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1.
Dr. Long Zhao Prof. Ralf I. Kaiser Dr. Bo Xu Dr. Utuq Ablikim Dr. Musahid Ahmed Mikhail M. Evseev Prof. Eugene K. Bashkirov Prof. Valeriy N. Azyazov Prof. Alexander M. Mebel 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(10):4080-4087
A unified low-temperature reaction mechanism on the formation of acenes, phenacenes, and helicenes—polycyclic aromatic hydrocarbons (PAHs) that are distinct via the linear, zigzag, and ortho-condensed arrangements of fused benzene rings—is revealed. This mechanism is mediated through a barrierless, vinylacetylene mediated gas-phase chemistry utilizing tetracene, [4]phenacene, and [4]helicene as benchmarks contesting established ideas that molecular mass growth processes to PAHs transpire at elevated temperatures. This mechanism opens up an isomer-selective route to aromatic structures involving submerged reaction barriers, resonantly stabilized free-radical intermediates, and systematic ring annulation potentially yielding molecular wires along with racemic mixtures of helicenes in deep space. Connecting helicene templates to the Origins of Life ultimately changes our hypothesis on interstellar carbon chemistry. 相似文献
2.
Myriam Roy Veronika Berezhnaia Marco Villa Nicolas Vanthuyne Michel Giorgi Jean‐Valre Naubron Salom Poyer Valrie Monnier Laurence Charles Yannick Carissan Denis Hagebaum‐Reignier Jean Rodriguez Marc Gingras Yoann Coquerel 《Angewandte Chemie (International ed. in English)》2020,59(8):3264-3271
We report a molecular design and concept using π‐system elongation and steric effects from helicenes surrounding a triphenylene core toward stable chiral polycyclic aromatic hydrocarbons (PAHs) with a maximal π‐distortion to tackle their aromaticity, supramolecular and molecular properties. The selective syntheses, and the structural, conformational and chiroptical properties of two diastereomeric large multi‐helicenes of formula C90H48 having a triphenylene core and embedding three [5]helicene units on their inner edges and three [7]helicene units at their periphery are reported based on diastereoselective and, when applicable, enantiospecific Yamamoto‐type cyclotrimerizations of racemic or enantiopure 9,10‐dibromo[7]helicene. Both molecules have an extremely distorted triphenylene core, and one of them exhibits the largest torsion angle recorded so far for a benzene ring (twist=36.9°). 相似文献
3.
Deepali Waghray Arvid Cloet Prof. Dr. Kristof Van Hecke Dr. Stijn F. L. Mertens Prof. Dr. Steven De Feyter Prof. Dr. Luc Van Meervelt Prof. Dr. Mark Van der Auweraer Prof. Dr. Wim Dehaen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(36):12077-12085
Diazadithia[7]helicenes were synthesized from the readily available building block ethyl 7‐chloro‐8‐formylthieno[3,2‐f]quinoline‐2‐carboxylate by a Wittig reaction–photocyclization strategy. The helicene core was functionalized by nucleophilic aromatic substitution with a variety of nucleophiles (e.g., O‐, N‐, and C‐centered) and palladium‐catalyzed reactions such as Suzuki coupling and Buchwald–Hartwig amination. Racemization studies confirmed that the enantiopure forms of these [7]helicenes are conformationally stable compared to their lower analogues. The solid‐state structures of the novel diazadithia[7]helicenes were determined by single‐crystal X‐ray diffraction. The crystal structures of these azathia[7]helicenes show columnar stacking in antiparallel fashion. The HOMO–LUMO gaps of the new compounds were determined on the basis of electrochemical and optical measurements. 相似文献
4.
