Photoisomerization of 4,5-dihydrooxepin

Cockroft, Robert D.; Waali, Edward E.; Rhoads, Sara Jane

doi:10.1016/s0040-4039(01)98522-3

Cited by 6 publications

(2 citation statements)

References 8 publications

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“…Several possible pathways for the transformation of 8b to 9b have at least partial precedent in the literature and are summarized in Scheme . A diradical mechanism was suggested as a possible pathway for the related photoisomerization of 4,5-dihydrooxepin to 2-cyclopentenecarbaldehyde via homolytic cleavage of a C−O bond, followed by radical recombination .…”

Section: Resultsmentioning

confidence: 99%

Rearrangements of the Diels−Alder Cycloadducts Obtained from Acetylenic Sulfones and 1,3-Diphenylisobenzofuran

2006

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1,3-Diphenylisobenzofuran afforded Diels-Alder cycloadducts 4a,b with n-butyl- and phenyl-substituted acetylenic sulfones 3a,b, respectively. The products underwent various types of rearrangements under pyrolytic, acid-catalyzed, and photochemical conditions. In the presence of acid, or upon heating in xylenes, they afforded the ketones 5a,b. In addition, the dehydration product 7a was produced from the pyrolysis of 4a, and the unexpected transposed ketone 6b was generated under acid-catalyzed or pyrolytic conditions from 4b via a postulated epoxide intermediate. The photolysis of 4a afforded ketone 5a as the sole isolated product, whereas 5b afforded oxepin 8b and indenyl phenyl ketone 9b. The formation of the latter two products can be rationalized by a series of pericyclic reactions. These include an intramolecular [2+2] cycloaddition, followed by a 1,3-dipolar cycloreversion, for the transformation of 4b to 8b and a series of electrocyclic and [1,3]sigmatropic reactions to convert 8b into 9b.

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Section: Resultsmentioning

confidence: 99%

Rearrangements of the Diels−Alder Cycloadducts Obtained from Acetylenic Sulfones and 1,3-Diphenylisobenzofuran

2006

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“…rearrangement with phenyl-vinyl bridging (path a Scheme 6) totally preferred over vinyl-vinyl bridging (path b, Scheme 6), it appears, at first glance, that it could be due to the localization of the excitation energy mostly in the phenyl groups. Indeed, the divinyl ether chromophore (in a seven-membered ring) absorbs at 216 nm (E 3720) and 231 nm (E 2000) (27) while phenyl absorbs at 255 nm (E 204) (28). However, it would be very surprising if both SCHEME 6.…”

Section: Although Sensitization and Quenching Resultsmentioning

confidence: 99%

Synthesis and photochemistry of 4,4-diphenyl- γ-pyran. Di-π-methane rearrangement in a new chromophore

Gravel¹,

Leboeuf²,

Caron³

1977

Can. J. Chem.

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A synthesis of 4,4-diphenyl-γ-pyran (1) was elaborated from diphenylmethane. Prolonged irradiation of pyran 1 in tert-butyl alcohol led to: trans-endo-5,6-diphenyl-2-oxabicyclo[3.1.0]-hexene (18), isomeric 3,5-diphenylpenta-2,4-dienals (6), trans-tert-butyl 3,5-diphenylpent-2-enoate (7), cis-tert-butyl 3,5-diphenylpent-2-enoate (8), and isomeric 3,5-diphenylpent-2-enoic acids (9). It was established that the photolysis of γ-pyran 1 yields only one primary photoproduct: the oxabicyclo[3.1.0]hexene derivative 18 via a di-π-methane rearrangement. The other compounds isolated result from further irradiation of the primary product. The results observed are discussed in the light of the di-π-methane rearrangement mechanism.

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