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Paper | Regular issue | Vol 24, No. 9, 1986, pp.2511-2517
Published online, 1st January, 1970
DOI: 10.3987/R-1986-09-2511
Photolysis of Cyclic Acetals of Aryl Benzoylacetates as the Key Step in a New Synthesis of Flavones

Hermenegildo García, Sara Iborra, Miguel A. Miranda,* and Jaime Primo

*Departamento de Química Orgánica, Universidad de Valencia, Calle Dr. Moliner, 50, E-46100 Burjassot (Valencia), Spain

Abstract

Although the yields found for the photo-Fries rearrangement of the aryl benzoylacetates 1 are poor, blocking of the carbonyl group, as in the related acetal derivatives 3, results in a substantial preparative improvement. Thus, the o-hydroxydibenzoylmethanes 2 are obtained from 1 with an average yield of 18%, while the corresponding acetals 4 are obtained from 3 with an average yield of 58%. Compounds 4 are efficiently converted into flavones 8 by means of wet silica gel, through hydrolysis of the acetal moiety and subsequent cyclization of the resulting o-hydroxydibenzoylmethanes 2.