Chemical modification of amide-based catenanes and rotaxanes I.: Synthesis of secondary amine [2]catenanes and [2]rotaxanes by the borane reduction of secondary amide [2]catenanes and [2]rotaxanes and mobility of their components

Various secondary amine [2]catenanes and [2]rotaxane were prepared by borane reduction of the corresponding secondary amide [2]catenanes and [2]rotaxane. Their structures were characterized by NMR, IR, and FAB-MS spectroscopies. The mobility of the components in solution was examined by H-1 NMR spectroscopy. The substituents on the isophthaloyl units of the catenanes prevented complete circumrotation of the macrocydic components ("half rotation"). On the other hand, macrocyclic ring components bearing unsubstituted isophthaloyl units completely circumrotated through the other faster than on the H-1 NMR time scale ("full rotation"). In the case of the secondary amine [2]catenanes, no hydrogen bonding interaction between the secondary amino groups was observed. A dynamic H-1 NMR study showed a highly enhanced mobility of the components of the secondary amine [2]catenanes and [2]rotaxane compared with the corresponding amide compounds, even at lower temperature.