Dr. Myriam Roy Dr. Veronika Berezhnaia Dr. Marco Villa Dr. Nicolas Vanthuyne Dr. Michel Giorgi Dr. Jean-Valère Naubron Dr. Salomé Poyer Dr. Valérie Monnier Prof. Dr. Laurence Charles Dr. Yannick Carissan Dr. Denis Hagebaum-Reignier Prof. Dr. Jean Rodriguez Prof. Dr. Marc Gingras Dr. Yoann Coquerel 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(8):3290-3297
We report a molecular design and concept using π-system elongation and steric effects from helicenes surrounding a triphenylene core toward stable chiral polycyclic aromatic hydrocarbons (PAHs) with a maximal π-distortion to tackle their aromaticity, supramolecular and molecular properties. The selective syntheses, and the structural, conformational and chiroptical properties of two diastereomeric large multi-helicenes of formula C90H48 having a triphenylene core and embedding three [5]helicene units on their inner edges and three [7]helicene units at their periphery are reported based on diastereoselective and, when applicable, enantiospecific Yamamoto-type cyclotrimerizations of racemic or enantiopure 9,10-dibromo[7]helicene. Both molecules have an extremely distorted triphenylene core, and one of them exhibits the largest torsion angle recorded so far for a benzene ring (twist=36.9°). 相似文献
5.
《化学:亚洲杂志》2017,12(7):726-729
Aromatic hydroxamic acids (Ar–CO–NOH–Ar′) were used as bidentate chelating ligands to generate the corresponding boron hydroxamate complexes, which were subsequently transformed into nitrogen‐containing helicenes (azahelicenes) using an oxidative photocyclization method that is frequently used for stilbene‐type (Ar–CH=CH–Ar′) precursors of carbohelicenes. The nitrogen atom of the hydroxamate linker was thus directly embedded into the helicene core without using nitrogen‐containing aromatic rings in the stilbene‐type precursors. In a batch photoreaction, aza[4]helicenes were readily and efficiently prepared, but aza[6]helicenes underwent severe decomposition upon irradiation. Alternatively, a continuous flow photoreactor was employed to furnish an amide‐type aza[6]helicene. 相似文献
6.
Johannes Oschwald Dr. David Reger Dr. Stefan Frühwald Vera Warmbrunn Prof. Dr. Andreas Görling Prof. Dr. Norbert Jux Prof. Dr. Thomas Drewello 《Chemphyschem》2023,24(21):e202300496
Gas-phase complexes of [n]helicenes with n=6, 7 and 8 and the silver(I) cation are generated utilizing electrospray ionization mass spectrometry (ESI-MS). Besides the well-established [1 : 1] helicene/Ag+-complex in which the helicene provides a tweezer-like surrounding for the Ag+, there is also a [2 : 1] complex formed. Density functional theory (DFT) calculations in conjunction with energy-resolved collision-induced dissociation (ER-CID) experiments reveal that the second helicene attaches via π-π stacking to the first helicene, which is part of the pre-formed [1 : 1] tweezer complex with Ag+. For polycyclic aromatic hydrocarbons (PAHs) of planar structure, the [2 : 1] complex with silver(I) is typically structured as an Ag+-bound dimer in which the Ag+ would bind to both PAHs as the central metal ion (PAH–Ag+–PAH). For helicenes, the Ag+-bound dimer is of similar thermochemical stability as the π-π stacked dimer, however, it is kinetically inaccessible. Coronene (Cor) is investigated in comparison to the helicenes as an essentially planar PAH. In analogy to the π-π stacked dimer of the helicenes, the Cor−Ag+−Cor−Cor complex is also observed. Competition experiments using [n]helicene mixtures reveal that the tweezer complexes of Ag+ are preferably formed with the larger helicenes, with n=6 being entirely ignored as the host for Ag+ in the presence of n=7 or 8. 相似文献
7.
