<i>trans</i>-2-Cyclooctenone

Eaton, Philip E.; Lin, Kang

doi:10.1021/ja01064a049

Cited by 65 publications

(27 citation statements)

References 2 publications

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“…Obviously, 22 dimerises via bis(allylic) 1,4-diradicals analogous to 14 and 15. [34,35] The thermal [2ϩ2] cyclodimerisation of (E)-2-cyclooctenone, [70] by contrast, affords an entirely different dimer distribution equally encompassing head-to-head and head-to-tail dimers. [71] …”

Section: The Thermal [2؉2] Cyclodimerisation Of (2e4z)-24-cyclooctamentioning

confidence: 99%

“…The molecular structure of diketone Scheme 11 23 is firmly established. [69] Diketone 27 was obtained by thermal dimerisation of trans-cycloct-2-en-1-one; [70,71] its molecular structure has been established by X-ray crystallography. [72] The molecular structures of the nitroxyl 2:2 adducts (Scheme 5) have been established by four lines of evidence:…”

Section: Elucidation Of Molecular Structures ؊ Synthetic Aspectsmentioning

confidence: 99%

“…8Ϫ10°C, 95% pure, containing 3. 6ar,6bt,12ac,12bc-1,2,3,4,6a,6b,9,10,11,12,12a,12b (27): This compound was formed (10%) together with regio-and stereoisomers in the course of the thermal dimerisation of (E)-cyclooct-2-en-1one [70,71] in heptane at 25°C and was isolated by preparative HPLC, m.p. 91Ϫ93°C.…”

Section: Cyclobuta[12][8]annulene (16) (A) By Thermolysis Of 12mentioning

confidence: 99%

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The Thermal [2+2] Cyclodimerisation of (E,Z)-Cycloocta-1,3-diene Revisited − Chemical Trapping and Properties of the Intermediate 1,4-Diradicals

et al. 2002

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Keywords: Cycloaddition / Radicals / Reaction mechanisms / ThermochemistryThe thermal [2+2] cyclodimerisation of (E,Z)-cycloocta-1,3diene (9), which is known to afford the cyclobutane dimers 11, 12, and 13, has been investigated in the presence of the nitroxyls 17 and 18 and of atmospheric dioxygen, all of which are known to be efficient trapping agents for carbon-centred free radicals. The nitroxyls have been found to divert the reaction from formation of the dimers to formation of 2:2 adducts of two molecules of 9 and two molecules of nitroxyl. The rate constant for the formation of the overall sum of the dimers plus the 2:2 adducts in the presence of nitroxyl has been found to equal the rate constant for the formation of dimers in the absence of nitroxyl. This and the molecular structures of the 2:2 adducts prove that two molecules of 9 combine irreversibly to produce the two epimeric bis(allylic) 1,4-diradicals 14 and 15 (meso and rac, respectively) which undergo two competing reactions: ring-closure to dimers 11, 12, and 13, and trapping by nitroxyl to form the 2:2 adducts. Dioxygen, too, was found to trap 14 and 15 efficiently. From the kinetics of the latter trapping reaction, studied at six temperatures between 5 and 55°C, the heights of the activation barriers separating 14 from 11 and 15 from 12 + 13 were estimated at 11.1 ± 1.5 and 10.2 ± 1.5 kcal·mol −1 , respectively, corresponding to diradical lifetimes of ca. 0.5 µs. These unexpectedly high barriers have been verified by MM3 force-field calculations and by an investigation of the kinetics of the gas-phase thermolysis of 12 (to give 13 and 16 which is an epimer of 12 and 13) and of 13 (to give 12 and 16). When the [a]

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Section: The Thermal [2؉2] Cyclodimerisation Of (2e4z)-24-cyclooctamentioning

confidence: 99%

Section: Elucidation Of Molecular Structures ؊ Synthetic Aspectsmentioning

confidence: 99%

Section: Cyclobuta[12][8]annulene (16) (A) By Thermolysis Of 12mentioning

confidence: 99%

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The Thermal [2+2] Cyclodimerisation of (E,Z)-Cycloocta-1,3-diene Revisited − Chemical Trapping and Properties of the Intermediate 1,4-Diradicals

et al. 2002

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“…The DBMBF, triplet energy has been determined to be 62 kcallmol (1 1). There is a train of critical studies reported from various groups claiming that these enones have different reactive states for various photoreactions (22)(23)(24)(25)(26)(27). For IOi, it is most likely that ground state trans-2-cyclooctenone is generated from DBMBF, sensitization and undergoes dimerization in analogy to the results from direct excitation (22), though direct photolysis in CH,CN gave a complex mixture in our hands without giv- For personal use only.…”

