1-Synthesis of octa- and nonahelicenes. 2-New syntheses of hexa- and heptahelicenes. 3-Optical rotation and O.R.D. of heptahelicene.

Martin, R. H.; Flammang-Barbieux, M.; Cosyn, J.P.; Gelbcke, Michel

doi:10.1016/s0040-4039(01)99095-1

Cited by 85 publications

(33 citation statements)

References 4 publications

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“…A toluene solution of precursor 3 was irradiated with a high‐pressure Hg lamp at 90 °C for 8 h in the presence of I 2 (oxidant, 3 equiv) and propylene oxide (acid scavenger, 50 equiv) to give [9]helicene ( 4 ) in 67 % yield (Figure 1). The yield of [9]helicene was comparable to reported yields,3b,c, 6a–c and verifies the synthetic guideline proposed above.…”

Section: Methodssupporting

confidence: 87%

“…We, however, avoided the simplest [1]+[1]+[1] and [2]+[2] sequences in the precursor to exclude the formation of an unfavorable [5]helicene framework that easily cyclizes into benzoperylene (Scheme ) 7. The [2]+[1]+[2] sequence was also avoided because it has been reported that this sequence predominantly gives planar dinaphthanthracene rather than the expected [7]helicene (Scheme ) 6a. Based on these considerations, we deduced the following guideline for the design of the precursor olefins: [2] units must be separated by two [1] units.…”

Section: Methodsmentioning

confidence: 99%

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One‐Step Synthesis of [16]Helicene

2015

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A single-strand arylene-vinylene precursor containing four phenylene and three naphthylene units linked together with six vinylene spacers undergoes helical folding via sextuple photocyclization to give a [16]helicene core in a single step. The phenylene and naphthylene units are arranged in the precursor such that unfavorable side reactions (anthracene or benzoperylene formation) are avoided, and this is the key to the success of the one-step synthesis of [16]helicene, which is the longest [n]helicene that has been synthesized to date.

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Section: Methodssupporting

confidence: 87%

Section: Methodsmentioning

confidence: 99%

One‐Step Synthesis of [16]Helicene

2015

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“…Herein, we present the preparation of the first hexapole [9]helicene ( H9H , Figure A), its crystal structure, resolution, optical and electronic properties. The synthetic procedure combines our method for preparing hexapole [7]helicene and the initial approach Martin established in the 1960s for the preparation of various [ n ]helicene, in particular, the [9]helicene in 1968 (Figure B) . It involves a convergent synthesis to stitch together multiple lower helical fragments, here [4]helicene, to make higher homologues.…”

Section: Figurementioning

confidence: 99%

Hexapole [9]Helicene

et al. 2018

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Herein we present the first hexapole [9]helicene (H9H). Co‐catalyzed [2+2+2] cyclotrimerization of a dinaphthopyrene (DNP) functionalized alkyne provides the hexaaryl benzene precursor 2, which is transformed into H9H via a dehydrocyclization reaction. Formation of each embedded [9]helicene involves forging of a new C−C bond, which stitches together two [4]helicene subunits of the neighboring DNP blades, reminiscent of the initial method Martin developed for the preparation of [9]helicene in the 1960s. Single‐crystal X‐ray analysis of both 2 and H9H discloses their extremely distorted and crowded structural features. Chiral resolution, optical and electronic properties of H9H are also presented.

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“…26 Nevertheless, ortho -fusion of an increasing number of benzene rings in pristine helicenes has little effect on the optical absorption and energy gap when higher than [5]helicene. 27−30 To this end, π-extension of helicenes, which can significantly modulate their optical and electronic properties, has been attracting increased attention recently. 31−34 In 2018, Hirose and Matsuda et al reported a hexabenzo-fused [7]helicene ( B , Figure 1a), exhibiting a largely red-shifted absorption and a narrowed optical gap relative to its parent [7]helicene.…”

Section: Introductionmentioning

confidence: 99%

π-Extended Pyrene-Fused Double [7]Carbohelicene as a Chiral Polycyclic Aromatic Hydrocarbon

et al. 2019

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A π-extended double [7]carbohelicene 2 with fused pyrene units was synthesized, revealing considerable intra- and intermolecular π–π interactions as confirmed with X-ray crystallography. As compared to the previous double [7]carbohelicene 1 , the π-extended homologue 2 demonstrated considerably red-shifted absorption with an onset at 645 nm ( 1 : 550 nm) corresponding to a smaller optical gap of 1.90 eV ( 1 : 2.25 eV). A broad near-infrared emission from 600 to 900 nm with a large Stokes shift of ∼100 nm (2.3 × 10 3 cm –1 ) was recorded for 2 , implying formation of an intramolecular excimer upon excitation, which was corroborated with femtosecond transient absorption spectroscopy. Moreover, 2 revealed remarkable chiral stability with a fairly high isomerization barrier of 46 kcal mol –1 , according to density functional theory calculations, which allowed optical resolution by chiral HPLC and suggests potential applications in chiroptical devices.

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1-Synthesis of octa- and nonahelicenes. 2-New syntheses of hexa- and heptahelicenes. 3-Optical rotation and O.R.D. of heptahelicene.

Cited by 85 publications

References 4 publications

One‐Step Synthesis of [16]Helicene

One‐Step Synthesis of [16]Helicene

Hexapole [9]Helicene

π-Extended Pyrene-Fused Double [7]Carbohelicene as a Chiral Polycyclic Aromatic Hydrocarbon

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