Using "threading followed by shrinking" to synthesize highly stable dialkylammonium-ion-based rotaxanes.

Herein, we report a "threading followed by shrinking" approach for the synthesis of rotaxanes by using an "oxygen-deficient" macrocycle that contained two arylmethyl sulfone units and the dumbbell-shaped salt bis(3,5-dimethylbenzyl)ammonium tetrakis(3,5-trifluoromethylphenyl)borate as the host and guest components, respectively. The extrusion of SO2 from both of the arylmethyl sulfone units of the macrocyclic component in the corresponding [2]pseudorotaxane resulted in a [2]rotaxane that was sufficiently stable to maintain its molecular integrity in CD3 SOCD3 at 393 K for at least 5 h.