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Issue 7, 2019
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Rotational isomerism of the amide units in rotaxanes based on a cyclic tetraamide and secondary ammonium ions

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Abstract

In this study, we synthesized the macrocyclic tetraamide 1, possessing four tertiary amide units, as a host for mono- and bis-ammonium ions, forming corresponding [2]pseudorotaxanes stabilized through hydrogen bonding between the components. [2]Rotaxanes comprising 1 as the macrocycle and mono- and bis-ammonium ions as the axle components were synthesized through imine bond formation. The tetraamide 1 exists as a mixture of rotamers in solution; in the [2]rotaxanes, however, the conformation of this component was controlled through intramolecular hydrogen bonding between the axle and macrocyclic components. In a nonpolar solvent (CDCl3), only one conformational isomer existed for each [2]rotaxane. On the other hand, in a polar solvent (DMSO-d6), the [2]rotaxane possessing a mono-ammonium ion in the axle was partially isomerized; only a single rotational isomer existed for the [2]rotaxane featuring a bis-ammonium ion in the axle, because of a complete set of hydrogen bonds, in this polar solvent.

Graphical abstract: Rotational isomerism of the amide units in rotaxanes based on a cyclic tetraamide and secondary ammonium ions

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Publication details

The article was received on 21 Jan 2019, accepted on 19 Feb 2019 and first published on 20 Feb 2019


Article type: Research Article
DOI: 10.1039/C9QO00096H
Org. Chem. Front., 2019,6, 1002-1009

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    Rotational isomerism of the amide units in rotaxanes based on a cyclic tetraamide and secondary ammonium ions

    Y. Okuma, T. Tsukamoto, T. Inagaki, S. Miyagawa, M. Kimura, M. Naito, H. Takaya, T. Kawasaki and Y. Tokunaga, Org. Chem. Front., 2019, 6, 1002
    DOI: 10.1039/C9QO00096H

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