Synthesis of Dipleiadiene by “Serendipity”

Vogel, Emanuel; Neumann, B.; Klug, W.; Schmickler, Hans; Lex, Johann

doi:10.1002/anie.198510461

Cited by 27 publications

(17 citation statements)

References 30 publications

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“…Dihydroimidacene is clearly not globally aromatic, as the singlet at 5.86 ppm is similar to those of the corresponding vinylic protons in simple [16] and bridged macrocyclic [4n]annulenes. [17] Complementary to the 1 H NMR spectrum, seven signals occur in the 13 C NMR spectrum; the resonance at 113.8 ppm is assigned to the sp 2 -hybridized carbon atoms of the CHCH bridges.…”

Section: Resultsmentioning

confidence: 99%

Global versus Local Aromaticity in Porphyrinoid Macrocycles: Experimental and Theoretical Study of “Imidacene”, an Imidazole‐Containing Analogue of Porphycene

Sargent

Hawkins

Allen

et al. 2003

Chemistry A European J

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The synthesis, spectroscopic properties, and computational analysis of an imidazole-based analogue of porphycene are described. The macrocycle, given the trivial name ™imidacene∫, was prepared by reductive coupling of a diformyl-substituted 2,2'-biimidazole using low-valent titanium, followed by treatment with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone. Imidacene displays a porphyrin-like electronic structure, as judged by its 1 H NMR, 13 C NMR, and UV/Vis spectral characteristics. Despite a cyclic 18 p-electron pathway, dichloromethane or ethyl acetate solutions of imidacene were found to undergo rapid decomposition, even in the absence of light and air. A series of high-level theoretical calculations, performed to probe the origin of this instability, revealed that the presence of a delocalized 18 p-electron pathway in both imidacene and porphycene provides less aromatic stabilization energy than locally aromatic 6 p-electron heterocycles in their reduced counterparts. That reduction of imidacene occurs on perimeter nitrogen atoms allows it to maintain its planarity and two stabilizing intramolecular hydrogen bonds, thereby distinguishing it from porphycene and, more generally, from porphyrin. Despite the presence of both 18 p-and 22 pelectron pathways in the planar, reduced form of imidacene, aromaticity is evident only in the 6 p-electron five-membered rings. Our computational analysis predicts that routine 1 H NMR spectroscopy can be used to distinguish between local and global aromaticity in planar porphyrinoid macrocycles; the difference in the chemical shift for the internal NH protons is expected to be on the order of 19 ppm for these two electronically disparate sets of ostensibly similar compounds.

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Section: Resultsmentioning

confidence: 99%

Global versus Local Aromaticity in Porphyrinoid Macrocycles: Experimental and Theoretical Study of “Imidacene”, an Imidazole‐Containing Analogue of Porphycene

Sargent

Hawkins

Allen

et al. 2003

Chemistry A European J

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“…Grossly warped nanographene C 80 H 30 ( 4 in Figure a) contains five heptagons surrounding a pentagon . Herein we report the synthesis, structure, and properties of a new type of aromatic saddle ( 5 in Figure b), which contains a dipleiadiene (Figure b) moiety in a polycyclic framework of 86 sp 2 carbon atoms. As detailed below, the two heptagons in 5 were constructed by ring expansion of bisanthenequinone, an unprecedented strategy for synthesis of negatively curved nanographenes.…”

Section: Figurementioning

confidence: 99%

A Dipleiadiene‐Embedded Aromatic Saddle Consisting of 86 Carbon Atoms

et al. 2018

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This study presents a new type of negatively curved nanographene (C86H32) that contains an unprecedented pattern of heptagons. A tert‐butylated derivative of C86H32 was successfully synthesized using tetrabenzodipleiadiene as a key building block. This synthesis involved a ring expansion reaction as a key step to form the seven‐membered rings in the framework of tetrabenzodipleiadiene. The single‐crystal structure reveals a saddle‐shaped molecule with a highly bent naphthalene moiety at the center of the polycyclic backbone. As found from the DFT calculations, this aromatic saddle is flexible at room temperature and has a saddle‐shaped geometry as the dominant conformation. The DFT calculations along with experimental results show that the attachment of t‐butyl groups to the central tetrabenzodipleiadiene moiety of nanographene C86H32 can stabilize the saddle conformation and make this nanographene less flexible.

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“…The coupling reaction has also proved to be efficient for the synthesis of the bridgehead alkene 73, which exists in the form of the in isomer and served for the study of bicyclic carbocations containing a three-center two-electron CaHaC bond [96][97][98][99], and of the perfluorocyclopentene 74, a versatile intermediate for the development of photochromic materials [100]. The ability of the McMurry reaction to form medium-and large-sized rings efficiently, while at the same time building in considerable strain is also evident in the synthesis of the betweenanene 75 [101] and the heptafulvalene 76; the latter results from a transannular carbonyl coupling reaction and was transformed into displeiadiene after dehydrogenation [102]. A variety of conjugated cyclic polyenes, such as 77 and 78 [103,104], as well as unique examples of cyclo-1,3-dien-5-ynes 79 [105], have been prepared by the intramolecular coupling of dialdehydes.…”

Section: Intermolecular Cross-coupling Reactionsmentioning

confidence: 99%