Modular Synthesis, Orthogonal Post‐Functionalization, Absorption, and Chiroptical Properties of Cationic [6]Helicenes

Torricelli, Franck; Bosson, Johann; Besnard, Céline; Chekini, Mahshid; Bürgi, Thomas; Lacour, Jérôme

doi:10.1002/ange.201208926

Cited by 32 publications

(12 citation statements)

References 60 publications

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“…Two synthetic pathways to helicenium ions have been reported. A stepwise route, in which a xanthone‐like structure is formed and then treated with a carbon nucleophile to incorporate the third arm into the structure,7e, 10 or a direct route, in which the molecular framework is initially formed and then bridged by either external attack by primary amines or internal attack by hydroxy groups released by ether cleaving reagents 7a. 9a, b, d, 11c, 17 In this work, DMCA + was synthesised by the second route, as presented in Scheme .…”

Section: Resultsmentioning

confidence: 99%

Synthesis and Structures of N‐Alkyl‐1,13‐dimethoxychromeno‐ [2,3,4‐kl]acridinium Salts: The Missing Azaoxa[4]helicenium

Sørensen

Madsen

Laursen

2014

Chemistry A European J

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Helical structures are interesting due to their inherent chirality. Helicenium ions are triarylmethylium structures twisted into configurationally stable helicenes through the introduction of two heteroatom bridges between the three aryl substituents. Of the configurationally stable [4]helicenium ions, derivatives with sulfur, oxygen and nitrogen bridges have already been synthesised. However, one [4]helicenium ion has proven elusive, until now. We present herein the first synthesis of the 1,13-dimethoxychromeno[2,3,4-kl]acridinium (DMCA(+)) [4]helicenium ion. A series of six differently N-substituted DMCA(+) ions as their hexafluorophosphate salts are reported. Their cation stability was evaluated and it was found that DMCA(+) is ideally suited as a phase-transfer catalyst with a pKR+ of 13.0. The selectivity of nucleophilic addition to the central carbon atom of DMCA(+) has been demonstrated with diastereotopic ratios of up to 1:10. The single-crystal structures of several of the DMCA(+) salts were determined, and structural differences between N-aryl- and N-alkyl-substituted cations were observed. The results of a comparative study of the photophysics of the [4]helicenium ions are presented. DMCA(+) is found to be a potent red-emitting dye with a fluorescence quantum yield of 20 % in apolar solvents and a fluorescence lifetime of 12 ns. [4]Helicenium ions, including DMCA(+), all suffer from solvent-induced quenching, which reduces the fluorescence quantum yields significantly (ϕfl < 5 %) in polar solvents. A difference in photophysical properties is observed between N-aryl- and N-alkyl-substituted DMCA(+), which has tentatively been attributed to a difference in molecular conformation.

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Section: Resultsmentioning

confidence: 99%

Synthesis and Structures of N‐Alkyl‐1,13‐dimethoxychromeno‐ [2,3,4‐kl]acridinium Salts: The Missing Azaoxa[4]helicenium

Sørensen

Madsen

Laursen

2014

Chemistry A European J

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“…[11] Yet, the neutral radical state of the DMQA system has so far not been reported. Structural analogues to these carbenium ions are the neutral, nitrogen-centred [4]heterohelicenes first reported by Hellwinkel et al, [12] and Venkataraman et al later reported and studied the [5]-and [6]heterohelicenes in detail.…”

Section: Introductionmentioning

confidence: 97%

“…The [4]helicenium ion with two oxa bridges (N-alkyl-1,13-dimethoxychromenoxanthenium, DMCX + ) and the asymmetrical derivative with one aza and one oxa bridge (1,13-dimethoxychromenoacridinium, DMCA + ) have since been reported. [3][4][5] Recently, the first synthesis of [6]helicenium ions was achieved, albeit without methoxy groups in the positions equivalent to 1 and 13 in the [4]helicenium structure. [6] DMQA + is a highly configurationally stable, chiral, cationic dye.…”