Long Zhao Ralf I. Kaiser Wenchao Lu Musahid Ahmed Mikhail M. Evseev Eugene K. Bashkirov Valeriy N. Azyazov Christina Tnshoff Florian Reicherter Holger F. Bettinger Alexander M. Mebel 《Angewandte Chemie (International ed. in English)》2020,59(28):11334-11338
A representative, low‐temperature gas‐phase reaction mechanism synthesizing polyacenes via ring annulation exemplified by the formation of pentacene (C22H14) along with its benzo[a]tetracene isomer (C22H14) is unraveled by probing the elementary reaction of the 2‐tetracenyl radical (C18H11.) with vinylacetylene (C4H4). The pathway to pentacene—a prototype polyacene and a fundamental molecular building block in graphenes, fullerenes, and carbon nanotubes—is facilitated by a barrierless, vinylacetylene mediated gas‐phase process thus disputing conventional hypotheses that synthesis of polycyclic aromatic hydrocarbons (PAHs) solely proceeds at elevated temperatures. This low‐temperature pathway can launch isomer‐selective routes to aromatic structures through submerged reaction barriers, resonantly stabilized free‐radical intermediates, and methodical ring annulation in deep space eventually changing our perception about the chemistry of carbon in our universe. 相似文献
8.
Fabio Fenili Clara Rigamonti Alberto Bossi Paolo Ferruti Amedea Manfredi Stefano Maiorana Clara Baldoli Silvia Cauteruccio Emanuela Licandro Elisabetta Ranucci 《Journal of polymer science. Part A, Polymer chemistry》2010,48(21):4704-4710
A tetrathia‐[7]‐helicene bearing in the 2 and 13 positions cyanovinyl groups was used as comonomer in the Michael‐type polyaddition reaction with N,N′‐bis(β‐mercaptoethyl)piperazine. This led to a new polymer bearing tetrathia‐[7]‐helicene units regularly distributed along the polymer backbone, which may be regarded as the first example of a new family of potentially useful nonlinear optical materials. All products were structurally characterized by 1H and 13C NMR spectroscopy. Differential scanning calorimetry characterizations revealed the presence, in both monomeric and polymeric helicenes, of glass‐transition like temperatures, associated to some conformational variation of the helicene units. The optical properties, the film formation and the morphology of the polymer‐containing tetratia‐[7]‐helicenes were also investigated. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 相似文献
9.
Dr. Thomas Biet Arnaud Fihey Dr. Thomas Cauchy Dr. Nicolas Vanthuyne Prof. Christian Roussel Dr. Jeanne Crassous Dr. Narcis Avarvari 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(39):13160-13167
Electroactive fused ethylenedithio? tetrathiafulvalene? [4]helicene and ‐[6]helicenes have been synthesized through a strategy that involved the preparation of 2,3‐dibromo‐helicene derivatives as intermediates. The dihedral angles between the terminal helicenes, as determined by single‐crystal X‐ray analysis, are 22.7° and 50.7° for the [4]helicene and [6]helicene, respectively. Their solid‐state architectures show interplay between S???S and π???π intermolecular interactions. The chiroptical properties of the enantiopure EDT? TTF? [6]helicene derivatives have been investigated and supported by TDDFT calculations. Remarkable redox switching of the circular dichroism (CD) signal between the neutral and radical‐cation species has been achieved. 相似文献
10.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(46):14880-14885
Oxidative fusion reactions of ortho ‐phenylene‐bridged cyclic hexapyrroles and hexathiophenes furnished novel closed helicenes in a selective manner. X‐Ray diffraction analysis unambiguously revealed the structures to be a closed pentaaza[9]helicene, the longest azahelicene reported so far, and an unexpected double‐helical structure of hexathia[9]/[5]helicene, whose formation was assumed to result from multiple oxidative fusion along with a 1,2‐aryl shift. The pentaaza[9]helicene exhibited well‐defined emission with high fluorescence quantum yield (Φ F=0.31) among the known [9]helicenes. Chiral resolution of the racemic pentaaza[9]helicene and hexathia[9]/[5]helicene were achieved by chiral‐phase HPLC and the enantiomers were characterized by circular dichroism spectra and DFT calculations. 相似文献
11.
