A very simple, efficient solvent-free, and catalytic method for the synthesis of coumarins is described, especially ZnO nanoparticles has been used as a recyclable catalyst for Knoevenagel condensation reactions. Zinc oxide shows better activity in many organic reactions. These high relativities are due to high surface areas combined with unusually reactive morphologies. In this paper ZnO nanoparticle by varying the surfactants at particular PH =1 and heat treatment at 5000C by using muffle furnance. The prepared agglomerated and non-agglomerated ZnO nanoparticles is used to analyse the rapid synthesis of Simple and efficient solvent-free method for the synthesis of coumarins is described. Knoevenagel condensation of various o-hydroxy benzaldehyde with 1,3-dicarbonyl compounds in the presence of catalytic amount of zinc oxide (ZnO) nanoparticles under microwave and thermal conditions affords the products. The advantages of M.W method are high yields, short reaction times, low cost and matching with green chemistry protocols.
