Synthetic methodologies using Sonincation techniques

Ultrasound generates cavitation, which is "the formation, growth, and implosive collapse of bubbles in a liquid. Cavitation collapse produces intense local heating (~5000 K), high pressures (~1000 atm), and enormous heating and cooling rates (>109 K/sec)" and liquid jet streams (~400 km/h), which can be used as a source of energy for a wide range of chemical processes. This review will concentrate on theory, reactions and synthetic applications of ultrasound in both homogeneous liquids and in liquid-solid systems. Some recent applications of ultrasound in organic synthesis, such as, Suzuki reaction, Sonogashira reaction, Biginelli reaction, Ullmann coupling reaction, Knoevenagel condensation, Claisen-Schmidt condensation, Reformatsky reaction, Bouveault reaction, Baylis-Hillman reaction, Michael addition, Curtius rearrangement, Diels-Alder reaction, Friedal-Craft acylation, Heck reaction, Mannich type reaction, Pechmann condensation and effect of ultrasound on phase transfer catalysis, oxidationreduction reactions, ionic liquids and photochemistry are reviewed. Ultrasound found to provide an alternative to traditional techniques by means of enhancing the rate, yield and selectivity to the reactions.