One-Pot Synthesis of a Linear [4]Catenate Using Orthogonal Metal Templation and Ring-Closing Metathesis

The efficient synthesis of well-defined, linear oligocatenanes possessing multiple mechanical bonds remains a formidable challenge in the field of mechanically interlocked molecules. Here, a one-pot synthetic strategy is described to prepare a linear [4]catenate using orthogonal metal templation between a macrocycle precursor, composed of terpyridine and phenanthroline ligands spaced by flexible glycol linkers, and a closed phenanthroline-based molecular ring. Implementation of two simultaneous ring-closing metathesis reactions after metal complexation resulted in the formation of three mechanical bonds. The linear [4]catenate product was isolated in 55% yield as a mixture of topological diastereomers. The intermediate metal complexes and corresponding interlocked products (with and without metals) were characterized by nuclear magnetic resonance, mass spectrometry, gel permeation chromatography, and UV-vis absorption spectroscopy. We envision that this general synthetic strategy may pave the way for the synthesis of higher order linear oligocatenates/catenanes with precise molecular weights and four or more interlocking molecular rings.