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Paper | Regular issue | Vol 43, No. 2, 1996, pp.339-347
Published online, 1st January, 1970
DOI: 10.3987/COM-95-7262
Photolysis of 3-Bromochroman-4-ones

M. Consuelo Jiménez, Miguel A. Miranda*, and Rosa Tormos

*Departamento de Química/ Instituto de Tecnología Química, UPV-CSIC, Universidad Politécnica de Valencia, Apartado 22012, E-46071-Valencia, Spain

Abstract

Photolysis of 3-bromochroman-4-ones (1a-f) leads to debrominated chromanones (2a-f) and chromones (3a-f) as major products. Their formation is accounted for in terms of primary cleavage of the carbon halogen bond to give α-carbonyl radicals (I) and/or cations (II). In the case of the 2,2-disubstituted compounds (1d-f), intermediates (II) undergo rearrangement with 1,2-shift of the phenyl or benzyl substituent prior to deprotonation. Minor by-products are the pentacyclic pyrone (4e) or 2-methylchromone (3a) (starting from 1e and 1f, respectively).