Ultrasound-Promoted Regioselective Synthesis of Pyrazolyl-Bis Coumarinyl Methanes Using Citric Acid as a Natural and Efficient Catalyst.

This study reports a clean and environmentally benign route for the synthesis of a series of pyrazolyl-bis coumarinyl methane derivatives by a nucleophilic addition reaction of synthetized pyrazolecarbaldehyde and two equivalents of 4-hydroxycoumarin, using a catalytic amount of citric acid as a one-pot and green reaction under ultrasound irradiation at room temperature. The present methodology offers several advantages, such as green media, mild conditions, excellent yields, a simple procedure, and reduced environmental consequences. The structures of the synthesized pyrazolyl-bis coumarinyl methane compounds were confirmed by 1H, 13C NMR and FTIR spectral data and elemental analyses. [ABSTRACT FROM AUTHOR]