Perspectives on push–pull chromophores derived from click-type [2 + 2] cycloaddition–retroelectrocyclization reactions of electron-rich alkynes and electron-deficient alkenes

• Michio Yamada

Beilstein J. Org. Chem. 2024, 20, 125–154, doi:10.3762/bjoc.20.13

• may not be apparent at a glance. Nevertheless, comprehensive computational analyses employing the matrix method suggest that the intense long-wavelength CD signal observed for 56 is due to the coupling of individual helicene-to-TCBD electric-transition dipole moments. The emergence of axial chirality

• . The absolute configurations of the axially chiral TCBD and DCNQ derivatives were ascertained by a comparative analysis of the experimental CD spectra against the spectra derived from time-dependent density functional theory (TD-DFT) calculations. The axial chirality was stabilized by the steric

• congestion on the surface of fullerene, with its endurance contingent upon the bulkiness of the substituent incorporated onto the fullerene core. This observation was supported by the absence of axial chirality in molecules where an additional alkyne moiety is intercalated between the C60 core and TCBD or

Aromatic C–H bond functionalization through organocatalyzed asymmetric intermolecular aza-Friedel–Crafts reaction: a recent update

• Anup Biswas

Beilstein J. Org. Chem. 2023, 19, 956–981, doi:10.3762/bjoc.19.72

• aryl moieties. For this purpose, sterically bulky substituents need to be present in the aryl ring attached to the C3 position of the starting indoles. The axial chirality was attributed to ester and phenolic OH groups at the ortho-positions of the aryl ring and an additional phenolic OH functionality

• electrophilic substitution also gave a quaternary aza-stereocenter in the pyrazolone moiety. Axial chirality associated with central chirality in the product structures was influenced by chiral phosphoric acid catalyst P23. To freeze the C–C bond rotation, the pyrazole moiety in 99 required sterically demanding

• . Functionalization of the carbocyclic ring of substituted indoles. Aza-Friedel–Crafts reaction between unprotected imines and aza-heterocycles. Anilines and α-naphthols as potential nucleophiles. Solvent-controlled regioselective aza-Friedel–Crafts reaction. Generating central and axial chirality via aza-Friedel

A new oxidatively stable ligand for the chiral functionalization of amino acids in Ni(II)–Schiff base complexes

• Alena V. Dmitrieva,
• Oleg A. Levitskiy,
• Yuri K. Grishin and
• Tatiana V. Magdesieva

Beilstein J. Org. Chem. 2023, 19, 566–574, doi:10.3762/bjoc.19.41

• ]. Functionalization of the phenyl ring in the benzophenone gives rise to an additional axial chirality (L3), thus improving stereoselectivity observed at the removed stereocenter [24][25]. Replacing N-benzylproline for 2,7-dihydro-1H-azepine (L5) allowed obtaining a new tridentate ligand with chemically stable axial

• chirality which exhibits no racemization under action of strong bases [29]. The chiral N–H-containing rimantadine-based ligand (L6) is highly lipophilic and it was successfully used for the kinetic resolution of unprotected racemic amino acids [30]. The examples mentioned above show that the metal–Schiff

BINOL as a chiral element in mechanically interlocked molecules

• Matthias Krajnc and
• Jochen Niemeyer

Beilstein J. Org. Chem. 2022, 18, 508–523, doi:10.3762/bjoc.18.53

• stereoselective chemosensing. Given the growing importance of mechanically interlocked molecules and the key advantages of the privileged chiral BINOL backbone, we believe that this research area will continue to grow and deliver many useful applications in the future. Keywords: axial chirality; BINOL; catenanes

• chemosensing or in asymmetric catalysis. The selection of suitable stereogenic elements is of great importance [26][27][28]. The most straightforward way to create a chiral rotaxane or catenane is the introduction of classical chiral elements, such molecular parts with axial chirality, point chirality, or

