Simple synthesis of imidazo[1,2-A]pyridine derivatives bearing 2-aminonicotinonitrile or 2-aminochromene moiety

A simple and general method for the synthesis of new imidazopyridines bearing an aminopyridinyl, chromenyl, or quinolinyl moiety in the C2 position was developed. The Knoevenagel reaction between imidazo[1,2-a]pyridine-2-carbaldehyde 1 and malononitrile resulted in the formation of starting material 2. Subsequently, intramolecular cyclization between the cyano group of 2 and acetophenones, naphtols, hydroxyquinolines, or phenols, gave 3, 4, 5, and 6 compounds, respectively. This is a simple, reproducible, and environmentally friendly method of synthesizing substituted imidazopyridines using water as a solvent or under solvent-free conditions.