Photo-Fries rearrangement lactone

Other ring contractions that give azapentalene derivatives include the rearrangement of a fused oxazine to a pyrazolo[l,5-a]indol-4-one with acetic anhydride,165 and an interesting photochemical contraction of a cyclic lactone, which produces an isomeric fused indolone by a mechanism thought to involve the first meta photo-Fries rearrangement [Eq. (19)].166 The product was used as an intermediate for the synthesis of mitomycin antibiotics (Section VI,A). 

The aryl succinates (94) undergo smooth photo-Fries rearrangements leading to the enol lactones (95). 

The photo-Fries rearrangement has been used in various synthetic reactions. A recent application concerned the synthesis of the mitomycin precursor (148) in high yield from the lactone (147). Finally, reference is made to the efficient photochemical deconjugation of piperidine esters (149) to the endocyclic isomers (150), presumably by a photoenolization reaction. ... 

Martmez-UtriUa, R. and Miranda, M. A., Indirect hydroquinone succinoylation via a photo-Fries rearrangement appUcation to the synthesis of enol lactones. Tetrahedron Lett., 21, 2281,1980. 

The mechanism of the photo-Fries reaction, both in the vapour and condensed phases, has been thoroughly established, and the many reported examples of the process with a wide variety of systems indicate the generality of the reaction.10 Although o- and p-migration products normally result from irradiation of aryl esters, structural constraints can lead to meto-rearrangement products, and the first useful meta-Fries reaction has now been described.188 Thus irradiation of the amino-lactone (147) in THF leads to 57% of the red crystalline isomer (148) via,... 

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See also in sourсe #XX -- [ , ]

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