Solvent-free synthesis of biologically active spiro-4H-pyran derivatives promoted by calcium oxide nanoparticles as an environmentally benign nature catalyst

Simple and economical procedure for the synthesis of biologically active spiro-4H-pyran derivatives has been found through the three-component, one-pot condensation of isatin, malononitrile and different reagents including 1, 3-dicrbonyl compounds, naphthol and 4-hydroxycumarin under thermal and solvent-free conditions in the presence of calcium oxide nanoparticles as an efficient catalyst. The major advantages of this present methodology are milder reaction conditions, eco-friendly, environmentally benign, non-toxic and inexpensive catalyst, experimentally simplicity, high yields and short reaction times.