Pushing Photochemistry into Water: Acceleration of the Di-π-Methane Rearrangement and the Paternó-Büchi Reaction “On-Water”

Abstract

Two representative organic photoreactions, namely a bimolecular photocycloaddition and a monomolecular photorearrangement, are presented that are accelerated when the reaction is performed “on-water”, that is, at the water-substrate interface with no solvation of the reaction components. According to the established models of ground-state reactions “on-water”, the enhanced efficiency of the photoreactions is explained by hydrophobic effects (Paternó-Büchi reaction) or specific hydrogen bonding (di-π-methane rearrangement) at the water-substrate interface that decrease the energy of the respective transition state. These results point to the potential of this approach to conduct photoreactions more efficiently in an ecologically favorable medium.