Anne‐Catherine Bédard Anna Vlassova Augusto C. Hernandez‐Perez André Bessette Prof. Dr. Garry S. Hanan Matthew A. Heuft Prof. Dr. Shawn K. Collins 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(48):16295-16302
Synthesis of helically chiral aromatics resulting from fusion of pyrene and [4]‐ or [5]helicene has been accomplished using photoredox catalysis employing a Cu‐based sensitizer as the key step. Photocyclisation experiments for the synthesis of the target compounds were carried out in batch and using continuous flow strategies. The solid‐state structures, UV/Vis absorption spectra and fluorescence spectra of the pyrene–helicene hybrids were investigated and compared to that of the parent [5]helicene to discern the effects of merging a pyrene moiety within a helicene skeleton. The studies demonstrated that pyrene–helicene hybrids adopt co‐planar or stacked arrangements in the solid state, in contrast to the solid‐state structure of the parent [5]helicene. The UV/Vis and fluorescence spectra of the pyrene–helicene hybrids exhibited strong red‐shifts when compared to the parent [5]helicene. DFT calculations suggest that the strategy of extending the π surface in the y axis of the helicenes increased their HOMO levels while also decreasing their LUMO levels, resulting in significantly reduced band gaps. 相似文献
12.
Teplý F Stará IG Starý I Kollárovic A Saman D Rulísek L Fiedler P 《Journal of the American Chemical Society》2002,124(31):9175-9180
An original approach to helicene frameworks exploiting atom economic isomerization of appropriate energy-rich aromatic cis,cis-dienetriynes has been developed. The new paradigm provides nonphotochemical syntheses of helicenes based on the easy, convergent, and modular assembly of key cis,cis-dienetriynes and their nickel(0)-catalyzed [2+2+2] cycloisomerization. The potential of the methodology is underlined by the syntheses of the parent [5]helicene (2), 7,8-dibutyl[5]helicene (23), [6]helicene (24), and [7]helicene (25). The approach can be adapted to prepare functionalized helicenes as exemplified by the eight-step synthesis of 7,8-dibutyl-2,3-dimethoxy[6]helicene (34). Density functional theory (DFT) calculations showed that bis[2-((1Z)-1-buten-3-ynyl)phenyl]acetylene (1) and isomeric [5]helicene (2) differ enormously in the Gibbs energy content (DeltaG = -136.6 kcal x mol(-1)) to favor highly the devised intramolecular simultaneous construction of three aromatic rings. 相似文献
13.
Marc Joly Nicole Defay Richard H. Martin Jean Paul Declerq Gabriel Germain Bernadette Soubrier-Payen Maurice Van Meerssche 《Helvetica chimica acta》1977,60(2):537-560
Bridged helicenes: 3,15-ethano- and 3,15-(2-oxapropano)-[7]helicene The title compounds ( 35 and 33 , see Scheme 4) have been synthesized from a common intermediate: 3,15-dimethoxycarbonyl-[7]helicene ( 26 ). The conformation of the bridged [7]helicenes (X-ray diffraction) and their 1H-NMR. spectra have been compared to the conformation and 1H-NMR. spectra of [7]helicene and 3,15-dimethyl-[7]helicene ( 10 ). 相似文献
14.
Dr. Deepali Waghray Dr. Gintautas Bagdziunas Jeroen Jacobs Prof. Dr. Luc Van Meervelt Prof. Dr. Juozas Vidas Grazulevicius Prof. Dr. Wim Dehaen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(51):18791-18798
In the present study, we have investigated different strategies for diastereoselective synthesis of thia[n]helicenes. We describe the introduction of different chiral auxiliaries at various positions and investigated their effect in the photocyclization reaction. Different chiral groups were placed at the sterically hindered position of the helical core and their interactions with various solvents and metals like copper were investigated. The use of CuI salts has led to high diastereoselectivity in the photocyclization process and we were successful in obtaining the thia[5]helicene in enantiomerically pure form in good yield. The single diastereomer obtained was characterized by X‐ray crystallography. From the study of the barrier of racemization of these thia[5]helicenes, the stability was found to be comparable to unsubstituted tetrathia[7]helicenes and substituted diazadithia[7]helicenes. This approach provides an easy access to enantiopure helicenes. 相似文献
15.
