Construction of hexabenzocoronene-based chiral nanographenes

• Ranran Li,
• Di Wang,
• Shengtao Li and
• Peng An

Beilstein J. Org. Chem. 2023, 19, 736–751, doi:10.3762/bjoc.19.54

• [20][21][22][23][24]. Currently, there is a great interest in the introduction of chirality into large conjugated polyaromatics to obtain chiral NGs with chiroptical properties. Among these chiral NGs, helicenes represent the dominant chiral compounds by virtue of their inherent helical chirality [25

• seco-HBC, which gives a helical chiral structure. Based on this incomplete cyclizing strategy, types of seco-HBC-based chiral NGs were synthesized. Shown in Scheme 2 are the [5]helicenes that were synthesized from the corresponding hexaarylbenzenes as incompletely cyclized products during the Scholl

• octagon-containing carbo[5]helicene was isolated in a 61% yield, which can be further transformed into other chiral hydrocarbon analogues 12 and 13 [35]. Chiral resolution of these helicenes was accomplished by chiral high-performance liquid chromatography (HPLC) and the isomerization barriers were

Thiophene/selenophene-based S-shaped double helicenes: regioselective synthesis and structures

• Mengjie Wang,
• Lanping Dang,
• Wan Xu,
• Zhiying Ma,
• Liuliu Shao,
• Guangxia Wang,
• Chunli Li and
• Hua Wang

Beilstein J. Org. Chem. 2022, 18, 809–817, doi:10.3762/bjoc.18.81

• (trimethylsilanyl)diseleno[2,3-b:3′,2′-d]thiophene ((TMS)2-bb-DST), and 2,5-di(trimethylsilanyl)diseleno[2,3-b:3′,2′-d] selenophene ((TMS)2-bb-DSS) were used as starting materials to synthesize three S-shaped double helicenes (i.e., DH-1, DH-2, and DH-3) through monobromination, formylation, the Wittig reaction

• ; selenophene; thiophene; Introduction Given their esthetically pleasing helical structures, inherent helical chirality, and extended π-conjugation, helicenes have attracted extensive research attention. Helicenes are generally divided into carbohelicenes and heterohelicenes. The rapid development of

• thiahelicene, a class of typical heterohelicenes, has led to the preparation of symmetric thiophene-based [5]-, [7]-, [9]-, and [11]helicenes [9][10][11][12][13][14][15][16], unsymmetric thiophene-based [7]helicenes [17], and thiophene-based double helicenes with spiro-silicon atoms [18], “saddle” formed 8π

Synthesis, structural characterization, and optical properties of benzo[f]naphtho[2,3-b]phosphoindoles

• Mio Matsumura,
• Takahiro Teramoto,
• Masato Kawakubo,
• Masatoshi Kawahata,
• Yuki Murata,
• Kentaro Yamaguchi,
• Masanobu Uchiyama and
• Shuji Yasuike

Beilstein J. Org. Chem. 2021, 17, 671–677, doi:10.3762/bjoc.17.56

• is known that λmax of [n]helicenes generally has a shorter wavelength than for the corresponding linear poly(acene)s [25]. The λmax of benzo[e]naphtho[2,1-b]phosphindole (A), 358 nm [16], is the same as that of parent 2. In contrast, the corresponding oxide B has a λmax wavelength that is

Helicene synthesis by Brønsted acid-catalyzed cycloaromatization in HFIP [(CF₃)₂CHOH]

• Takeshi Fujita,
• Noriaki Shoji,
• Nao Yoshikawa and
• Junji Ichikawa

Beilstein J. Org. Chem. 2021, 17, 396–403, doi:10.3762/bjoc.17.35

• gram-scale syntheses of higher-order helicenes, double helical helicenes, and heterohelicenes. Keywords: acid; catalyst; cyclization; fluoroalcohol; helicenes; Introduction Helicenes are a class of polycyclic aromatic hydrocarbons (PAH) that consist of ortho-fused aromatic rings arranged in a helical

• manner [1][2][3][4][5][6]. Since helicenes possess chirality derived from their helical structure, optically active helicenes and their derivatives exhibit characteristic properties, such as huge optical rotation [7], nonlinear optical effects [8][9][10], and circularly polarized light emission [11

• ], which are rarely found in planar aromatic hydrocarbons (e.g., acenes and phenacenes). Therefore, the wide breadth of applications of helicenes as organic optical materials make them interesting synthetic targets. Although several methods for the synthesis of helicenes have been reported, there are still

Synthesis, crystal structures and properties of carbazole-based [6]helicenes fused with an azine ring

• Daria I. Tonkoglazova,
• Anna V. Gulevskaya,
• Konstantin A. Chistyakov and
• Olga I. Askalepova

Beilstein J. Org. Chem. 2021, 17, 11–21, doi:10.3762/bjoc.17.2

• . Kovalevskaya Str., 22, Yekaterinburg 620219, Russian Federation 10.3762/bjoc.17.2 Abstract Novel carbazole-based [6]helicenes fused with an azine ring (pyridine, pyrazine or quinoxaline) have been prepared through a five-step synthetic sequence in good overall yields. Commercially available 2,3-dihaloazines

