Use of Ultrasound in the Synthesis of Heterocycles of Medicinal Interest

Abstract

In the last decade, sonochemistry has become an interesting field of research in both organic chemistry and pharmaceutical industry. It is well known that the sonochemical effects are derived from a phenomenon known as acoustic cavitation, i.e., the formation, growth, and implosion of microbubbles inside a liquid. These effects induce high temperatures (near 5000 K) and very high pressures (around 1000 atm) inside such cavities, while shock waves at the interface and bulk liquids are largely responsible for enhanced mass and energy transfers. By virtue of such effects as mentioned above, ultrasound-assisted organic synthesis constitutes a convenient way to accelerate and improve the synthesis of a great number of heterocyclic compounds with analgesic, antipyretic, anti-inflammatory, antibacterial, and fungicidal properties. Moreover, it is important to mention that other heterocyclic compounds have been used in cancer treatment, cardiovascular disease, type 2 diabetes, migraine, and anxiety; also can be used as anticonvulsants, sedatives, and hypnotic agents. Due to the wide range of heterocycles synthesis, the reaction conditions may be quite different, such as temperatures, aqueous or organic solvents, ionic liquids, or catalysts in solvent-free reactions. So, it is very important to carry out an exhaustive study of these variables in order to obtain the best yield.