- Photolysis of 3-bromochroman-4-ones
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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).
- Consuelo Jiménez,Miranda, Miguel A.,Tormos, Rosa
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p. 339 - 347
(2007/10/03)
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- Influence of the β-Substitution on the Photochemistry of α,2-Diacetoxystyrenes. Irradiatin of Phenyl, Vinyl, and Benzyl Derivatives
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β-Substitution shows a pronounced influence on the photochemistry of α,2-diacetoxystyrenes.As in the case of the parent compound, intramolecular cyclization with participation of the neighbouring 2-acetoxy group takes place upon irradiation of the enol esters 4a-c; however other processes are also observed, depending on the substrate.The phenyl derivative 4a gives the E isomer 7a and the phenanthrene 9.The vinyl derivative 4b also undergoes cis-trans isomerization and/or photooxidation, to afford 7b and 10.Finally, a 1,4-acyl migratin occurs in the benzyl derivative 4c, whereby the 1,4-diketone 12 is formed.
- Alvaro, Mercedes,Baldovi, Vicenta,Garcia, Hermenegildo,Miranda, Miguel, A.,Primo, Jaime
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p. 267 - 274
(2007/10/02)
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- A NOVEL PHOTOCHEMICAL 1,4-ACYL MIGRATION IN ENOL ESTERS. THE PHOTOLYSIS OF ENOL ACETATES OF 3-PHENYLPROPIOPHENONES
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Photolysis of the enol acetates 1a, b gives the 1,4-diketones 4a, b by a mechanism involving a primary homolytic carbonyl-oxygen bond cleavage, followed by 1,2-hydrogen shift and in cage recombination.
- Alvaro, M.,Baldovi, V.,Garcia, H.,Miranda, M. A.,Primo, J.
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p. 3613 - 3614
(2007/10/02)
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