Change of Selectivity in the Photo-Fries Rearrangement of Phenyl Acetate Induced by β-Cyclodextrin

Article abstract of DOI:10.1021/jo00300a025

The photolysis of phenyl acetate (1) in water and in solutions containing β-cyclodextrin (CD) leads to p-hydroxyacetophenone (2), o-hydroxyacetophenone (3), and phenol (4).There is a decrease in the total amount of rearrangement products when the reactions are carried out in the presence of oxygen, but the inhibition is less marked in the presence of CD.The <3>/<2> and <4>/(<3> + <2>) ratios increase from 2.4 to 3.7 and from 0.21 to 0.76 respectively when the CD concentration changes from 0 to 10 mM.These changes are due to the increase in the quantum yield for theformation of 3 and 4 in solutions containing CD.Under the conditions of this study, the substrate reacted in the bulk solution and in the cavity of CD.The quantum yields for the formation of 3 and 4, Φ_CD³ and Φ_CD⁴, are higher for the included substrate than the corresponding values for the free substrate.This effect is attributed to the fact that the reaction is taking place in a less polar microenvironment.Besides, Φ_CD⁴ also increases due to the availability of hydrogens bonded to secondary carbons in the cavity of cyclodextrin.