Photochemistry in supercritical carbon dioxide. The benzophenone-mediated addition of aldehydes to α,β-unsaturated carbonyl compounds

The photo-induced addition of aldehydes to α,β-unsaturated carbonyl compounds is an effective, ‘environmentally benign’ method for the synthesis of 2-acyl-1,4-hydroquinones (from quinones) and 1,4-diketones (from enones). This process has been improved by eliminating benzene as a solvent and replacing it with supercritical carbon dioxide. Highest yields were obtained at higher CO2 pressures, or with the addition of 5% t-butyl alcohol as co-solvent.