Nuclear magnetic resonance spectra of cyclic 1,3-diphenylallyl cations. 1,3-Orbital interaction

The pp* triplet excited states of 3-phenyl-2-cyclohexenone (1) and 3-phenyl-2-cyclopentenone (2) have been observed by time-resolved infrared (TRIR) spectroscopy. The reaction of various alkenes with the triplet excited state of 2 has also been studied by TRIR spectroscopy, and the partitioning between fragmentation and ring closure of the biradical intermediates involved has been estimated. Within a series of structurally related biradicals, more stable ones undergo ring closure more efficiently. Scheme 1 Representative enone-alkene [2 + 2] reactions. y Dedicated to Professor Dr Z. R. Grabowski and Professor Dr J. Wirz on the occasions of their 75th and 60th birthdays. z Electronic supplementary information (ESI) available: Optimized geometries and ab initio-calculated IR frequencies and intensities for cyclic enones. See

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“…1. To aid peak assignments, 18 O-labeled 1 and 2 were synthesized 21 and the TRIR difference spectra recorded (Fig. 1).…”

Section: Resultsmentioning

confidence: 99%

“…The synthesis of enones 1 and 2 was carried out according to literature procedures. 21 The synthesis of 18 O-labeled 1 and 2 was carried out substituting 18 O-water for unlabeled water.…”

Section: Methodsmentioning

confidence: 99%

Time-resolved IR studies of cyclic enone triplet excited states and their reactions with alkenes

Cohen

Showalter

Brady

et al. 2003

Phys. Chem. Chem. Phys.

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“…The 1 H NMR analysis of trans -1,3-disubstituted cyclobutanes has shown that the cyclobutyl ring undergoes rapid conformational flips, making the cyclobutyl protons symmetrically equivalent and resulting in the methine signal (2 × CH-1/3) being a pentet and the methylene (2 × CH 2 -2/4) being a triplet. − However, this was not the case for 1,2-disubstituted cyclobutanes. In an NMR study of cis and trans isomers of 1,2-diphenylcyclobutane, 1 H NMR homodecoupling was used to obtain all J HH coupling constants, showing that the trans isomer is rigid with the two phenyls in a diequatorial conformation and the cis isomer flips between two conformations each with one pseudoequatorial phenyl and one pseudoaxial phenyl group; this results in both isomers possessing methine (2 × CH-1/3) and methylene (2 × CH 2 -2/3) signals resonating as three multiplets. , …”

Section: Resultsmentioning

confidence: 99%

Orthoscuticellines A–E, β-Carboline Alkaloids from the Bryozoan Orthoscuticella ventricosa Collected in Australia

et al. 2020

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Antiplasmodial high-throughput screening of extracts derived from marine invertebrates collected from northern NSW, Australia, resulted in the methanol extract of the bryozoan Orthoscuticella ventricosa being identified as inhibitory toward the 3D7 strain of Plasmodium falciparum. Purification of this extract resulted in two new bis-β-carbolines that possess a cyclobutane moiety, orthoscuticellines A and B (1 and 2), three new β-carboline alkaloids, orthoscuticellines C−E (3−5), and six known compounds, 1-ethyl-4methylsulfone-β-carboline ( 6), 1-ethyl-β-carboline ( 7), 1-acetyl-β-carboline (8) 1-(1′-hydroxyethyl)-β-carboline ( 9), 1-methoxycarbonyl-β-carboline (10), and 1-vinyl-β-carboline (11). The structures of all compounds were determined from analysis of MS and 1D and 2D NMR data. The compounds showed modest antiplasmodial activity against P. falciparum in the range of 12−21 μM.

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“…3-Phenylcyclopentenone and 3-phenylcyclohexenone were prepared as described previously. 14 These enones were purified by vacuum sublimation (90 ЊC, 4 × 10 Ϫ2 mbar) and recrystallisation from ethyl acetate. Elemental analysis for 3-phenylcyclopentenone (Found: C, 83.35; H, 6.31.…”

Section: Methodsmentioning

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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Nuclear magnetic resonance spectra of cyclic 1,3-diphenylallyl cations. 1,3-Orbital interaction

Cited by 17 publications

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Time-resolved IR studies of cyclic enone triplet excited states and their reactions with alkenes

Time-resolved IR studies of cyclic enone triplet excited states and their reactions with alkenes

Orthoscuticellines A–E, β-Carboline Alkaloids from the Bryozoan Orthoscuticella ventricosa Collected in Australia

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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