1H and 13C NMR assignments of the three dicyclopenta-fused pyrene congeners

Otero-Lobato, María José; Walree, Cornelis A. van; Havenith, Remco W. A.; Jenneskens, Leonardus W.; Fowler, Patrick W.; Steiner, Erich

doi:10.1016/j.tet.2006.03.033

Cited by 3 publications

(3 citation statements)

References 33 publications

(12 reference statements)

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“…157,158 However, it has been suggested that current density maps of the type calculated by Lazzeretti and co-workers [159][160][161][162][163][164][165] and Fowler and co-workers [166][167][168][169][170][171][172][173][174][175] give a more accurate description of electronic ring currents in aromatic systems than do NICS. The NICS calculated at the center of an aromatic ring has been suggested as a measure of aromaticity or antiaromaticity.…”

Section: Intermolecular Effectsmentioning

confidence: 99%

Ab initio calculations of NMR chemical shifts

Casabianca

Dios²

2008

The Journal of Chemical Physics

108

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The nuclear magnetic resonance chemical shift is one of the most powerful properties available for structure determination at the molecular level. A review of advances made in the ab initio calculation of chemical shielding during the past five years is presented. Specifically, progress in the areas including the effects of an unpaired electron, electron correlation, and relativistic effects into ab initio chemical shielding calculations, the tensor nature of the chemical shift, and intramolecular and intermolecular effects on the chemical shift will be covered.

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Section: Intermolecular Effectsmentioning

confidence: 99%

Ab initio calculations of NMR chemical shifts

Casabianca

Dios²

2008

The Journal of Chemical Physics

108

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“…Among them, the cyclopenta-fused pyrenes are an important class of CP-PAHs owing to their unique physical and photophysical properties, such as high electron affinities and anomalous fluorescence [17][18][19][20]. However, the reported synthetic methods towards the (di-)cyclopenta-fused pyrene congeners (i-iii, Scheme 1) have mainly been reliant on the flash vacuum pyrolysis of suitable precursors under harsh conditions (T ≥ 900 °C), which resulted in relatively low yields [ [21][22][23][24]. Palladium-catalyzed annulation has been recently proven as an efficient route to get access to aromatic hydrocarbons with peri-fused five-membered rings [25][26][27].…”

Section: Introductionmentioning

confidence: 99%

One-pot synthesis of dicyclopenta-fused peropyrene via a fourfold alkyne annulation

Liu

et al. 2020

Beilstein J. Org. Chem.

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A novel dicyclopenta-fused peropyrene derivative 1 was synthesized via a palladium-catalyzed four-fold alkyne annulation of 1,3,6,8-tetrabromo-2,7-diphenylpyrene (5) with diphenylacetylene. The annulative π-extension reaction toward 1 involved a twofold [3 + 2] cyclopentannulation and subsequent twofold [4 + 2] benzannulation. The structure of 1 is unambiguously confirmed by X-ray crystallography; 1 adopted a twisted geometry due to the steric hindrance of the phenyl rings and the hydrogen substituents at the bay regions. Notably, compound 1 exhibits a narrow energy gap (1.78 eV) and a lower LUMO energy level than the parent peropyrene without the fusion of the five-membered rings. In addition, the effects of the peri-fused pentagons on the aromaticity and molecular orbitals of 1 were evaluated by theoretical calculations. This work presents an efficient method to develop π-extended aromatic hydrocarbons with cyclopenta moieties.

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“…As illustrated in Fig. 2a, the peak signals at 8.30-7.80 ppm can be assigned to pyrene aromatic protons 32,33 and the peak signals at around 1.4 ppm should correspond to the methyl groups of Boc, 34 and the peak signal at 7.7 ppm should have resulted from the -ONH-group next to methylene. The 1 H NMR spectrum of pyrene-ONH 2 is shown in Fig.…”

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confidence: 98%