Transition Metal-Catalyzed Organic Reactions in Supercritical Carbon Dioxide

This paper reviews recent progresses of the organic reactions catalyzed by transition metals in supercritical carbon dioxide (scCO2) in our group. The reactions include oxidation, reduction, carbonylation, radical addition, C-C coupling and cycloaddition reactions. All the reactions can be performed in scCO2 with equal or even better results than in conventional organic solvents, owing to the high diffusion and low viscosity of scCO2. The addition of suitable amount of co-solvents in scCO2 is necessary in most reactions, because it not only improves the solubility of transition metal salts in scCO2, but also regulates the ratio of products and raises the selectivity as well. Our work demonstrates that scCO2 and its modifier can be used as an alternative solvent for toxic organic solvents, and thus offers an environmentally friendly medium for the development of new synthetic methods in green organic chemistry.