Efficient one-pot catalyst-free synthesis of novel coumarin- spiro[indoline-3,4'-pyran] conjugates via three-component domino reaction in aqueous medium

A simple, efficient, eco-friendly and catalyst-free procedure was developed for the construction of novel coumarin-spiro[indoline-3,4'-pyran] conjugates via three-component reactions of various synthetic beta-ketoesters with isatins and malononitrile in aqueous medium. In addition to operational simplicity and absence of tedious separation procedures, being catalyst–free is the prominent advantage of this method.