C3-Symmetric Boron Lewis Acid with a Cage-Shape for Chiral Molecular Recognition and Asymmetric Catalysis
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- 作者：Dr. Akihito Konishi ; Koichi Nakaoka ; Hikaru Maruyama ; Dr. Hideto Nakajima ; Tomohiro Eguchi ; Prof. Dr. Akio Baba and Prof. Dr. Makoto Yasuda
- 刊名：Chemistry - A European Journal
- 出版年：2017
- 出版时间：January 26, 2017
- 年：2017
- 卷：23
- 期：6
- 页码：1273-1277
- 全文大小：1236K
- ISSN：1521-3765
文摘
Chiral Lewis acids play an important role in the precise construction of various types of chiral molecules. Here, a cage-shaped borate 2 was designed and synthesized as a chiral Lewis acid that possesses a unique C3-symmetric structure composed of three homochiral binaphthyl moieties. The highly symmetrical structure of 2 with homochirality was clearly elucidated by X-ray crystallographic analysis. The peculiar chiral environment of 2⋅THF exhibited chiral recognition of some simple amines and a sulfoxide. Moreover, the application of 2⋅THF to hetero-Diels–Alder reactions as a chiral Lewis-acid catalyst afforded the enantioselective products, which were obtained through an entropy-controlled pathway according to the analysis of the relationship between optical yield and reaction temperature. In particular, the robust chiral reaction field of 2⋅THF allowed the first example of an asymmetric hetero-Diels–Alder reaction with a simple diene despite the requirement of high temperature.