Sequence-Selective Synthesis of Rotacatenane Isomers.

Rotacatenane is an interlocked compound composed of two mechanically interlocked macrocyclic components, i.e., a [2]catenane, and one axle component. In this paper we describe the selective synthesis of isomeric rotacatenanes. Two [2]rotaxanes with different phenanthroline moieties were synthesized by the oxidative coupling of an alkyne with a bulky blocking group, which proceeded in the cavity of the macrocyclic phenanthroline-Cu complex. The metal template method was used to install another cyclic component: the tetrahedral Cu(I) complex, which was composed of a [2]rotaxane and an acyclic phenanthroline derivative, was synthesized, and the cyclization of the phenanthroline derivative gave the rotacatenane. The sequential isomers of rotacatenanes were distinguished by (1)H and (13)C NMR spectroscopy.

Synthesis of [3]Rotaxanes by the Combination of Copper-Mediated Coupling Reaction and Metal-Template Approach.

[3]Rotaxanes with two axle components and one ring component were synthesized by the combination of a coupling reaction using a transition-metal catalyst and a metal-template approach. Thus, [2]rotaxanes were prepared by the oxidative dimerization of alkyne promoted by macrocyclic phenanthroline-CuI complexes. The [2]rotaxane was reacted with a Cu(I) salt and an acyclic ligand to generate a tetrahedral Cu(I) complex. Metal-free [3]rotaxane was isolated by the end-capping reaction of the acyclic ligand, followed by the removal of Cu(I) ion. The stability of the tetrahedral Cu(I) complexes depended on the size of both the ring component and the acyclic ligand, which was correlated with the yield of the corresponding [3]rotaxane.

Synthesis of rotacatenanes by the combination of Cu-mediated threading reaction and the template method: the dual role of one ligand.

Rotacatenanes were synthesized by the catalytic reaction using a macrocyclic phenanthroline-CuI complex followed by the installation of another ring by the template method. In this approach, the size of the ring component of the rotaxane turns out to be a very important factor for the synthesis of rotacatenanes.