Enantioselective Cycloaddition of Styrenes with Aldimines Catalyzed by a Chiral Magnesium Potassium Binaphthyldisulfonate Cluster as a Chiral Brønsted Acid Catalyst

A chiral magnesium potassium binaphthyldisulfonate cluster, as a chiral Brønsted acid catalyst, was shown to catalyze an enantioselective cycloaddition of styrenes with aldimines for the first time. The strong Brønsted acidity of the catalyst precursors, which might dissolve drying agents and take up the leached Mg2+ and K+, serendipitously led to good enantioselectivity. Mechanistic aspects were supported by X-ray and ESI-MS analysis of the catalyst and a kinetics study of the reaction. Useful transformations to optically active 1,3-amino alcohols on a gram scale were also demonstrated.

本研究首次证实，手性镁钾联萘二磺酸簇（chiral magnesium potassium binaphthyldisulfonate cluster）作为手性布朗斯特酸催化剂（chiral Brønsted acid catalyst），可催化苯乙烯类化合物与亚胺的对映选择性环加成反应。该催化剂前驱体具备强布朗斯特酸性，可溶解干燥剂并结合浸出的Mg²+与K+，意外地获得了优异的对映选择性。通过对该催化剂的X射线衍射（X-ray）、电喷雾电离质谱（ESI-MS）分析以及反应动力学研究，为该反应的机理提供了实验支撑。此外，该催化体系还可实现克级规模下光学活性1,3-氨基醇的制备，展现出良好的应用价值。