Synthesis of Biscoumarins from 4-Hydroxycoumarin and Aromatic Aldehydes—A Comparative Assessment of Percentage Yield Under Thermal and Microwave-Assisted Conditions

A convenient synthesis of various biscoumarins by condensing a series of aldehydes with 4-hydroxycoumarin under microwave irradiation is reported for the first time along with a comparative account of the syntheses under conventional conditions. The reaction times have been reduced considerably with improvement in yields in comparison to thermal conditions. The reactions have been carried out in solvent as well as under solvent-free conditions, and the adopted procedure provides an energy-and time-saving protocol.