A superior synthesis of diaryl ethers by the use of ultrasound in the Ullmann reaction

The use of ultrasound in the reactions of phenols with bromoarenes, in the presence of potassium carbonate and copper(I) iodide but without added solvent, gives better yields of diaryl ethers(typically 70–90%), at lower temperature (140 °C) than is customary for traditional Ullmann reactions; the role of ultrasound is primarily to break up the particles of the inorganic solids