Template synthesis of [2]rotaxanes with large ring components and tris(biphenyl)methyl group as the blocking group. The relationship between the ring size and the stability of the rotaxanes.

We synthesized a series of macrocyclic phenanthrolines 3a-e and a tris(biphenyl)methyl derivative 4. [2]Rotaxanes with large ring components (10a,b) were synthesized by the template method, and the stability of the rotaxanes was examined. The study revealed that the tris(biphenyl)methyl group is an effective blocking group for the rotaxanes with up to a 33-membered ring. Even a rotaxane with a 37-membered macrocyclic phenanthroline (10b) could be isolated. The dissociation of 10b occurred at 60 degrees C.