A simple and green method for the synthesis of 1,5-dihydropyrano[2,3-c]chromene derivatives
has been reported by three-component reaction of aromatic aldehydes, malononitrile, and
3-hydroxycoumarin in the presence of a series of novel crown ether-based ionic liquids (CE-based ILs)
in H2O/EtOH (1:1), under the reflux conditions. The novel CE-based ILs have been synthesized by
18-crown-6 or dibenzo 18-crown-6 chelated with sodium benzenesulfinate derivatives and used as a green
and environmental organocatalyst. This method has some advantages such as the aqueous reaction medium,
stable catalysts, cleaner reaction profiles and high yield of products in short reaction time.