Photocycloaddition of 4,4-Dimethylcyclohexenone to 1,1-Diphenylethylene. Evidence for a Triplet Exciplex Intermediate

Caldwell, Richard A.; Hrncir, Duane C.; Muñoz, T.; Unett, D. J.

doi:10.1021/ja9606891

Cited by 17 publications

(16 citation statements)

References 38 publications

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“…For a,b-unsaturated carbonyl compounds the [2+2]-photocycloaddition proceeds in a different manner as their S 1 state is of the np*-type. 12 Subsequent intersystem crossing (ISC) is fast and the cyclobutane formation occurs from the triplet state (T 1 ) via 1,4-biradical intermediates 13,14 (Scheme 1, path B). As the np*-excitation is sufficient to initiate a successful photocycloaddition a Pyrex or Duran glass apparatus may be used which cuts off irradiation below l ≤ 300 nm.…”

Section: Methodsmentioning

confidence: 99%

Stereoselective Intermolecular [2 + 2]-Photocycloaddition Reactions and Their Application in Synthesis

Bach

1998

Synthesis

295

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Stereoselective intermolecular [2+2]-photocycloaddition reactions of alkenes and Paternò-Büchi reactions are reviewed. For both reactions the regioselectivity and the simple diastereoselectivity which are relevant to the formation of a single product isomer are explained based on representative examples. In the subsequent sections the facial diastereoselectivity induced by the respective reaction partner is treated. Particular emphasis is given on synthetic applications of the cyclobutanes and oxetanes obtained by the photochemical key step. Consecutive reactions are discussed and the potential use of the four-membered ring intermediates is highlighted.

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Section: Methodsmentioning

confidence: 99%

Stereoselective Intermolecular [2 + 2]-Photocycloaddition Reactions and Their Application in Synthesis

Bach

1998

Synthesis

295

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“…The enone-ene cycloadditions proceeds via a triplet exciplex as shown by Caldwell and co-workers for the 4,4dimethylcyclohexenone/1,1-diphenylethene system. 54 This intermediate has a remarkably long lifetime of approximately 50 ns and might be formed in competition with or prior to the triplet 1,4-biradical. These tetramethylene biradicals have comparable lifetimes of 50-100 ns 4, 12,55 and can be intercepted with radical traps.…”

Section: The Enone-ene Photocycloadditionmentioning

confidence: 99%

Spin‐Selectivity in Photochemistry: A Tool for Organic Synthesis

Griesbeck¹

2003

ChemInform

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“…Evidence for a triplet exciplex intermediate has been proposed in the photocycloaddition reaction of 4,4dimethylcyclopentenone to 1,1-diphenylethylene. 30 Whether the present species is an exciplex or biradicals will require different kinds of experimentation.…”

Section: Flash Photolysis Studiesmentioning

confidence: 99%

Photochemistry of substituted cyclic enones. Part 12.1 Photocycloaddition of 3-phenylcyclopentenone and 3-phenylcyclohexenone to (E )- and (Z )-1-phenylpropene

Kelly¹,

Kelly²,

McMurry³

1999

J. Chem. Soc., Perkin Trans. 2

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The quantum yields of adduct formation and isomerisation of (E)-and (Z)-1-phenylpropene by 3-phenylcyclopentenone 1 and 3-phenylcyclohexenone 2 have been measured by 1 H-NMR spectroscopy in solutions of d 6 -benzene. The adducts formed for each photoreaction have been shown to be independent of the starting 1-phenylpropene isomer. For 3-phenylcyclopentenone 1, a photostationary state of 32 : 68 (E)-to (Z)-1-phenylpropene is achieved during the course of the reaction. This isomerisation reaction may occur through reversion of triplet 1,4-biradical intermediates to ground state molecules or by an energy transfer process. However for 3-phenylcyclohexenone 2 isomerisation occurs only through reversion of triplet 1,4-biradical intermediates. The mechanism of photoadduct formation and that of the isomerisation reaction are discussed for both phenylenones.Rate constants for quenching of the 3-phenylcyclopentenone 1 and 3-phenylcyclohexenone 2 triplet states by (E)-and (Z)-1-phenylpropene, 3 and 4, in cyclohexane and benzene solutions have been recorded using laser flash photolysis. In cyclohexane at high quencher concentration, complex decay kinetics are observed consistent with observation of both the enone triplet state and either a triplet exciplex or 1,4-biradical intermediates.

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Photocycloaddition of 4,4-Dimethylcyclohexenone to 1,1-Diphenylethylene. Evidence for a Triplet Exciplex Intermediate

Cited by 17 publications

References 38 publications

Stereoselective Intermolecular [2 + 2]-Photocycloaddition Reactions and Their Application in Synthesis

Stereoselective Intermolecular [2 + 2]-Photocycloaddition Reactions and Their Application in Synthesis

Spin‐Selectivity in Photochemistry: A Tool for Organic Synthesis

Photochemistry of substituted cyclic enones. Part 12.1 Photocycloaddition of 3-phenylcyclopentenone and 3-phenylcyclohexenone to (E )- and (Z )-1-phenylpropene

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