SnO2 nanoparticles: A recyclable and heterogeneous catalyst for Pechmann condensation of coumarins and Knoevenagel condensation-Michael addition of biscoumarins.

Recyclable SnO2 nanoparticles catalyze the Pechmann condensation between phenolic alcohols and ß-ketoesters at room temperature in ethanol leading to coumarins. Also, in another study the synthesis of biscoumarins catalyzed by SnO2 nanoparticles in the reaction between 4-hydroxycoumarin and aldehydes under same condition reactions. The corresponding coumarins and biscoumarins were produced efficiently with facility and excellent yields (93-98%). These approaches display the advantages of benign reaction conditions, non-chromatographic purification procedure, appropriate functional group tolerance and valuable process.