Long Zhao Ralf I. Kaiser Wenchao Lu Musahid Ahmed Mikhail M. Evseev Eugene K. Bashkirov Valeriy N. Azyazov Christina Tönshoff Florian Reicherter Holger F. Bettinger Alexander M. Mebel 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(28):11430-11434
A representative, low-temperature gas-phase reaction mechanism synthesizing polyacenes via ring annulation exemplified by the formation of pentacene (C22H14) along with its benzo[a]tetracene isomer (C22H14) is unraveled by probing the elementary reaction of the 2-tetracenyl radical (C18H11.) with vinylacetylene (C4H4). The pathway to pentacene—a prototype polyacene and a fundamental molecular building block in graphenes, fullerenes, and carbon nanotubes—is facilitated by a barrierless, vinylacetylene mediated gas-phase process thus disputing conventional hypotheses that synthesis of polycyclic aromatic hydrocarbons (PAHs) solely proceeds at elevated temperatures. This low-temperature pathway can launch isomer-selective routes to aromatic structures through submerged reaction barriers, resonantly stabilized free-radical intermediates, and methodical ring annulation in deep space eventually changing our perception about the chemistry of carbon in our universe. 相似文献
16.
Dr. Prince Ravat 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(12):3957-3967
The most important stereodynamic feature of carbo[n]helicenes is the interconversion of their enantiomers. The Gibbs activation energy (ΔG≠(T)) of this process, which determines the rate of enantiomerization, dictates the configurational stability of [n]helicenes. High values of ΔG≠(T) are required for applications of functional chiral molecules incorporating [n]helicenes or helicene substructures. This minireview provides an overview of the mechanism, recent developments, and factors affecting the enantiomerization of [n]helicenes, which will accelerate the design process of configurationally stable functional chiral molecules based on helicene substructures. Additionally, this minireview addresses the misconception and irregularities in the recent literature on how the terms “racemization” and “enantiomerization” are used as well as how the activation parameters are calculated for [n]helicenes and related compounds. 相似文献
17.
Dr. Paul J. Evans Dr. Jiangkun Ouyang Dr. Ludovic Favereau Dr. Jeanne Crassous Dr. Israel Fernández Dr. Josefina Perles Prof. Dr. Nazario Martín 《Angewandte Chemie (International ed. in English)》2018,57(23):6774-6779
A rigid, inherently chiral bilayer nanographene has been synthesized as both the racemate and enantioenriched M isomer (with 93 % ee) in three steps from established helicenes. This folded nanographene is composed of two hexa‐peri‐hexabenzocoronene layers fused to a [10]helicene, with an interlayer distance of 3.6 Å as determined by X‐ray crystallography. The rigidity of the helicene linker forces the layers to adopt a nearly aligned AA‐stacked conformation, rarely observed in few‐layer graphene. By combining the advantages of nanographenes and helicenes, we have constructed a bilayer system of 30 fused benzene rings that is also chiral, rigid, and remains soluble in common organic solvents. We present this as a molecular model system of bilayer graphene, with properties of interest in a variety of potential applications. 相似文献
18.
