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

<p>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-<i>a</i>]pyridine-2-carbaldehyde <b>1</b> and malononitrile resulted in the formation of starting material <b>2</b>. Subsequently, intramolecular cyclization between the cyano group of <b>2</b> and acetophenones, naphtols, hydroxyquinolines, or phenols, gave <b>3</b>, <b>4</b>, <b>5,</b> and <b>6</b> 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.</p>