Abstract
High-pressure and high-temperature water including supercritical water with its unique properties is considered as a green solvent; a suitable replacement of conventional organic solvents. Until to the date, there were little successful examples to conduct organic reactions using high-pressure and high-temperature (HPHT) water in batch-wise method. Recently, we developed a high-pressure and high-temperature water microreaction system, which can be successfully used to conduct various organic reactions, resulted high yield and high selectivity of desired products within a very short reaction time. For instance, Claisen rearrangement can be achieved with almost quantitative yields within a few minutes in the absence of catalysts as well as any organic solvents at the reaction temperature and pressure of 250°C and 5 MPa, respectively. Furthermore, the microreaction system was also effective for palladium catalyzed cross coupling (Sonogashira coupling) and obtained almost 100% yields within the shortest reaction time of 0.1 s. The described system was advantageous in terms of the separation and purification of products due to the automatic separation of products from water. Successful application of the described microreaction system for various organic reactions without using any organic solvent make it a potential contender to the development of greener process not only in the small scale laboratory level but also will be extended to the industrial large scale production processes.
