A highly efficient, rapid one-pot synthesis of some new heteroaryl pyrano[2,3-c]pyrazoles in ionic liquid under microwave-irradiation

Abstract

A highly efficient, rapid one-pot procedure has been developed for a three-component domino intermolecular Knoevenagel–intermolecular hetero-Diels–Alder reaction, to afforded indolyl- and quinolylpyrano[2,3-c]pyrazoles from corresponding heteroarylaldehyde, pyrazolone and enol ether in ionic liquid triethylammonium acetate (TEAA) under microwave (MW) irradiation. The reaction advantageously precedes in highly regio- and stereoselective manners in combination with the ease of recovering ionic liquid used in the reaction. According to literature, the heterocycles are expected to display antitubercular activity. 2D NMR NOESY (nuclear overhauser effect spectroscopy) experiments confirm the cis-orientation of the two pyran ring hydrogens; one attached to the anomeric carbon and the second to which a heteroaryl attached.