• were used as starting materials. To discern the effect of merging an azine moiety within a helical skeleton, the X-ray structures, UV–vis absorption and fluorescence spectra of the helicenes were investigated and compared to that of the parent carbazole-based [6]helicene (7H-phenanthro[3,4-c]carbazole

• ). Keywords: azine-fused helicenes; carbazole-based [6]helicenes; helical structures; Introduction [n]Helicenes are polycyclic aromatic molecules with nonplanar screw-shaped helical skeletons formed by n-ortho-fused benzene or other aromatic rings. Their helical structure is a consequence of the steric

Bipyrrole boomerangs via Pd-mediated tandem cyclization–oxygenation. Controlling reaction selectivity and electronic properties

• Liliia Moshniaha,
• Marika Żyła-Karwowska,
• Joanna Cybińska,
• Piotr J. Chmielewski,
• Ludovic Favereau and
• Marcin Stępień

Beilstein J. Org. Chem. 2020, 16, 895–903, doi:10.3762/bjoc.16.81

• measurements show that helicene-like boomerangs may be usable as circularly polarized luminescent materials. Keywords: donor–acceptor systems; double C–H bond activation; helicenes; pyrroles; Introduction Nanographenes and other polycyclic aromatics as well as their heterocyclic analogues are typically

Regioselective synthesis of chiral dimethyl-bis(ethylenedithio)tetrathiafulvalene sulfones

• Flavia Pop and
• Narcis Avarvari

Beilstein J. Org. Chem. 2015, 11, 1105–1111, doi:10.3762/bjoc.11.124

• previously observed only in bismuth wires and carbon nanotubes [13]. Another interesting research area is the redox modulation of the chiroptical properties described in derivatives such as TTF-allenes [14], TTF-helicenes [15], or TTF-paracyclophanes [16]. Thus, to address the different opportunities offered

A facile synthesis of functionalized 7,8-diaza[5]helicenes through an oxidative ring-closure of 1,1’-binaphthalene-2,2’-diamines (BINAMs)

• Youhei Takeda,
• Masato Okazaki,
• Yoshiaki Maruoka and
• Satoshi Minakata

Beilstein J. Org. Chem. 2015, 11, 9–15, doi:10.3762/bjoc.11.2

• , Yamadaoka 2-1, Suita, Osaka 565-0871, Japan 10.3762/bjoc.11.2 Abstract A facile and moderately functional-group-tolerant synthetic method for the preparation of 7,8-diaza[5]helicenes has been developed. It comprises of an oxidative ring-closing process of 1,1’-binaphthalene-2,2’-diamine (BINAM) derivatives

• with a chlorine-containing oxidant (t-BuOCl) in the presence of a base (2,6-lutidine). In addition the basic physicochemical properties of newly synthesized compounds have been investigated. Keywords: aromatic amines; azahelicenes; cinnolines; halogen; oxidation; Introduction Helicenes, ortho-fused

• chirality [2][3][4][5][6][7][8][9][10][11]. In fact, helicenes have been finding more and more potential applications such as optoelectronic materials, asymmetric catalysts, and chemosensors [9]. Therefore, the development of synthetic methods for the preparation of helicenes which are difficult to access

Continuous flow photocyclization of stilbenes – scalable synthesis of functionalized phenanthrenes and helicenes

• Quentin Lefebvre,
• Marc Jentsch and
• Magnus Rueping

Beilstein J. Org. Chem. 2013, 9, 1883–1890, doi:10.3762/bjoc.9.221

• backbone functionalized phenanthrenes and helicenes of various sizes in good yields. Keywords: continuous-flow reactor; flow chemistry; helicenes; light-driven cyclization reaction; photocyclization; stilbenes; Introduction Phenanthrenes are versatile intermediates toward polycyclic aromatic hydrocarbons

• which are relevant for materials sciences, as well as toward helicenes, an intriguing class of molecules which show remarkable chiroptical properties due to their helical pitch. The rapidly expanding field of application of helicene-like molecules in materials sciences and optics demands the development

• [9][10][11][12]. Much effort has devoted to the development of alternative pathways toward helicenes, but most approaches require lengthy syntheses of the precursors [13][14][15]. It should be noted that an elegant semi-one-pot procedure for the synthesis of phenanthrenes from styrenes and benzene

Chiral amplification in a cyanobiphenyl nematic liquid crystal doped with helicene-like derivatives

• Alberta Ferrarini,
• Silvia Pieraccini,
• Stefano Masiero and
• Gian Piero Spada

Beilstein J. Org. Chem. 2009, 5, No. 50, doi:10.3762/bjoc.5.50

• sensitivity to small changes in structure and environment is more often observed. This uniformity of behavior was observed for the helicenes investigated; in penta- and hexa- and carbo- and hetero-helicenes, the relationship between the molecular stereochemical descriptor and the cholesteric handedness was

• verified and interpreted [51]: (P)-helicenes induce (P)-cholesterics in all the cases investigated. In this paper, we focus on a new series of helicene-like molecules of known absolute configuration (Figure 2). We have integrated cholesteric pitch measurements with geometry optimization by DFT calculations

• bisquinones 1–5 and of dihydro- (and tetrahydro-) [4]helicene quinones 6–8 has been described by Carreño, Urbano and coworkers [52][53][54][55][56][57]. The twisting powers of the helicenes under investigation measured in the nematic solvent E7 are reported in Table 1. We can see that all compounds possessing