• rotaxanes, the helicity is predetermined by the planar chirality (based on the underlying macrocycle–macrocycle interactions), so that only two diastereoisomers remain for a given BINOL configuration (e.g., (R)-(Rp) and (R)-(Sp) in case of (R)-BINOL). In contrast to the axial chirality of the BINOL unit

Recent advances in the asymmetric phosphoric acid-catalyzed synthesis of axially chiral compounds

• Alemayehu Gashaw Woldegiorgis and
• Xufeng Lin

Beilstein J. Org. Chem. 2021, 17, 2729–2764, doi:10.3762/bjoc.17.185

• of a wide range of axially chiral biaryls, heterobiaryls, vinylarenes, N-arylamines, spiranes, and allenes with high efficiency and excellent stereoselectivity. Keywords: allenes; atropisomerism; axial chirality; chiral phosphoric acid; heterobiaryls; spiranes; Introduction Axial chirality is one

• construction of axial chirality [7][8][9][10][11][12][13][14]. Axially chiral biaryl and heterobiaryl units are widely used as basic building blocks for chiral ligands [14], chiral catalysts [14][15][16][17] (Figure 1), various natural products, drugs and bioactive molecules [18][19], pharmaceutical agents [20

• -catalyzed enantioselective transformations [9][14][22][23]. Axial chirality is also found in chiral stationary phases for enantioselective separation, dopants in liquid-crystalline materials, chiroptical molecular switches, microporous soluble polymers, and interlocked nanotubes (Figure 3) [24]. In addition

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

• repulsion of the terminal aromatic nuclei. The steric strain releases by adopting either the P- or M-helix configuration. The helically extended π-conjugated system, axial chirality and associated with these structural peculiarities unique optical and electronic properties of helicenes have attracted

A cyclopeptide and three oligomycin-class polyketides produced by an underexplored actinomycete of the genus Pseudosporangium

• Shun Saito,
• Kota Atsumi,
• Tao Zhou,
• Keisuke Fukaya,
• Daisuke Urabe,
• Naoya Oku,
• Md. Rokon Ul Karim,
• Hisayuki Komaki and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2020, 16, 1100–1110, doi:10.3762/bjoc.16.97

• -acetyl-ʟ-Tyr-ʟ-Pro-ʟ-Trp, was determined by a combination of spectroscopic analyses, chemical derivatization, ECD calculation, and DFT-based theoretical chemical shift calculation, revealing the presence of an (Sa)-axial chirality around the biaryl bond. Compounds 2–4 lacked hydroxylation on the side

• comparison of experimental and simulated ECD spectra [26][27]. Quite interestingly, the DFT calculation suggested that 1a and 1b would possess the opposite axial chirality around the biaryl bond between C-6 and C-7'': Ra for 1a and Sa for 1b as dominant atropisomers (Figure 4). This conformational difference

• pseudosporamicins A–C (2–4). COSY, key HMBC and ROESY correlations of pseudosporamide (1). 1H NMR ΔδS−R values for PGME amides 5a and 5b obtained from compound 1. The opposite axial chirality around the biaryl C-6–C-7'' bond influenced by the C-2 configuration in compound 1. 3D structures 1a-1 and 1b-1 are the most

Catalytic asymmetric oxo-Diels–Alder reactions with chiral atropisomeric biphenyl diols

• Chi-Tung Yeung,
• Wesley Ting Kwok Chan,
• Wai-Sum Lo,
• Ga-Lai Law and
• Wing-Tak Wong

Beilstein J. Org. Chem. 2019, 15, 955–962, doi:10.3762/bjoc.15.92

• : asymmetric organocatalysis; axial chirality; biaryls; hydrogen bond; oxo-Diels–Alder reaction; Introduction The Diels–Alder (DA) reaction is a useful and easy-to-perform method for the synthesis of six-membered rings through the direct formation of C–C bonds between a diene and a dienophile (a substituted