Section: Introductionmentioning

confidence: 99%

“…[3][4][5] Recently, the first synthesis of [6]helicenium ions was achieved, albeit without methoxy groups in the positions equivalent to 1 and 13 in the [4]helicenium structure. [6] DMQA + is a highly configurationally stable, chiral, cationic dye. The dye properties have been investigated, and a high degree of solvent-sensitive behaviour was observed.…”

Section: Introductionmentioning

confidence: 99%

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Synthesis and Stability of N,N′‐Dialkyl‐1,13‐dimethoxyquinacridinium (DMQA⁺): A [4]Helicene with Multiple Redox States

2014

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N,N′‐Dialkyl‐1,13‐dimethoxyquinacridinium (DMQA+) is a configurationally locked [4]helicene, a stable carbenium ion and a potent near‐infrared emitter. The versatile synthesis and resolution into M and P enantiomers has made DMQA+ and its congener helicenium derivatives attractive chiral dyes and building blocks. In the present study, electrochemical and spectroscopic studies showed that several redox states of DMQA+ are accessible and stable. The cation stability towards nucleophiles is determined and it is shown that the addition of OH− proceeds with a surprisingly low rate of reaction. The synthetic methodologies leading to DMQA+ are described, and the chemistry occurring from the different redox states of DMQA is identified. This [4]helicene is shown to be a unique molecular framework that is stable as a neutral radical and very stable as a carbenium ion.

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“…14,15 Comparatively less studied are cationic helicenoids ( Figure 1). [16][17][18][19][20][21][22][23][24][25][26][27][28] Representative examples are heterohelicenium systems studied by Lacour group 20 or helical dications called helquats developed by our group. 23 These and similar cationic systems promise attractive range of properties and applications [29][30][31][32][33][34][35][36][37][38] that may be complementary to non-ionic helicenes.…”

Section: Introductionmentioning

confidence: 99%

Dutch Resolution of a configurationally stable [5]helquat

et al. 2018

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Synthesis and nontrivial optical resolution of a helicene-like dication, helquat 1, has been accomplished. Starting with gram scale of the racemic helquat 1 sample, Dutch Resolution using family of 3 tartrate anions was key to achieve successful separation of M and P helical enantiomers of 1. Hundreds of milligrams of each enantiomer of this configurationally stable C -symmetric helquat have been obtained. Racemization barrier of 1 has been determined. To our knowledge this is the first report on Dutch Resolution performed with a helicene-like compound. Moreover, there are no literature precedents for Dutch Resolution of chiral quaternary ammonium cations.

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Modular Synthesis, Orthogonal Post‐Functionalization, Absorption, and Chiroptical Properties of Cationic [6]Helicenes

Cited by 32 publications

References 60 publications

Synthesis and Structures of N‐Alkyl‐1,13‐dimethoxychromeno‐ [2,3,4‐kl]acridinium Salts: The Missing Azaoxa[4]helicenium

Synthesis and Structures of N‐Alkyl‐1,13‐dimethoxychromeno‐ [2,3,4‐kl]acridinium Salts: The Missing Azaoxa[4]helicenium

Synthesis and Stability of N,N′‐Dialkyl‐1,13‐dimethoxyquinacridinium (DMQA⁺): A [4]Helicene with Multiple Redox States

Dutch Resolution of a configurationally stable [5]helquat

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Modular Synthesis, Orthogonal Post‐Functionalization, Absorption, and Chiroptical Properties of Cationic [6]Helicenes

Cited by 32 publications

References 60 publications

Synthesis and Structures of N‐Alkyl‐1,13‐dimethoxychromeno‐ [2,3,4‐kl]acridinium Salts: The Missing Azaoxa[4]helicenium

Synthesis and Structures of N‐Alkyl‐1,13‐dimethoxychromeno‐ [2,3,4‐kl]acridinium Salts: The Missing Azaoxa[4]helicenium

Synthesis and Stability of N,N′‐Dialkyl‐1,13‐dimethoxyquinacridinium (DMQA+): A [4]Helicene with Multiple Redox States

Dutch Resolution of a configurationally stable [5]helquat

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Synthesis and Stability of N,N′‐Dialkyl‐1,13‐dimethoxyquinacridinium (DMQA⁺): A [4]Helicene with Multiple Redox States