Chemistry of cycloheptadienones.  VII.  Direct evidence for an ionic intermediate in the photoisomerization of eucarvone in acidic media

Hine, K. E.; Childs, Ronald F.

doi:10.1021/ja00799a048

Cited by 6 publications

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“…The profound effect of protonation on the photoisomerizations of eucarvone has largely been attributed to the reversal in the relative energies of the n,n* and n,n* states attendant upon protonation (1,6). The uv spectra of l.BX3 and 1H are very similar (7) and it is again likely that the lowest energy transition in 1.BX3 is of n,n* character.…”

Section: Discussionmentioning

confidence: 99%

“…In preceding papers we have examined the interrelationship of the photochemistry of neutral and protonated ketones (1)(2)(3). It is apparent from these and related studies (4)(5)(6) that protonation represents a method of exerting considerable control over the excited states reached and products obtained in the photoisomerization of a carbonyl compound.…”

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confidence: 99%

“…However, it would appear that no systematic study of their behaviour has been made. To this end we have examined the photoisomerizations of the boron trihalide adducts of eucarvone, 1, a ketone for which the effects of protonation have been previously investigated (1). The boron halide complexes were selected for this study on the basis of their ready availability, ease of manipulation, and solubility characteristics as well as Can.…”

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Photoisomerization of the boron trihalide complexes of eucarvone

Childs¹,

Hor²

1977

Can. J. Chem.

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The photoisomerization of the BF3, BCl3 and BBr3 complexes of eucarvone (2,6,6-trimethylcyclohepta-2,4-dienone), 1, have been examined. Irradiation of these zwitterions at low temperature gave, after subsequent recovery of decomplexed materials, 3,7,7-trimethylbicyclo-[4.1.0]hept-2-en-4-one, 2, 2-methyl-5-isopropylphenol, 3, 2-methyl-6-isopropylphenol, 4, dehydrocamphor, 5, and carvone, 6. In the case of 1•BF3 and 1•BCl3 the initial photoproducts were shown to be the complexes of 2, 3, 4, and 5. The complexes of 6 were shown to arise from a secondary photoisomerization of 2•BX3. It was not possible to establish the primary product distribution, obtained from 1•BBr3 as further photoisomerization of 2•BBr3 occurred even at very low degrees of conversion. The mechanisms and synthetic utility of these reactions is discussed.

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Section: Discussionmentioning

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