"Unlock-Lock" Approach to [2] and [3]Rotaxanes: Entering of a Ring through Disulfide Linkage That is Unlocked by Thiol "Key"

Bifunctional secondary ammonium salt bearing disulfide linkage at the center and bulky group at the both termini was mixed with dibenzo-24-crown-8. During reversible cleavage of the disulfide linkage catalyzed by benzenethiol, crown ether entered the disulfide linkage to afford corresponding [2] and [3]rotaxanes.