• supramolecular helices or dimers through intermolecular hydrogen bonding of two axially chiral biphenyl hybrid diols (1 and 2 in Scheme 1) which contain point chirality at the side arms and axial chirality at the biphenyl backbone [37]. We envisage the structural similarity and the ability of our scaffold to

• , entries 5 and 6). It should be noted that the absolution configuration of the catalytic product seems to be determined by the axial chirality (P or M) of 5 rather than its point chirality at the side arms (both have the same R-chirality) [40]. The axial chirality of other catalysts have been reported

A diastereoselective approach to axially chiral biaryls via electrochemically enabled cyclization cascade

• Hong Yan,
• Zhong-Yi Mao,
• Zhong-Wei Hou,
• Jinshuai Song and
• Hai-Chao Xu

Beilstein J. Org. Chem. 2019, 15, 795–800, doi:10.3762/bjoc.15.76

• the biaryls with good to excellent central-to-axial chirality transfer. Keywords: axial chirality; biaryl; electrochemistry; oxidation; radical; Introduction Axially chiral biaryls are prevalent in natural products, bioactive molecules and organocatalysts [1][2]. Among the many methods that have

• been developed for the synthesis of chiral biaryls [3][4][5][6][7][8][9][10], reactions that take avantage of the central-to-axial chirality transfer have been less explored [11][12][13][14]. In addition, an antroposelective synthesis of imidazopyridine-based biaryls has not been reported. Nitrogen

• imidazopyridine-containing biaryls via central-to-axial chirality transfer (Scheme 1). Results and Discussion The substituents on the phenyl ring (R1) and at the propargylic position (R2) of carbamate 2 were varied to study their effects on the diastereoselectivity (Table 1). The electrolysis was conducted under

Synthesis of indole–cycloalkyl[b]pyridine hybrids via a four-component six-step tandem process

• Muthumani Muthu,
• Rakkappan Vishnu Priya,
• Abdulrahman I. Almansour,
• Raju Suresh Kumar and
• Raju Ranjith Kumar

Beilstein J. Org. Chem. 2018, 14, 2907–2915, doi:10.3762/bjoc.14.269

• –cyclododeca[b]pyridine-3-carbonitriles 7 with ortho/ortho-para/ortho-meta substituted phenyl ring at C-4, exhibited axial chirality. For instance, in the case of 7f with p-Cl substituted phenyl ring at C-4, the 5- and 14-CH2 protons appeared as triplets at 2.56 and 3.01 ppm, respectively. However, in 7l

• [b]pyridine-3-carbonitrile hybrid heterocycles 7 with an ortho/ortho-para/ortho-meta substituted phenyl ring at C-4 may be attributed to the axial chirality induced in these molecules due to the restricted rotation of the C–C single bond. The steric hindrance exerted between the nitrile group at C-3

• and the ortho/ortho-para/ortho-meta substitution in the phenyl ring at C-4 restricts the free rotation of the C-4–phenyl C–C single bond thereby inducing axial chirality in these molecules (representative examples, Figure 2). Interestingly in some cases this reaction afforded the unaromatized indole

Some mechanistic aspects regarding the Suzuki–Miyaura reaction between selected ortho-substituted phenylboronic acids and 3,4,5-tribromo-2,6-dimethylpyridine

• Piotr Pomarański,
• Piotr Roszkowski,
• Jan K. Maurin,
• Armand Budzianowski and
• Zbigniew Czarnocki

Beilstein J. Org. Chem. 2018, 14, 2384–2393, doi:10.3762/bjoc.14.214

• , Poland 10.3762/bjoc.14.214 Abstract Background: Atropisomers are very interesting stereoisomers having axial chirality resulting from restricted rotation around single bonds and are found in various classes of compounds. ortho-Substituted arylpyridines are an important group of them. A regio- and

• , Tanaka presented an atropselective synthesis of axially chiral all-benzenoid biaryls by gold-catalysed intramolecular hydroarylation of alkynones to give the desired atropisomeric product with a good ee value of 70% [26]. Conventional approaches to the synthesis of biaryl compounds having axial chirality

