Phenyl acetate photochemical rearrangement

The reaction is apparently intramolecular, since irradiation of phenyl Acetate in the presence of o-dihydroxybenzene gives no cross-products (186). A careful study of the photochemical rearrangements of esters of the type ArOCOCH3 has delineated the synthetic possibilities of the rearrangement (188). The photorearrangement proceeds under milder con-... 

Cyclodextrins form inclusion compounds in aqueous solution with various molecules which may then exhibit modified reactivity (see reference 185 above). It was reported in 1975 that the presence of p-cyclodextrin modified the ortho para ratio of hydroxyacetophenones formed photochemically from phenyl acetate,and the photoinduced rearrangements of acetanilide, ben-zanilide, and ethyl phenyl carbonate under similar conditions are now reported. In each case the para rearrangement isomer is favoured, and this is rationalized in terms of the aromatic nucleus being bonded into the cyclodextrin cavity such that the ortho and weta positions are shielded whDe the para position is accessible. This proposal is supported by observations that para but not ortho disubstituted arenes are well bonded into p-cyclodextrin cavities. The by-product formation of aniline from the amides and of phenol from the carbonate is also markedly reduced for reactions in the presence of the cyclodextrin. 

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. 

Photochemical Fries rearrangements. Photochemical rearrangement of phenyl acetate (1) gives the o-and p-hydroxy ketones (2) and (3) in equal amounts and phenol. When cyclodextrin is present, the rearrangement becomes... 

Ohara, M. and Watanabe, K., Selective photochemical Fries rearrangement of phenyl acetate in the presence of P-cyclodextrin, Angew. Chem. Int. Ed. Engl, 14, 820,1975. 

The discovery of a real photochemical homoallylic rearrangement of 2-aryl-cyclopropylcarbinyl acetates (32) and (33) has been reported.28 In cyclohexane the products formed [from (32a)] are the corresponding m-cyclopropane and the homoallyl product [(34), 25%] (minor amounts of benzylcyclohexane and 1-phenyl butadiene were also detected). Acetone sensitization shows that the... 

The rearrangements of aldehydes 31 and 32 demonstrated that the ODPM reactivity of P,y-unsaturated aldehydes is not restricted to phenyl-substituted compounds, but can also be extended to systems in which the intermediate biradicals are stabilized by conjugation with a vinyl group. Furthermore, the efficient synthesis of compounds 33 and 34 is of importance because it opens a novel photochemical route to chrysanthemic acid and other cyclopropyl components present in pyrethrins and pyrethroids. In fact, aldehyde 33 can be transformed to irans-chrysanthemic add by simple oxidation. This new s)mthetic route to ecologically benign insectiddes competes with the one previously described by us using the 1-ADPM rearrangement of P,y-unsaturated oxime acetates. ... 

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