Developments in Microwave-Assisted Organic Chemistry

TLDR

Microwave‑assisted organic chemistry is reviewed, noting that technical difficulties required specifically designed reactors. The study seeks to develop specifically designed reactors to overcome these technical difficulties. The authors introduced the CSIRO continuous microwave reactor (CMR) and microwave batch reactor (MBR), capable of rapid, controlled heating and cooling up to 200 °C/1400 kPa and 260 °C/10 MPa, respectively, eliminating wall effects and enabling concurrent and differential heating. The reactors were shown to optimize high‑temperature reactions such as the Willgerodt and Fischer indole syntheses, and water was demonstrated as a useful pseudo‑organic solvent for environmentally benign chemistry.

Abstract

Microwave-assisted organic chemistry is reviewed in the context of the methods employed. A range of technical difficulties indicated that specifically designed reactors were required. Hence, the CSIRO continuous microwave reactor (CMR) and microwave batch reactor (MBR) were developed for organic synthesis. On the laboratory scale, they operated at temperatures (pressures) up to 200°C (1400 kPa) and 260°C (10 MPa), respectively. Advantages and applications of the units are discussed, along with safety issues. Features include the capability for rapid, controlled heating and cooling of reaction mixtures, and elimination of wall effects. Concurrent heating and cooling, and differential heating were unique methodologies introduced to organic synthesis through the MBR. Applications of the microwave reactors for optimizing high-temperature preparations, e.g, the Willgerodt reaction and the Fischer indole synthesis, were demonstrated. Water was a useful pseudo-organic solvent, applicable to environmentally benign synthetic chemistry.