Photo-Fries rearrangement cyclodextrins

The effect of complexation by j9-cyclodextrin on the photo-Fries rearrangement of benzene sulphanilide has been investigated. 

The photo-Fries rearrangement of phenyl acetate in aqueous solution in the presence and absence of B-cyclodextrin has been reexamined. In aqueous solution a mixture of phenol and the ortho and para isomers of hydroxyacetophenone is produced. When 3-cyclodextrin is present the quantum efficiency of formation of phenol and of the ortho product is increased. It is suggested that the enhanced photochemical yield of the ortho product reflects the less polar environment of the cyclodextrin cavity while the increased quantum yield of phenol formation reflects the availability of abstractable hydrogen within the cyclodextrin cavity. 

Also obtained by photo-Fries rearrangement of m-cresyl benzoate in ethanol for 24 h (25%) and in the presence of P-cyclodextrin (34%) [65]. 

Preparation by UV light irradiation of m-tolyl acetate, at r.t. (photo-Fries rearrangement) [2192], in ethanol (37%), with aqueous p-cyclodextrin solution (54%) or with p-cyclodextrin (soM) (95%). 

Syamala, M. S., Rao, B. N., and Ramamurthy, V., Modification of photochemical reactivity by cyclodextrin complexation product selectivity in photo-Fries rearrangement. Tetrahedron, 44, 7234,1988. 

Veglia, A. V. and de Rossi, R. H., Beta-cyclodextrin effects on the photo-Fries rearrangement of aromatic alkyl esters, /. Org. Chem., 58,4941, 1993. 

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