Dr. Arseni Borissov Prof. Piotr J. Chmielewski Prof. Carlos J. Gómez García Prof. Tadeusz Lis Prof. Marcin Stępień 《Angewandte Chemie (International ed. in English)》2023,62(38):e202309238
Diradicaloid helicenes constructed formally by non-benzenoid double π-extension of phenanthrene were synthesized by a common strategy involving double electrophilic benzannulation. Steric effects in the second benzannulation step led to considerable structural diversity among the products, yielding a symmetrical dinor[7]helicene 1 and two isomeric unsymmetrical double helicenes 2 and 3 , containing a nor[5]helicene and [4]helicene fragment, respectively, in addition to a common nor[6]helicene motif. Geometries, configurational dynamics, and electronic structure of these helicenes were analyzed using solid-state structures, spectroscopic methods, and computational analyses. The open-shell character of the singlet states of these helicenes increases in the order 3 < 1 < 2 , with strongly varying diradicaloid indexes and singlet–triplet gaps. Compounds 1 – 3 displayed narrow optical gaps of 0.79–1.25 eV, resulting in significant absorption in the near infrared (NIR) region. They also exhibit reversible redox chemistry, each of them yielding stable radical cations, radical anions, and dianions, in some cases possessing intense NIR absorptions extending beyond 2500 nm. 相似文献
19.
The Use of (−)‐Sparteine/Organolithium Reagents for the Enantioselective Lithiation of 7,8‐Dipropyltetrathia[7]helicene: Single and Double Kinetic Resolution Procedures 下载免费PDF全文
Dr. Julien Doulcet Dr. G. Richard Stephenson 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(51):18677-18689
The effect of organolithium reagent (RLi: R=nBu, iPr, sBu, tBu), solvent (diethyl ether, diethyl ether/THF and MTBE), and stoichiometry on the (?)‐sparteine‐mediated silylation of 7,8‐dipropyltetrathia[7]helicene shows that, unusually, substantially more than 0.5 equivalent of RLi (R=iPr, sBu, tBu) and a large excess of (?)‐sparteine (R=nBu, sBu) is often needed to achieve substantial conversions and good ee values. With nBuLi, however, just one equivalent of the organolithium reagent is sufficient to obtain high conversions. Our best results were obtained using the convenient tBuLi/(?)‐sparteine adduct with which the need for a high (?)‐sparteine/RLi ratio can be avoided. Single‐ and double‐kinetic resolution (KR) procedures give enantiopure samples of 2‐trimethylsilyl‐ and 2,13‐di(trimethylsilyl)‐7,8‐dipropyltetrathia[7]helicene and two‐step double‐KR combining (?)‐sparteine/sBuLi and chiral formamides affords the synthetically valuable 2‐formyl‐7,8‐dipropyltetrathia[7]helicene. This is the first use of (?)‐sparteine for the enantioselective lithiation of helicenes and the first report of tBuLi outperforming sBuLi in a (?)‐sparteine‐mediated procedure. 相似文献
20.
Jindřich Nejedlý Dr. Michal Šámal Dr. Jiří Rybáček Miroslava Tobrmanová Dr. Florence Szydlo Dr. Christophe Coudret Maria Neumeier Dr. Jaroslav Vacek Dr. Jana Vacek Chocholoušová Miloš Buděšínský Dr. David Šaman Dr. Lucie Bednárová Dr. Ladislav Sieger Dr. Irena G. Stará Dr. Ivo Starý 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(21):5933-5937
A series of oxahelicenes composed of ortho/meta-annulated benzene/pyridine and 2H-pyran rings were synthesized on the basis of the cobalt(I)-mediated (or rhodium(I)- or nickel(0)-mediated) double, triple, or quadruple [2+2+2] cycloisomerization of branched aromatic hexa-, nona-, or dodecaynes, thus allowing the construction of 6, 9, or 12 rings in a single operation. The use of a flow reactor was found to be beneficial for the multicyclization reactions. The stereogenic centers present in some of the oligoynes steered the helical folding in such a way that the final oxa[9]-, [13]-, [17]- and [19]helicenes were obtained in both enantiomerically and diastereomerically pure form. Specifically, the oxa[19]helicenes beat the current record in the length of a helicene backbone. Single-molecule conductivity was studied by the mechanically controllable break-junction method with a pyridooxa[9]helicene. 相似文献