CHANGE OF SELECTIVITY IN THE PHOTO-FRIES REARRANGEMENT OF PHENYL ACETATE INDUCED BY BETA-CYCLODEXTRIN

The photolysis of phenyl acetate (1) in water and in solutions containing (3-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 O.21 to O.76 respectively when the CD concentration changes from 0 to 10 mM. These changes are due to the increase in the quantum yield for the formation 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, $CD3and $CD 4, 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, 4>cd 4also increases due to the availability of hydrogens bonded to secondary carbons in the cavity of cyclodextrin. © 1990, American Chemical Society. All rights reserved.