ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The 2, 5-diene-1, 7-dione 12 rearranges photochemically to the cyclopentenonyl-cyclopropyl ketone 13. Dienone 12 does not emit phosphorescence at 78K. Sensitization and quenching experiments indicate that the photorearrangement occurs in an excited triplet state with ET between ca. 61-65 kcal/mol according to sensitization data, and between ca. 54-58 kcal/mol according to quenching results. By comparison, the 2, 5-dienone 1 behaves similarly with respect to sensitization and quenching of its photorearrangement [3] (indicating ET 〈 61 and ca. 54-58 kcal/mol, respectively) and to its lack of phosphorescence, while the 2-ene-1, 5-dione 8 emits phosphorescence (ET = 72.4 kcal/mol) and sensitization, and quenching data indicate ET between ca. 68-72 and 〉61 kcal/mol for its photorearrangement, respectively. It is concluded that the triplet energy of the reactive state of compound 12 extends either over the two enone groups involving strong interaction or is localized on the ring A enone only.Photoproduct 13 rearranges further to the stereoisomer 14 on direct excitation and sensitization with acetophenone. Thioxanthone as triplet sensitizer and naphthalene as triplet quencher are ineffective. The reverse isomerization process, i.e. 14 → 13, is not observed.
Additional Material:
1 Tab.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19700530725
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