Microwaves, Power Ultrasound, and Ionic Liquids. A New Synergy in Green Organic Synthesis

Although the vast majority of organic chemists still cling to conductive heating as a means to promote reactions, major advances have recently been made in this connection. Both dielectric microwave heating (MW) and power ultrasound (US) are being increasingly exploited in organic synthesis, and their combined use is one of the most promising innovations. A long way from pioneering approaches, when domestic MW ovens and US cleaning baths were poorly standardized tools, these techniques now appear in reproducible, high-yield synthetic protocols. Their important contributions towards developing environment-friendly procedures overlap the application domain of room-temperature ionic liquids (RTILs). The synthesis itself of these highly versatile green solvents can be efficiently promoted under US and/or MW irradiation. This review focuses on the advantages arising from the use of these energy sources and their combination with unconventional reaction media such as RTILs. The synergies arising from the combined use of US, MW and RTIL will certainly go a long way to meet the increasing demand for environmentally benign chemical processes.