Titanium dioxide nanoparticles (TiO2 NPs) were used as an effective catalyst in the solvent-free, one-pot threecomponent
reaction of aromatic aldehydes, malononitrile and 4-hydroxycoumarin to produce corresponding dihydropyrano[
c]chromenes in high yields. This method has the advantages of a simple operation, short reaction time, high yields,
easy work-up, reusability of the catalyst, and an environmentally friendly specificity.