Advances in supramolecular
chemistry are often underpinned by the
development of fundamental building blocks and methods enabling their
interconversion. In this work, we report the use of an underexplored
dynamic covalent reaction for the synthesis of stimuli-responsive
[2]rotaxanes. The formamidinium moiety lies at the heart of these
mechanically interlocked architectures, because it enables both dynamic
covalent exchange and the binding of simple crown ethers. We demonstrated
that the rotaxane self-assembly follows a unique reaction pathway
and that the complex interplay between crown ether and thread can
be controlled in a transient fashion by addition of base and fuel
acid. Dynamic combinatorial libraries, when exposed to diverse nucleophiles,
revealed a profound stabilizing effect of the mechanical bond as well
as intriguing reactivity differences between seemingly similar [2]rotaxanes.
In this article, we explore the scope of a largely overlooked dynamic covalent reaction – amidinium exchange – and report on conditions that allow formal amidinium metathesis reactions.
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