Titanium dioxide nanoparticles as efficient catalyst for the synthesis of pyran’s annulated heterocyclic systems via three-component reaction

Titanium dioxide nanoparticles were introduced as a new and efficient heterogeneous catalyst for the synthesis of pyran’s annulated heterocyclic systems via three-component reaction. The reaction was carried out between various aldehydes, malononitrile, and cyclic CH-acids in H2O as a green solvent at 50 °C during 10 h. This reaction gave pyrans containing heterocyclic compounds including nineteen derivatives in good yields. Titanium dioxide nanoparticles were recycled and reused for six times without significant decrease in the catalyst amount and efficiency. This approach is very efficient, economical, and environmentally benign process since titanium dioxide is a cheap, available, non-toxic, and recyclable catalyst.