Now, writing in Communications Chemistry, Alberto Martinez-Cuezva, Jose Berna and co-workers report the formation of polyamide-based rotaxanes using a conjugated bis(enaminone) template. “We incorporate a double bond between the nitrogen and carbon atoms of the two amide functions in a fumaramide, with the aim of improving the acceptor ability of the oxygen atoms in the templates,” says Berna. The bis(enaminone) thread directs the ring-closing reaction and formation of a benzylic amide-containing rotaxane in a five-component clipping reaction. This [2]rotaxane synthesis proceeds with complete conversion and in yields of up to 92%.In the solid state, X-ray crystallographic analysis reveals that the bis(enaminone) thread of the rotaxane forms two intramolecular hydrogen bonds with the macrocycle causing the macrocyclic cavity to distort and form two intermolecular hydrogen bonds between the macrocycles of neighbouring molecules (pictured). The thread is planar and highly stable in the rotaxane.
