Chemical and physical properties of 2,3-benzofluorenylidene. Closing the gap between singlet and triplet carbenes

Grasse, Peter B.; Zupancic, Joseph J.; Lapin, Stephen C.; Hendrich, Michael P.; Schuster, Gary B.

doi:10.1021/jo00213a029

Cited by 16 publications

(8 citation statements)

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“…Integration of the NMR absorption of the cyclopropyl hydrogens shows that the two isomeric cyclopropanes are formed in nearly equal amounts regardless of the position of carbene center (Scheme , Table ). The stereochemical outcome of the cyclopropanation depends on the concentration of the styrene if both singlet and triplet states are involved . However, the two cyclopropanes were formed in nearly equal amounts regardless of the initial olefin concentration.…”

Section: Resultsmentioning

confidence: 99%

“…Addition of a carbene to an olefin to form cyclopropane is the classical way to diagnose the multiplicity of the reacting carbene . The stereochemistry of this reaction was probed by employing E -β-deuterio-α-methylstyrene . Integration of the NMR absorption of the cyclopropyl hydrogens shows that the two isomeric cyclopropanes are formed in nearly equal amounts regardless of the position of carbene center (Scheme , Table ).…”

Section: Resultsmentioning

confidence: 99%

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Generation, Reactions, and Kinetics of Di(naphthyl)carbenes: Effects of the Methyl Group

2002

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A series of di(naphthyl)carbenes (DNCs) having methyl groups on aromatic rings were generated by photolysis of the corresponding diazo precursors and studied not only by product analysis, but also by spectroscopic means. "Parent" triplet R-DNC was shown to have a half-life of 70 ms, which is some 30 times larger than that of triplet diphenylcarbene ( 3 DPC), whereas parent triplet β-DNC was 2 orders of magnitude shorterlived than the R-isomer. The lifetimes of triplet DNCs were significantly increased by introducing methyl groups near the carbene center. Thus, 3 R-DNC, which has four methyl groups at 2,2′,4,4′-positions, was shown to have a half-life of 100 ms, and the replacement of the two methyl groups at the 2,2′-positions of this carbene with tri(deuterio)methyl groups resulted in an increase of the lifetime by approximately 3 times by quenching the intramolecular H transfer from the methyl groups to the carbene center leading to o-quinoid compounds. The results are discussed in terms of the counteracting effects of electronic properties stabilizing the singlet state and steric factors favoring the triplet and compared with similar studies with 3 DPCs.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Generation, Reactions, and Kinetics of Di(naphthyl)carbenes: Effects of the Methyl Group

2002

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“…The triplet configuration falls 37.7 kJ mol -1 below singlet in the case of :CH 2 [33]. According to Grasse et al [34] the singlet-triplet energy gap in these reactions is much smaller when H is replaced by aromatic-ring substituents. …”

Section: Figurementioning

confidence: 91%

Effect of Fluorine Substitution on the Reaction between Methylene and Acetone: A DFT Study

Zardoost

Khalilzadeh

Ataei

2014

Progress in Reaction Kinetics and Mechanism

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A theoretical study of the kinetics and mechanism of the reaction between methylene and acetone in the gas phase was performed using the density functional theory method at UB3LYP levels of theory using a 6-311G** basis set. Equilibrium molecular geometries and harmonic vibrational frequencies of the reactants, transition states, intermediates and product were calculated. These calculations showed that the reaction proceeds through an asynchronous concerted mechanism. The effect of fluorine substitution on the reaction rate was investigated: the computed activation barrier exhibits a fairly high sensitivity to the nature of substituents at the C7-and C8-positions. Gibbs free energies of activation for all structures were computed.

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“…The combined organic fractions were evaporated under reduced pressure, to give 30 as red crystals, 1.203 g, yield 87%; mp 134-136 ЊC (lit. 45 mp 138 ЊC). 1 H NMR (CDCl 3 ): δ 7.370 (td, 3 J = 7.1 Hz, 3 J = 6.2 Hz, 4 J = 1.4 Hz, 1H), 7.450 (td, 3 J = 7.0 Hz, 4 J = 1.1 Hz, 1H), 7.478-7.518 (m, 3H), 7.861 (s, 1H, H 5 ), 7.889 (ddd, 3 J = 8.8 Hz, 4 J = 1.3 Hz, 5 J = 0.6 Hz, 1H), 7.968 (ddd, 3 J = 8.2 Hz, 4 J = 1.5 Hz, 5 J = 0.5 Hz, 1H), 8.059 (ddd, 3 J = 8.6 Hz, 4 J = 1.1 Hz, 5 J = 0.8 Hz, 1H), 8.380 (s, 1H, H 10 ).…”

Section: Dispiro[11h-benzo[b]fluorene-112ј-thiirane-3ј9љ-(9љhselenoxa...mentioning

confidence: 99%

Stereochemistry of selenium- and tellurium-bridged heteromerous bistricyclic aromatic enes. The fluorenylidenechalcoxanthene series

Levy

Biedermann

Cohen

et al. 2001

J. Chem. Soc., Perkin Trans. 2

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Chemical and physical properties of 2,3-benzofluorenylidene. Closing the gap between singlet and triplet carbenes

Abstract: Irradiation of 2,3-benzo-11-diazofluorene generates the carbene 2,3-benzo-l 1-fluorenylidene. This carbene

Cited by 16 publications

References 1 publication

Generation, Reactions, and Kinetics of Di(naphthyl)carbenes: Effects of the Methyl Group

Generation, Reactions, and Kinetics of Di(naphthyl)carbenes: Effects of the Methyl Group

Effect of Fluorine Substitution on the Reaction between Methylene and Acetone: A DFT Study

Stereochemistry of selenium- and tellurium-bridged heteromerous bistricyclic aromatic enes. The fluorenylidenechalcoxanthene series

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