Design, synthesis and structure of novel G-2 melamine-based dendrimers incorporating 4-(n-octyloxy)aniline as a peripheral unit

• Cristina Morar,
• Pedro Lameiras,
• Attila Bende,
• Gabriel Katona,
• Emese Gál and
• Mircea Darabantu

Beilstein J. Org. Chem. 2018, 14, 1704–1722, doi:10.3762/bjoc.14.145

• solution, for example, asymmetric vs propeller (C3-symmetric) [30][36][45][46], “dendritic choreography” [47], “open-gates closed-gates” frontier rotamerism [31] and “in out” axial chirality [33]. In addition, in the targeted G-2 dendrimers (Figure 1), different connections of branches around the core

A survey of chiral hypervalent iodine reagents in asymmetric synthesis

• Soumen Ghosh,
• Suman Pradhan and
• Indranil Chatterjee

Beilstein J. Org. Chem. 2018, 14, 1244–1262, doi:10.3762/bjoc.14.107

• introduction of axial chirality through the iodoarene backbone. A series of chiral iodine reagents are documented below (Scheme 1). In many cases chiral I(I) reagents get oxidized in situ to the hypervalent I(III) reagents and/or these chiral I(III)/I(V) reagents are used in a catalytic amount in the presence

From dipivaloylketene to tetraoxaadamantanes

• Gert Kollenz and
• Curt Wentrup

Beilstein J. Org. Chem. 2018, 14, 1–10, doi:10.3762/bjoc.14.1

• exhibit axial chirality [21], as has been demonstrated by 1H NMR spectroscopy using the optically active shift reagent Eu(hfc)3 [19]. The enantiomers of the dicarboxylic acid 11 have been separated by flash chromatography of their diastereomeric salts with 1-phenethylamine, and the structures of the acids

• [29]. It should be noted that both the bisdioxines [19] and the tetraoxaadamantanes [29] exhibit axial chirality as confirmed by 1H NMR spectroscopy with the Eu(hfc)3 chiral shift reagent. Bisdioxine oxime and hydrazine derivatives 26 and 27 (Scheme 8) are formed from 3 at room temperature without the

Bifunctional organocatalysts for the asymmetric synthesis of axially chiral benzamides

• Ryota Miyaji,
• Yuuki Wada,
• Akira Matsumoto,
• Keisuke Asano and
• Seijiro Matsubara

Beilstein J. Org. Chem. 2017, 13, 1518–1523, doi:10.3762/bjoc.13.151

• . Moderate to good enantioselectivities were afforded with a range of benzamide substrates. Mechanistic investigations were also carried out. Keywords: axial chirality; benzamide; bifunctional organocatalyst; molecular conformation; multipoint recognition; Introduction Bifunctional organocatalysts have

• resolution [42][43][44][45][46][47], desymmetrization [48][49][50][51][52][53][54], de novo annulation [55][56][57][58][59][60][61], and point-to-axial chirality transfer [58][59] (for reviews, see references [31][62][63]), motivated us to expand on the utility of this class of small-molecule catalysts. We

• axial chirality [36][37]. Thus, we assumed that this method could be further applied to the enantioselective synthesis of a range of axially chiral compounds. In this study, we present the enantioselective synthesis of 3-hydroxybenzamides via aromatic electrophilic bromination [28][29]. The 3

Varioloid A, a new indolyl-6,10b-dihydro-5aH-[1]benzofuro[2,3-b]indole derivative from the marine alga-derived endophytic fungus Paecilomyces variotii EN-291

• Peng Zhang,
• Xiao-Ming Li,
• Xin-Xin Mao,
• Attila Mándi,
• Tibor Kurtán and
• Bin-Gui Wang

