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High‐Yield Diastereoselective Synthesis of Planar Chiral [2]‐ and [3]Rotaxanes Constructed from per‐Ethylated Pillar[5]arene and Pyridinium Derivatives
Author(s) -
Ogoshi Tomoki,
Yamafuji Daiki,
Aoki Takamichi,
Kitajima Keisuke,
Yamagishi Tadaaki,
Hayashi Yoshihiro,
Kawauchi Susumu
Publication year - 2012
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201200122
Subject(s) - rotaxane , pyridinium , chemistry , enantiomer , enantiopure drug , yield (engineering) , stereochemistry , supramolecular chemistry , crystallography , materials science , polymer chemistry , medicinal chemistry , organic chemistry , crystal structure , enantioselective synthesis , catalysis , metallurgy
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.