Self-assembling [2]- And [3]rotaxanes from secondary dialkylammonium salts and crown ethers

The self-assembly of three new rotaxanes - two [2]rotaxanes and a [3]rotaxane - formed by a "threading followed by stoppering" approach is described. These template-directed syntheses rely on the formation of pseudorotaxane intermediates, which self-assemble in solution from functionalized secondary dialkylammonium hexafluorophosphate threads and macrocyclic polyether rings (either dibenzo[24]crown-8 or its asymmetric constitutional isomer). The stoppers - substituted 1,2,3-triazoles - were created by thermally allowed 1,3-dipolar cycloadditions between azido groups, which terminate the threads, and di-tert-butyl acetylenedicarboxylate.