Beilstein J. Org. Chem. 2016, 12, 2012–2018, doi:10.3762/bjoc.12.188

• Cotton effects (CEs) had the same sign for conformer A and B, while the lower-wavelength (<250 nm) CEs were significantly different. The hindered rotation along the biaryl linkage may have implied an additional stereogenic element, which would have enabled atropodiastereomers with axial chirality. In

• order to explore the possibility of axial chirality, torsional angle scans were performed on the lowest-energy M (conformer A) and P (conformer B) helicity gas-phase conformers or atropodiastereomers. Rotational energy barriers between the two isomers were estimated to be ca. 35–42 kJ/mol for TS1 (ωC12

• showed that there is no axial chirality in 1, and equilibrating conformers with M and P helicity are present in solution as obtained in the conformational analysis. The Boltzmann-weighted ECD spectra calculated for both the gas-phase and the solvent model conformers of (2R,3R)-1 at B3LYP/TZVP, BH&HLYP

Stereodynamic tetrahydrobiisoindole “NU-BIPHEP(O)”s: functionalization, rotational barriers and non-covalent interactions

• Golo Storch,
• Sebastian Pallmann,
• Frank Rominger and
• Oliver Trapp

Beilstein J. Org. Chem. 2016, 12, 1453–1458, doi:10.3762/bjoc.12.141

• ][6], palladium [7][8], platinum [9][10] and gold [11][12][13] in combination with chiral co-ligands or counter ions that are used after alignment of the ligand’s axial chirality. One major advantage of stereodynamic ligands is that there is no need for separate preparation of one ligand enantiomer as

Recent advances in copper-catalyzed asymmetric coupling reactions

• Fengtao Zhou and
• Qian Cai

Beilstein J. Org. Chem. 2015, 11, 2600–2615, doi:10.3762/bjoc.11.280

• into the substrates, has emerged as a powerful tool for constructing natural products and useful ligands with axial chirality. Based on asymmetric desymmetrization and kinetic resolution strategies, a series of efficient copper-catalyzed systems have been developed for the formation of C–C, C–N, C–O

Chiroptical properties of 1,3-diphenylallene-anchored tetrathiafulvalene and its polymer synthesis

• Masashi Hasegawa,
• Junta Endo,
• Seiya Iwata,
• Toshiaki Shimasaki and
• Yasuhiro Mazaki

Beilstein J. Org. Chem. 2015, 11, 972–979, doi:10.3762/bjoc.11.109

• carried out by direct C–H activation of the TTF unit, and the chiroptical properties of the resulting polymer were also investigated. Keywords: allene; axial chirality; chiroptical properties; redox; tetrathiafulvalene; Introduction Recently, there has been a growing interest in chiral π-conjugated

P(O)R₂-directed Pd-catalyzed C–H functionalization of biaryl derivatives to synthesize chiral phosphorous ligands

• Rong-Bin Hu,
• Hong-Li Wang,
• Hong-Yu Zhang,
• Heng Zhang,
• Yan-Na Ma and
• Shang-dong Yang

Beilstein J. Org. Chem. 2014, 10, 2071–2076, doi:10.3762/bjoc.10.215

• reported operation, the substrates of biaryl derivatives that contained phosphate with axial chirality were obtained in high yields using the Suzuki–Miyaura coupling reaction with the assistance of this versatile chiral ligand [31][32][33][34]. We used substituted naphthylboronic acid or ortho-substituted

• -phenylboronic acid to synthesize the corresponding substituted binaphthyl or phenyl-naphthyl skeleton substrates with axial chirality. To maintain the axial chirality within the substrates, a steric hindrance effect at the ortho position of phenylboronic acids was required, rendering the non-ortho substituted

Homolytic substitution at phosphorus for C–P bond formation in organic synthesis

• Hideki Yorimitsu

Beilstein J. Org. Chem. 2013, 9, 1269–1277, doi:10.3762/bjoc.9.143

• phosphorus. Plausible mechanism of radical phosphination (Si = (Me3Si)3Si). Stereoselective phosphination leading to (S,S)-aminophosphine derivative. Phosphination with retention of axial chirality. Chemodivergent phosphination. Bis(phosphoryl)-bridged biphenyls by radical phosphination. Bis(phosphoryl

