Three-component, One-pot Synthesis of Dihydropyrano[3,2-c]chromenes in Aqueous Medium in the Presence of Nano-silica Supported 1,5-Diazabicyclo(4.3.0)non-5-en

In this research, a high efficient, simply and rapid method was applied for the synthesis of dihydropyrano[3,2-c]chromene derivatives by one-pot, three-component condensation of aldehydes, malononitrile and 4-hydroxycoumarin in H2O/ethanol (1:1 v/v) under reflux conditions. This reaction was run by using nano-silica supported 1,5-Diazabicyclo(4.3.0)non-5-en (DBN) which has been abbreviated as nano-SiO2/DBN under aqueous condition. The nano-SiO2/DBN catalyst was synthesized by reaction between silica chloride and DBN. The main advantages of this procedure are high yields, short reaction times and easy work-up. Furthermore, the catalyst could be reused for five times.