Greener One Pot Synthesis of 2-Amino-4-arylquinoline-3-carbonitriles in Neat Water Under Microwaves

A general and efficient protocol is described for one pot three component intramolecular cyclization of anilines, aldehydes and malononitrile in neat water within very shorter reaction times and higher yield. Titled compounds synthesized under both microwave irradiation and classical heating for comparison purposes. The catalytic activity of L-proline in these reactions was tested over a set of aldehydes and amines, demonstrating that it is reactive toward a variety of functionalities. The role of water in reaction mechanism also demonstrated. The use of a monomode oven allowed an accurate consideration of the temperature distribution in the microwave reaction vessel, which revealed a very strong and unexpected thermal heterogeneity.