Issue 7, 2019

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

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

Supplementary files

Article information

Article type
Research Article
Submitted
21 Jän 2019
Accepted
19 Feb 2019
First published
20 Feb 2019

Org. Chem. Front., 2019,6, 1002-1009

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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