Efficient utilization of supercritical carbon dioxide as both reactant and reaction medium for synthetic applications

Abstract

Carbon dioxide is an attractive C1 building block in organic synthesis. However, due to the inert nature of CO2, its activation and incorporation into organic substrates still remain a significant synthetic challenge. Accordingly, special methodologies (catalysts and/or reaction media) have been developed for CO2 activation. Supercritical CO2 is considered to offer advantages as a reaction medium and a substrate because of its unique physicochemical properties, such as high gaseous miscibility, efficient mass transfer due to enhanced diffusivity, easily tunable properties with variation of pressure or temperature, and disappearance of the gas-liquid phase boundary peculiar to the supercritical state. In addition, CO2, which is nontoxic and has an easily accessible critical point, can replace hazardous organic solvents. Moreover, by utilizing supercritical CO2 we can simplify the separation process. This chapter first provides an introduction to the supercritical fluids. Some of the applications of supercritical CO2 both as a reactant and as a green reaction medium in synthesis of heterocyclic compounds such as cyclic carbonates, oxazolidinones, quinazolines, etc. are exemplified and discussed in the next sections.