Synthesis and dynamics of the corannulene nucleus

Borchardt, Allen; Fuchicello, Augusto; Kilway, Kathleen V.; Baldridge, Kim K.; Siegel, Jay S.

doi:10.1021/ja00031a080

Cited by 253 publications

(156 citation statements)

References 1 publication

(1 reference statement)

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“…Whilst 2 has a D 6h structure both in solution and in the solid state [9], 1 is bowl-shaped in the solid state [10] but has a time-averaged planar D 5h structure in solution (as established by temperature-dependent 1 H NMR) due to rapid bowl-to-bowl interconversion [11,12]. In contrast, 3 has a saddle-shaped structure of C 2 symmetry (3b) in the solid state [8] and a time-averaged planar structure of D 7h symmetry (3a) in solution (with one 1 H and three 13 C NMR resonances), which is not frozen out even at À90°C [13] (Fig.…”

Section: Introductionmentioning

confidence: 99%

A simple model for counter-rotating ring currents in [n]circulenes

Acocella

Havenith

Steiner

et al. 2002

Chemical Physics Letters

100

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Ab initio current density maps for [7]circulene computed using the ipsocentric CTOCD-DZ/6-31G**//RHF/6-31G** method show that in both planar [3a (D 7h Þ] and non-planar, saddle-shaped [3b (C 2 Þ] geometries this molecule sustains similar counter-rotating rim (diatropic) and hub (strongly paratropic) currents. A survey of the orbital contributions to the current density reveals that 3 like corannulene (1) is a 4d + 4p system with just eight magnetically active and 20 magnetically inactive p electrons. The graph-theoretical H€ u uckel-London model describes the ring-current patterns of [n]circulenes in terms of a coupling strength (the ratio of radial and tangential resonance integrals) that charts the variation from the decoupled con-rotating currents of the [n]annulene-within-an-[m]annulene model to the fully coupled counter-rotating currents of the real [n]circulene. Ó

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Section: Introductionmentioning

confidence: 99%

A simple model for counter-rotating ring currents in [n]circulenes

Acocella

Havenith

Steiner

et al. 2002

Chemical Physics Letters

100

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“…The first synthesis of the pristine corannulene was accomplished in 1966 by applying a long synthetic route [68]. The synthetic investigation was postponed until Scott et al [69] and Siegel et al [70] reinitiated the synthesis of corannulene with a succinct synthetic route by using the flash vacuum pyrolysis (FVP) method in the early 1990s. In the FVP method, the planar π-conjugated precursors are directly converted into buckybowls under high temperature to yield a racemic mixture [71].…”

Section: Asymmetric Synthesis Of Buckybowl and Azabuckybowlmentioning

confidence: 99%

Chiral Buckybowl Molecules

Kanagaraj

Lin

et al. 2017

Symmetry

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Buckybowls are polynuclear aromatic hydrocarbons that have a curved aromatic surface and are considered fragments of buckminsterfullerenes. The curved aromatic surface led to the loss of planar symmetry of the normal aromatic plane and may cause unique inherent chirality, so-called bowl chirality, which it is possible to thermally racemize through a bowl-to-bowl inversion process. In this short review, we summarize the studies concerning the special field of bowl chirality, focusing on recent practical aspects of attaining diastereo/enantioenriched chiral buckybowls through asymmetric synthesis, chiral optical resolution, selective chiral metal complexation, and chiral assembly formation.

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“…Corannulene, C 20 H 10 , was first prepared in minuscule yields by Barth and Lawton in a herculean 17-step process [36]; its non-planar twenty-carbon framework is a substantial substructure of the fullerene C 60 . Subsequently, in a synthetic tour de force, Scott devised a much shorter and more efficient route [37], and Siegel has since developed the synthesis to the point where corannulene is now available in kilogram quantities [38], thus allowing the study of its own dynamic behavior as well as that of numerous derivatives. The barrier to umbrella-like bowl-to-bowl inversion, illustrated in Figure 6, involves the interconversion of C 5v symmetric entities via a planar D 5h transition state.…”

Section: -(S)mentioning

confidence: 99%

Symmetry Breaking in NMR Spectroscopy: The Elucidation of Hidden Molecular Rearrangement Processes

McGlinchey¹

2014

Symmetry

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Variable-temperature NMR spectroscopy is probably the most convenient and sensitive technique to monitor changes in molecular structure in solution. Rearrangements that are rapid on the NMR time-scale exhibit simplified spectra, whereby non-equivalent nuclear environments yield time-averaged resonances. At lower temperatures, when the rate of exchange is sufficiently reduced, these degeneracies are split and the underlying "static" molecular symmetry, as seen by X-ray crystallography, becomes apparent. Frequently, however, such rearrangement processes are hidden, even when they become slow on the NMR time-scale, because the molecular point group remains unchanged. Judicious symmetry breaking, such as by substitution of a molecular fragment by a similar, but not identical moiety, or by the incorporation of potentially diastereotopic (chemically non-equivalent) nuclei, allows the elucidation of the kinetics and energetics of such processes. Examples are chosen that include a wide range of rotations, migrations and other rearrangements in organic, inorganic and organometallic chemistry.

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Synthesis and dynamics of the corannulene nucleus

Cited by 253 publications

References 1 publication

A simple model for counter-rotating ring currents in [n]circulenes

A simple model for counter-rotating ring currents in [n]circulenes

Chiral Buckybowl Molecules

Symmetry Breaking in NMR Spectroscopy: The Elucidation of Hidden Molecular Rearrangement Processes

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