title: C3-Symmetric Boron Lewis Acid with a Cage-Shape for Chiral Molecular Recognition and Asymmetric Catalysis.
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.
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan.|Center for Atomic and Molecular Technologies, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan.
authors.forename: Akihito
authors.identifier: http://orcid.org/0000-0002-3438-786X
authors.initials: A
authors.lastname: Konishi
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Nakaoka
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan.
authors.forename: Hikaru
authors.initials: H
authors.lastname: Maruyama
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan.
authors.forename: Hideto
authors.initials: H
authors.lastname: Nakajima
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Eguchi
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan.
authors.forename: Akio
authors.initials: A
authors.lastname: Baba
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871, Japan.
authors.forename: Makoto
authors.identifier: http://orcid.org/0000-0002-6618-2893
authors.initials: M
authors.lastname: Yasuda
keywords: binaphthyl; cage-shaped borate; chiral Lewis acid; chiral molecular recognition; hetero-Diels-Alder reaction