Complexation of 2,6-helic[6]arene and its derivatives with 1,1′-dimethyl-4,4′-bipyridinium salts and protonated 4,4'-bipyridinium salts: an acid–base controllable complexation

• Jing Li,
• Qiang Shi,
• Ying Han and
• Chuan-Feng Chen

Beilstein J. Org. Chem. 2019, 15, 1795–1804, doi:10.3762/bjoc.15.173

• 10.3762/bjoc.15.173 Abstract 2,6-Helic[6]arene and its derivatives were synthesized, and their complexation with 1,1′-dimethyl-4,4′-bipyridinium and protonated 4,4'-bipyridinium salts were investigated in detail. It was found that the helic[6]arene and its derivatives could all form 1:1 complexes with

• both 1,1′-dimethyl-4,4'-bipyridinium salts and protonated 4,4'-bipyridinium salts in solution and in the solid state. Especially, the helic[6]arene and its derivatives containing 2-hydroxyethoxy or 2-methoxyethoxy groups exhibited stronger complexation with the guests than the other helic[6]arene

• with larger counteranions of the guests and in less polar solvents. Furthermore, the switchable complexation between the helic[6]arene and protonated 4,4'-bipyridinium salt could be efficiently controlled by acids and bases. Keywords: 4,4'-bipyridinium salts; complexation; helic[6]arene; hydrogen bond

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

• Gagandeep Kour Reen,
• Ashok Kumar and
• Pratibha Sharma

Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165

Synthesis, enantioseparation and photophysical properties of planar-chiral pillar[5]arene derivatives bearing fluorophore fragments

• Guojuan Li,
• Chunying Fan,
• Guo Cheng,
• Wanhua Wu and
• Cheng Yang

Beilstein J. Org. Chem. 2019, 15, 1601–1611, doi:10.3762/bjoc.15.164

• Guojuan Li Chunying Fan Guo Cheng Wanhua Wu Cheng Yang Key Laboratory of Green Chemistry & Technology, College of Chemistry and Healthy Food Evaluation Research Center, Sichuan University, 29 Wangjiang Road, Chengdu, 610064, P. R. China 10.3762/bjoc.15.164 Abstract Planar chiral pillar[5]arene

• derivatives (P5A-DPA and P5A-Py) bearing bulky fluorophores were obtained in high yield by click reaction. The photophysical properties of both compounds were investigated in detail. P5A-DPA with two 9,10-diphenylanthracene (DPA) pigments grafted on the pillar[5]arene showed a high fluorescence quantum yield

• of 89.5%. This is comparable to the monomer DPA-6, while P5A-Py with two perylene (Py) pigments grafted on the pillar[5]arene showed a significantly reduced quantum yield of 46.4% vs 78.2% for the monomer Py-6. The oxygen-through-annulus rotation of the phenolic units was inhibited for both compounds

Different reactivity of phosphorylallenes under the action of Brønsted or Lewis acids: a crucial role of involvement of the P=O group in intra- or intermolecular interactions at the formation of cationic intermediates

• Stanislav V. Lozovskiy,
• Alexander Yu. Ivanov and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2019, 15, 1491–1504, doi:10.3762/bjoc.15.151

• 8–11a (Table 2). The presence of the (MeO)2P=O group in the structures of reaction products makes them more soluble in organic solvents and easy to isolate in preparative reactions. Depending on the structure of the starting arene, allene 1a gave two kinds of reaction products, E-/Z-alkenes 11 and

• equivalent of AlCl3 is coordinated to the central atom of the allene system of the complex 13 and gives intermediate 16. The latter, in the absence of nucleophiles (arene molecules), undergoes deprotonation from the methyl group affording butadiene 14. Hydrolysis of the latter resulted in compounds Z-9 and E

• -10a. Whereas, in the presence of an arene, cation 16 reacts with it leading to species 17. The latter can be protonated with the formation of cation 18. This species may react in two different ways. The first option is it could lead to alkene 19 and finally to compounds 11 upon methanolysis of the

2,3-Dibutoxynaphthalene-based tetralactam macrocycles for recognizing precious metal chloride complexes

• Li-Li Wang,
• Yi-Kuan Tu,
• Huan Yao and
• Wei Jiang

Beilstein J. Org. Chem. 2019, 15, 1460–1467, doi:10.3762/bjoc.15.146

• bonds with guests, constituting the main driving forces for molecular recognition. This class of macrocycles, in particular the ones with single arene as sidewalls, have found wide applications in diverse fields: Leigh and co-workers reported many interlocked structures and molecular machines with

• interesting new binding properties. During the last six years, our group have developed a series of naphthol-based macrocyclic receptors [24][25][26][27][28][29]. Of them, oxatub[4]arene [30][31] and zorb[4]arene [32][33] show multiple conformations due to the flipping of naphthalenes and thus resulted in a

• timescale. H3 is diastereotopic and could be split when the conformational interconversion is slow on the NMR timescale, as observed for oxatub[4]arene [30] and zorb[4]arene [32]. When lowering the temperature to 223 K, H3 of 1 was split to two peaks while other peaks become broadened (Figure 1b). This

