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Paper | Regular issue | Vol 27, No. 3, 1988, pp.673-681
Published online, 1st January, 1970
DOI: 10.3987/COM-87-4244
Studies on the Synthesis of Preconcenes. The Photo-Fries Rearrangement of Ester of α,β-Unsaturated Carboxylic Acid and meta-Oxygenated Phenols

Miguel A. Miranda,* Jaime Primo, and Rosa Tormos

*Departamento de Química Oránica, Facultad de Farmacia, Av. Blasco Ibañez 13, 46010 Valencia, Spain

Abstract

The photo-Fries rearrangement of a series of aryl esters of α β-unsaturated carboxylic acids 1a,b and 2 has been investigated, in order to explore the possibilities of this reaction as a key step in the synthesis of precocenes and related compounds. In all cases, the photolysis in hexane does not lead to any observable transformation, but in the presence of potassium carbonate takes place a migration of the acyl group to the two ortho-positions. Additionally, trans-cis photoisomerization occurs with the trans-butenoate 1b. The resulting-o- hydroxyketones 4a,: 4b, 4c, 5a , 5b , 5c, and 8 are easily and efficiently cyclized to the corresponding 4-chromanones 6a, 6b, 7a, 7b, and 9. A second photo-rearrangement is observed in the case of 9, although the yield is low, due to deactivation by the carbonyl group. Cyclizatlon of 10 gives rise to the tricyclic dichromanone 11. Compounds 6a and 11 are reduced and subsequently dehydrated by known procedures to afford the active chromenes 3 and 12.