Design and synthesis of quasi-diastereomeric molecules with unchanging central, regenerating axial and switchable helical chirality via cleavage and formation of Ni(II)–O and Ni(II)–N coordination bonds

• Vadim A. Soloshonok,
• José Luis Aceña,
• Hisanori Ueki and
• Jianlin Han

Beilstein J. Org. Chem. 2012, 8, 1920–1928, doi:10.3762/bjoc.8.223

• *) and (Ra*,Ph*,Rc*) occurs by intramolecular trans-coordination of Ni–NH and Ni–O bonds providing a basis for a chiral switch model. Keywords: axial chirality; central chirality; chiral switches; coordination bonds; functional materials; helical chirality; modular structural design; molecular devices

• concurrent and unidirectional motion of arms ED and AB is expected to have the following desired stereochemical consequences: Thus, the axial chirality on the arm CDE in 5 will disappear with simultaneous generation of a new chiral axis on the arm CBA in 6, of the same stereochemical sense. Next, this

• envisioned mode of transcoordination must proceed also with a loss and regeneration of helical chirality, but, in contrast to the loss/regeneration of axial chirality, with the inversion of the stereochemical sense, providing quasi-diastereomeric relationships between complexes 5 and 6 [26]. As one can

The interplay of configuration and conformation in helical perylenequinones: Insights from chirality induction in liquid crystals and calculations

• Elisa Frezza,
• Silvia Pieraccini,
• Stefania Mazzini,
• Alberta Ferrarini and
• Gian Piero Spada

Beilstein J. Org. Chem. 2012, 8, 155–163, doi:10.3762/bjoc.8.16

• essentially determined by the axial chirality (helicity) of the core of the perylenequinones. Keywords: chirality; conformational analysis; DFT calculations; helical twisting power; nematic liquid crystals; Introduction The phenomenon of chiral induction in nematic mesophases has been known for a long time

• the determination of the absolute configuration [2][3][5][6][12][13][14][15][16][17][18][19][20][21][22][23][24]. In fact, this technique has been fruitfully applied to different classes of systems, possessing either stereogenic centers or axial chirality. In this work, chirality induction in liquid

• ) [27], shown in Figure 1. They have the same stereochemical features: Two bulky methoxy groups or a strained seven-membered ring in positions 6 and 7, two side chains in positions 1 and 12 and a nonplanar helical shape. The helicity generates axial chirality, which, when associated with the presence of

Bromine–lithium exchange: An efficient tool in the modular construction of biaryl ligands

• Laurence Bonnafoux,
• Frédéric R. Leroux and
• Françoise Colobert

Beilstein J. Org. Chem. 2011, 7, 1278–1287, doi:10.3762/bjoc.7.148

• . Catalytic studies as well as the control of biaryl axial chirality are currently underway and will be reported in due course. Modular synthesis of bis(diarylphosphino)-, bis(dialkylphosphino)- and dialkyl(diaryl)phosphinobiphenyls as well as monophosphinobiphenyls by means of polar organometallic chemistry

Cationic gold(I) axially chiral biaryl bisphosphine complex-catalyzed atropselective synthesis of heterobiaryls

• Tetsuro Shibuya,
• Kyosuke Nakamura and
• Ken Tanaka

Beilstein J. Org. Chem. 2011, 7, 944–950, doi:10.3762/bjoc.7.105

• complex catalyzes the atropselective intramolecular hydroarylation of alkynes leading to enantioenriched axially chiral 4-aryl-2-quinolinones and 4-arylcoumarins with up to 61% ee. Keywords: asymmetric catalysis; axial chirality; gold; heterobiaryls; hydroarylation; Introduction Atropselective biaryl