The ultrasound promoted Knoevenagel condensation of aromatic aldehydes

Application of ultrasound has been found to greatly assist the Knoevenagel aldol condensation reaction of activated methylenes with aromatic aldehydes under mild conditions. The outcome of the ultrasound-promoted reaction depends upon the electronic nature of the armoatic aldehyde, the solvent employed and the addition of acids, bases or ammonium salts.