Directed Solid-Phase Synthesis of Trisubstituted Imidazo[4,5‑c]pyridines and Imidazo[4,5‑b]pyridines

An efficient method is described for the solid-supported synthesis of imidazo­[4,5‑b]pyridines and imidazo­[4,5‑c]pyridines from 2,4-dichloro-3-nitro­pyridine. The key pyridine building block was reacted with polymer-supported amines, followed by replacement of the second chlorine with amines, nitro group reduction, and imid­azole ring closure with aldehydes. Depending on the combination of polymer-supported and solution-phase reagents, the strategy allowed for the simple preparation of the target trisubstituted derivatives with variable positioning of the pyridine nitrogen atom. Additionally, after a slight modification of the method, the preparation of strictly isomeric imidazo­pyridines was possible.