Ultrasound‐Assisted Pechmann Condensation of Phenols With β‐Ketoesters to Form Coumarins, in the Presence of Bismuth(III) Chloride Catalyst

Ultrasound was found to synergistically accelerate the condensation of phenol with β‐ketoesters in the presence of BiCl3. In the absence of ultrasound, under the same conditions, the reaction was found to be slow. Thus, the reaction can be carried out in the presence of ultrasound at room temperature (28–30°C), with a considerable reduction of reaction time, with high yield and high purity of coumarins.