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- Title
C<sub>3</sub>-Symmetric Boron Lewis Acid with a Cage-Shape for Chiral Molecular Recognition and Asymmetric Catalysis.
- Authors
Konishi, Akihito; Nakaoka, Koichi; Maruyama, Hikaru; Nakajima, Hideto; Eguchi, Tomohiro; Baba, Akio; Yasuda, Makoto
- Abstract
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.
- Subjects
LEWIS acids; CHIRAL recognition; CATALYSIS; BORATES; X-ray crystallography; SULFOXIDES
- Publication
Chemistry - A European Journal, 2017, Vol 23, Issue 6, p1273
- ISSN
0947-6539
- Publication type
Article
- DOI
10.1002/chem.201605712