Modification of photochemical reactivity by cyclodextrin complexalion: product selectivity in photo-fries rearrangement

Abstract

Cyclodextrin encapsulation, both in the solid state and in aqueous solution brings about a remarkable regulation of the photo-Fries rearrangement of phenyl esters and anilides. In comparison to the nonselective mixture of ortho and para-rearranged isomers along with the deacylated product obtained in organic solvents, the solid β-cyclodextrin complexes of unsubstituted esters and anilides show a remarkable 'ortho-selectivity'. An impressive regio-selectivity' among the two ortho-rearranged isomers is observed for meta-substituted esters and anilides upon irradiation as β-cyclodextrin complexes. Specific orientations of the unsubstituted and meta-substituted esters and anilides in the β-cyclodextrin cavity are suggested to be responsible for the observed selectivity.