although the application of cationic aluminum complexes in catalysis has been extensively investigated, the incorporation of aluminum cations into chiral environments is less explored. In this work, a C2-symmetric chiral tetra-coordinate aluminum cation [3][X] bearing two prolinol-derived ligands was prepared from commercially available starting materials in two steps. The high Lewis acidity of [3][X], exceeded that of B(C6F5)3, was verified by a competition binding experiment. Preliminary catalytic activity studies of [3][X] revealed that the tetra-coordinate aluminum cation is effective in accomplishing high conversion in ketone hydroboration, Diels-Alder reaction, and Michael addition with moderate enantioselectivity. To further explore the possibilities of aluminum cations in catalyzing challenging transformations such as asymmetric olefin reduction, a series of C2-symmetric chiral tetra-coordinate aluminum complexes bearing aryl-substituted bisoxazoline ligands were prepared (19, 22, and 23). Subsequently, the related tri-coordinate alkyl aluminum cations [24][X] were successfully generated. These highly Lewis acidic cationic complexes have the potential to catalyze asymmetric olefin functionalization and imine hydrogenation.

並列關鍵字

aluminum cation ； asymmetric catalysis ； Lewis acid ； prolinol ； bis(oxazoline)

參考文獻

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