A general and efficient five-step one-pot procedure leading to nitrogen-bridgehead heterocycles containing an imidazole ring.

A very simple annulation reaction was designed, allowing an imidazole moiety to be fused onto a range of pyridine-based derivatives. The methodology consists of an activation step via the formation of a pyridinium salt to increase the electrophilicity of the pyridine ring, followed by a cascade reaction triggered by a nucleophilic attack of the iminium moiety. Depending on the pyridinium salt, it is possible to obtain functionalized imidazole moieties.