Mechanochemical Synthesis of Pillar[5]arene-based [c2]Daisy Chain Rotaxanes

The solvent-free mechanochemical acylation of pillar[5]arene-based daisy chain monomers bearing either an alcohol or an amine function has been investigated in details. These chemical transformations have been also carried out in solution for comparison purposes. Whereas stoppered [c2]daisy chain derivatives have been obtained from the amine monomer whatever the conditions, stoppered [c2]daisy chain derivatives could be only obtained from the corresponding alcohol under mechanochemical conditions. In this particular case, concentration effects are clearly beneficial when the reactions are performed under solvent-free conditions as daisy chain assemblies are effectively present in the solid state despite the very weak affinity of the 11-hydroxy-undecyl subunit for the pillar[5]arene moiety.