Section: Discussionmentioning

confidence: 82%

“…It is speculated that trans-2-cyclooctenone, being a twisted ground state molecule (22), has a long lifetime, and can be photolysed to give other products. For 10h and 4,4-dimethyl-2-cyclohexenone, a twisted (or relaxed) state, either on the ground (26) or an excited state energy surface (25), has been suggested to undergo dimerization, cycloaddition, and rearrangement (23)(24)(25)(26)(27).…”

Section: Discussionmentioning

confidence: 99%

The photocycloaddition of dibenzoylmethanatoboron difluoride (DBMBF₂) with conjugated enones and en-esters

Chow¹,

Wang²,

Xiang³

1993

Can. J. Chem.

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YUAN L. CHOW, SHI-SEN WANG, and XIAN-EN CHENG. Can. J. Chem. 71, 846 (1993). Dibenzoylmethanatoboron difluoride (DBMBF,), the BF, complex of dibenzoylmethane, reacted from its singlet excited state with a,P-unsaturated ketones and esters to give 1,5-diketones by a [2+2] cycloaddition and ring-opening sequence in an analogous pathway to that observed in the photocycloaddition to olefins and dienes. The present photoreaction is unexpected since conjugated enones and en-esters are poor electron donors to comply with the previously proposed charge transfer requirement in DBMBF, photoreactions. The photocycloaddition to these substrates was highly regioselective and stereoselective, giving the head-to-head orientation, which could be enhanced by a-methyl substitution; P-methyl substitution increased the alternate head-to-tail orientation. The photolysis of a mixture of DBMBF, and a cyclic enone also caused the latter to dimerize to give head-to-head and head-to-tail dimers in significant yields. These photodimerizations were apparently caused by DBMBF, sensitization. The mechanism of the sensitization is discussed. [Traduit par la rCdaction1

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The Thermal [2+2] Cyclodimerisation of (E,Z)-Cycloocta-1,3-diene Revisited − Chemical Trapping and Properties of the Intermediate 1,4-Diradicals

et al. 2002

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trans-2-Cyclooctenone

Cited by 65 publications

References 2 publications

The Thermal [2+2] Cyclodimerisation of (E,Z)-Cycloocta-1,3-diene Revisited − Chemical Trapping and Properties of the Intermediate 1,4-Diradicals

The Thermal [2+2] Cyclodimerisation of (E,Z)-Cycloocta-1,3-diene Revisited − Chemical Trapping and Properties of the Intermediate 1,4-Diradicals

The photocycloaddition of dibenzoylmethanatoboron difluoride (DBMBF₂) with conjugated enones and en-esters

The Thermal [2+2] Cyclodimerisation of (E,Z)-Cycloocta-1,3-diene Revisited − Chemical Trapping and Properties of the Intermediate 1,4-Diradicals

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trans-2-Cyclooctenone

Cited by 65 publications

References 2 publications

The Thermal [2+2] Cyclodimerisation of (E,Z)-Cycloocta-1,3-diene Revisited − Chemical Trapping and Properties of the Intermediate 1,4-Diradicals

The Thermal [2+2] Cyclodimerisation of (E,Z)-Cycloocta-1,3-diene Revisited − Chemical Trapping and Properties of the Intermediate 1,4-Diradicals

The photocycloaddition of dibenzoylmethanatoboron difluoride (DBMBF2) with conjugated enones and en-esters

The Thermal [2+2] Cyclodimerisation of (E,Z)-Cycloocta-1,3-diene Revisited − Chemical Trapping and Properties of the Intermediate 1,4-Diradicals

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The photocycloaddition of dibenzoylmethanatoboron difluoride (DBMBF₂) with conjugated enones and en-esters