Chemical Modification of Amide-Based Catenanes and Rotaxanes II. Synthesis of tertiary Amine [2]Catenanes and [2] Rotaxanes via N-Methylation Followed by Borane Reduction of secondary Amide [2]Catenanes and [2]Rotaxanes and Mobility of Their Components

Abstract

Abstract Secondary amide [2]catenane 1a was converted to the corresponding tertiary amide [2]catenane 1b by repetitive treatment with a methylating system of CH3I and KOH in DMSO. The amide functions of 1b were reduced with borane in refluxing THF to give the corresponding tertiary amine [2]catenane 1c. Their structures were characterized by NMR, IR, and FAB-MS spectroscopies. An X-ray crystallographic analysis of 1c showed that its solid-state structure was stabilized by a CH–π interaction between the p-xylylene and m-xylylene units, together with a π–π stacking interaction between the two m-xylylene units. A variable temperature 1H NMR study suggested that 1c had components of highly enhanced mobility in CDCl3, even at lower temperature, although a much weaker interaction, such as the CH–π interaction, existed between their components in solution. Tertiary amine [2]rotaxane 3c was obtained from the corresponding secondary amide [2]rotaxane 3a by a procedure similar to that used for 1a. The 1H NMR spectra indicated that the mobility of the components of 3c is sufficiently high even at lower temperature.