Diels-Alder reactions between maleic anhydride and furan derivatives in supercritical CO₂

A comparative analysis of the reactions between maleic anhydride and furan derivatives is presented in near and supercritical carbon dioxide and traditional organic solvents. Reaction kinetics were monitored by UV-vis absorbance spectroscopy in conjunction with an optimization technique which greatly simplified the experimental approach. In all of the reactions studied, supercritical carbon dioxide proved to facilitate a rate enhancement over conventional organic solvents. The reaction between maleic anhydride and furfuryl alcohol at 69 bar and 35°C was found to proceed 10 times faster in CO₂ compared to reactions carried out in diethyl ether. All kinetic results were obtained from reactions undertaken in true homogeneous one phase fluid systems. The results achieved further indicate the potential of using carbon dioxide as a medium to carry out such chemical transformations through more environmentally acceptable processes.