Template-Directed Synthesis and Isolation of Unimolecular Oligo[n]catenanes Using a One-Pot CuAAC “Click” Reaction Approach

Within the field of mechanically interlocked molecules, catenanes have garnered much interest in the past few decades due to their chain-like architecture of interlocked molecular rings. This interest stems from their unique properties and degrees of freedom that are distinct in comparison to traditional molecular architectures, a fact that makes catenanes potentially attractive building blocks in the construction of next-generation polymeric materials. Most approaches to make unimolecular [n]catenanes are either low yielding or are laborious, often relying on multistep pathways for preparation and purification. Therefore, developing efficient syntheses for [n]catenanes remains an important challenge for chemists. Here, we describe a template-directed one-pot approach that overcomes the limitations of multistep syntheses by using simple, symmetrical phenanthroline-based building blocks and CuAAC “click” chemistry to yield a series of unimolecular [n]catenanes. This methodology relies on simultaneous copper(I)-based templation and click chemistry, ultimately resulting in a one-pot synthetic strategy to make either a [2]catenane in high yield (82%) or a batch of well-defined linear [2]–[5]catenanes (and trace amounts of a [6]catenane) in an 18% overall yield, depending on the rate of addition of the alkyne- and azide-functionalized precursors (i.e., slowly or all at once). Such kinetic control represents a potential pathway toward the preparation of higher-order [n]catenanes capable of further chain extension using very simple precursors.