Benzannulated annulenes. 9. Toward the understanding of benzannulated annulenes: a simple correlation of the diatropicity of several benzannulated dihydropyrenes in terms of bond order deviations with predictions for other benzannulenes

Mitchell, Reginald H.; Williams, Richard Vaughan; Mahadevan, Ramanathan; Lai, Yongqing; Dingle, Thomas W.

doi:10.1021/ja00373a039

Cited by 39 publications

(25 citation statements)

References 3 publications

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“…Effect of Conjugation. A simple correlation of the diatropicity of benzannelated dihydropyrenes in terms of bond order deviation has been employed successfully to predict the chemical shift of the methyl protons in derivatives of 1 . Similar calculations on 6 and 11 in our work afforded the results summarized in Table .…”

Section: Resultsmentioning

confidence: 99%

Synthesis and Diatropicity of trans-10b,10c-Dimethylacenaphthyleno[1,2:e]-10b,10c-dihydropyrene: A Model Aromatic Molecule To Verify the Effect of Conjugation on the Diatropicity of an Annulene

1997

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The title compound 11 was synthesized from acenaphthenequinone in 11 steps with an overall yield of ca. 1.3%. Photochemical desulfurization of the thiacyclophanene 24 afforded the cyclophanene 28. Photochemical isomerization of 28 to the tetrahydropyrene derivative 32 followed by DDQ oxidation gave the desired dihydropyrene 11. Compound 11 is found to sustain only about 85% of the ring current of the parent dihydropyrene 1. On the basis of our results, a significant effect on the diatropicity of the 14π annulene in 11 due to its conjugation with a naphthalene moiety is verified. A correlation between theoretically calculated bond orders and experimentally observed coupling constants for selected bonds in 11 indicates that the inductive effect, relative to the resonance effect, plays a major role in the net effect of conjugation observed in 11. Among several derivatives of dihydropyrene 1, a linear relationship is observed for an empirical correlation between the methyl chemical shifts and the corresponding Dewar resonance energies associated with the benzenoid systems in conjugation with 1. This may serve as a method to estimate the resonance energies of other aromatic systems relative to that of benzene. Compound 11 underwent electrophilic nitration, acetylation, and bromination readily under mild conditions. The electrophiles reacted selectively with the dihydropyrene system in 11 and not the acenaphthylene moiety in conjugation.

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Section: Resultsmentioning

confidence: 99%

Synthesis and Diatropicity of trans-10b,10c-Dimethylacenaphthyleno[1,2:e]-10b,10c-dihydropyrene: A Model Aromatic Molecule To Verify the Effect of Conjugation on the Diatropicity of an Annulene

1997

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“…The explanation is given in the 1990 paper, 63 and principally rests on looking at the relative resonances of the annulene vs. the annulated moiety. In a series of papers, [64][65][66][67][68] Mitchell showed that when a benzene is annulated (3 and 4), the chemical shift of the central H and Me is shifted downfield by 4.14 and 2.65 ppm, respectively, for 3, and by 2.4 ppm for 4. For 5 and 6, it was found that the chemical shift of the central Me groups is 0.02 and À3.58 ppm, respectively.…”

Section: Nmrmentioning

confidence: 99%

Magnetic criteria of aromaticity

2015

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This review describes the current state of magnetic criteria of aromaticity. The introduction contains the fundamentals of ring currents in aromatic and antiaromatic systems, followed by a brief description of experimental and computational tools: NMR, diamagnetic susceptibility exaltation, current density analyses (CDA) and nucleus independent chemical shifts (NICS). This is followed by more comprehensive chapters: NMR - focusing on the work of R. Mitchell - NICS and CDA - describing the progress and development of the methods to their current state and presenting some examples of representative work.

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“…Numerous recent studies have shown that Boekelheide's trans -15,16-dimethyl-dihydropyrene (DMDHP) 1 , a 14π-diatropic annulene, with its highly shielded internal methyl groups is a sensitive probe for monitoring the ring current effects and aromaticity in annulenes (Figure ). − …”

Section: Introductionmentioning

confidence: 99%

“…The syntheses of [a]ring- and [e]ring-benzannelated dihydropyrenes ,, and their PAH-fused analogues (e.g., naphtho-, pyreno-, phenanthro-, biphenyleno-, and acenaphthyleno-DMDHP) 4,8-10 have been accomplished. Several heteroaromatic-fused counterparts (e.g., furan and thiophene) were also synthesized, and their ring current effects were examined. , …”

Section: Introductionmentioning

confidence: 99%

Generation of the First Series of Oxonium−Annulenium Dications from trans-15,16-Dimethyldihydropyrene DMDHP: A Diatropic → Paratropic → Diatropic/Paratropic Manifold by Mono- and Diprotonation

Laali¹,

Tanaka²,

Mitchell³

et al. 1998

J. Org. Chem.

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The 2-formyl derivative of trans-dimethyldihydropyrene DMDHP 5 is monoprotonated with FSO 3 H/ SO 2 ClF and diprotonated with FSO 3 H·SbF 5 (4:1)/SO 2 ClF to form persistent carboxonium monocation 5H + and carboxonium-annulenium dication 5H 2 2+ , respectively. With the cyclohexenone-fused 8 and cyclopentenone-fused 9 derivatives, the tendency to diprotonate increases, whereby dications 8H 2 2+ and 9H 2 2+ are cleanly generated in FSO 3 H/SO 2 ClF. However, the monocation 8H + could be produced in HOAc·TFAH/CD 2 Cl 2 under exchanging conditions. For 9, diprotonation competes even at these low acidities; the isomeric 10 behaved similarly. The biscyclopentenone-fused derivatives 11 and 12 form bisoxonium ions in TFAH/CD 2 Cl 2 and Lewis acid complexes with SnCl 4 . The transoid form has a stronger tendency to exist in equilibrium with ring protonation. The charge delocalization pathway in the annulene ring are deduced in the cations and compared with the previously studied ring protonated 12-annulenium ions derived from parent 1 and its 2-nitro and 2-bromo derivatives. Examination of the shielding/deshielding trends in the internal methyl protons and the annulene ring protons is used to shed light on the ring current effects in the mono-and dications. The charge delocalization mode at the periphery of the annulenium cation is also evaluated on the basis of magnitude of ∆δ 13 C values. AM1 calculations were used to obtain the relative protonation energies for various sites for comparison with the experiment. Diprotonation of the 2,7-dinitro derivative 13 and oxidation of parent 1 were also examined.

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Benzannulated annulenes. 9. Toward the understanding of benzannulated annulenes: a simple correlation of the diatropicity of several benzannulated dihydropyrenes in terms of bond order deviations with predictions for other benzannulenes

Cited by 39 publications

References 3 publications

Synthesis and Diatropicity of trans-10b,10c-Dimethylacenaphthyleno[1,2:e]-10b,10c-dihydropyrene: A Model Aromatic Molecule To Verify the Effect of Conjugation on the Diatropicity of an Annulene

Synthesis and Diatropicity of trans-10b,10c-Dimethylacenaphthyleno[1,2:e]-10b,10c-dihydropyrene: A Model Aromatic Molecule To Verify the Effect of Conjugation on the Diatropicity of an Annulene

Magnetic criteria of aromaticity

Generation of the First Series of Oxonium−Annulenium Dications from trans-15,16-Dimethyldihydropyrene DMDHP: A Diatropic → Paratropic → Diatropic/Paratropic Manifold by Mono- and Diprotonation

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