Solvent-Free Synthesis of 4,5-Dihydropyrano[c]chromene Derivatives Over TiO2 Nanoparticles as an Economical and Efficient Catalyst

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.