title: High-yield diastereoselective synthesis of planar chiral [2]- and [3]rotaxanes constructed from per-ethylated pillar[5]arene and pyridinium derivatives.
abstract: Planar chiral [2]- and [3]rotaxanes constructed from pillar[5]arenes as wheels and pyridinium derivatives as axles were obtained in high yield using click reactions. The process of rotaxane formation was diastereoselective; the obtained [2]rotaxane was a racemic mixture consisting of (pS, pS, pS, pS, pS) and (pR, pR, pR, pR, pR) forms of the per-ethylated pillar[5]arene (C2) wheel, and other possible types of the [2]rotaxane did not form. Isolation of the enantiopure [2]rotaxanes with one axle through (pS, pS, pS, pS, pS)-C2 or (pR, pR, pR, pR, pR)-C2 wheels was accomplished. Furthermore, pillar[5]arene-based [3]rotaxane was successfully synthesized by attachment of two pseudo [2]rotaxanes onto a bifunctional linker. [3]Rotaxane formed in a 1:2:1 mixture with one axle threaded through two (pS, pS, pS, pS, pS)-C2, one (pS, pS, pS, pS, pS)-C2 and one (pR, pR, pR, pR, pR)-C2 (meso form), or two (pR, pR, pR, pR, pR)-C2 wheels. The [3]rotaxane enantiomers and the meso form were successfully isolated using appropriate chiral HPLC column chromatography. The procedure developed in this study is the starting point for the creation of pillar[5]arene-based interlocked molecules.
authors.affiliation: Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa, 920-1192, Japan. ogoshi@t.kanazawa-u.ac.jp
authors.forename: Tomoki
authors.initials: T
authors.lastname: Ogoshi
authors.forename: Daiki
authors.initials: D
authors.lastname: Yamafuji
authors.forename: Takamichi
authors.initials: T
authors.lastname: Aoki
authors.forename: Keisuke
authors.initials: K
authors.lastname: Kitajima
authors.forename: Tada-aki
authors.initials: TA
authors.lastname: Yamagishi
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Hayashi
authors.forename: Susumu
authors.initials: S
authors.lastname: Kawauchi