Complexation of a guanidinium-modified calixarene with diverse dyes and investigation of the corresponding photophysical response

• Yu-Ying Wang,
• Yong Kong,
• Zhe Zheng,
• Wen-Chao Geng,
• Zi-Yi Zhao,
• Hongwei Sun and
• Dong-Sheng Guo

Beilstein J. Org. Chem. 2019, 15, 1394–1406, doi:10.3762/bjoc.15.139

• 300071, P. R. China Research Institute of Petroleum Engineering, Sinopec, Beijing 100101, P. R. China 10.3762/bjoc.15.139 Abstract We herein describe the comprehensive investigation of the complexation behavior of a guanidinium-modified calix[5]arene pentaisohexyl ether (GC5A) with a variety of typical

• fluorescent IDA with guanidinium-modified calix[5]arene pentaisohexyl ether (GC5A) and fluorescein (Fl) as the reporter pair [26]. The ultrasensitive detection is feasible for diagnosing ovarian and other gynecologic cancers at their early stages. Also, we proposed a nanoplatform where the fluorescence and

• photoactivity of photosensitizers (PSs) were annihilated by the complexation of guanidinium-modified calix[5]arene pentadodecyl ether while reactivated by adenosine triphosphate (a cancer biomarker) displacement. This novel supramolecular phototheranostics strategy realized both tumor-selective imaging and

Efficient resolution of racemic crown-shaped cyclotriveratrylene derivatives and isolation and characterization of the intermediate saddle isomer

• Sven Götz,
• Andreas Schneider and
• Arne Lützen

Beilstein J. Org. Chem. 2019, 15, 1339–1346, doi:10.3762/bjoc.15.133

• . Isolation of the product was then possible through repeated column chromatography. Similarly, the same group was also able to isolate the saddle stereoisomer of a chiral nonamethoxy-substituted CTV in which every arene unit carries three additional substituents through HPLC on a chiral stationary phase [27

Host–guest interactions between p-sulfonatocalix[4]arene and p-sulfonatothiacalix[4]arene and group IA, IIA and f-block metal cations: a DFT/SMD study

• Valya K. Nikolova,
• Cristina V. Kirkova,
• Silvia E. Angelova and
• Todor M. Dudev

Beilstein J. Org. Chem. 2019, 15, 1321–1330, doi:10.3762/bjoc.15.131

• .15.131 Abstract The molecular recognition in aqueous solution is extremely important because most biological processes occur in aqueous solution. Water-soluble members of the calix[n]arene family (e.g., p-sulfonato substituted) can serve as model systems for studying the nature and manner of interactions

• between biological receptors and small ions. The complex formation behavior of water-soluble p-sulfonatocalix[4]arene and thiacalix[4]arene and group IA, IIA and f-block metal cations has been investigated computationally by means of density functional theory computations in the gas phase and in aqueous

• cations (La3+) a supramolecular approach with explicit solvent treatment has been applied in the study of the effect of metal hydration on the complexation process. The La3+ binding to the p-sulfonatocalix[4]arene host molecule (now in the metal’s second coordination shell) is still exergonic as evidenced

N-doped carbon dots covalently functionalized with pillar[5]arenes for Fe³⁺ sensing

• Jia Gao,
• Ming-Xue Wu,
• Dihua Dai,
• Zhi Cai,
• Yue Wang,
• Wenhui Fang,
• Yan Wang and
• Ying-Wei Yang

Beilstein J. Org. Chem. 2019, 15, 1262–1267, doi:10.3762/bjoc.15.123

• Engineering, Wuhan University of Science and Technology, Wuhan 430081, P. R. China 10.3762/bjoc.15.123 Abstract Fluorescent N-doped carbon dots (CN-dots) covalently functionalized with carboxylatopillar[5]arene (CP[5]), namely CCDs, have been prepared the first time. Compared with CN-dots without pillarene

• , symmetrical structures, superior host–guest properties, supramolecular assembly characteristics, and versatile functionalities [11][15][16]. Carboxylatopillar[5]arene (CP[5]) is one of the most popular functional pillarenes that has been exploited in many research areas, especially in sensing and detection

Multicomponent reactions (MCRs): a useful access to the synthesis of benzo-fused γ-lactams

• Edorta Martínez de Marigorta,
• Jesús M. de Los Santos,
• Ana M. Ochoa de Retana,
• Javier Vicario and
• Francisco Palacios

Beilstein J. Org. Chem. 2019, 15, 1065–1085, doi:10.3762/bjoc.15.104

• was chemoselective, furnishing in good yields the products resulting from the transfer of the less hindered arene. However, this methodology exhibits two main limitations. First, arenes 86 with electron-withdrawing groups did not react under the optimized conditions and on the other hand, the atom

• economy is quite low, since a half of the diaryliodonium salt 87 is lost in the process. Replacing the arene substrate 86 by ketones, and keeping nearly equal reaction conditions, the same authors have achieved an efficient synthesis of 3-(2-oxopropyl)- or pentacyclic isoindolinones 90 or 92 (Scheme 26

• , that rearranges to afford cationic isoindolinone moiety 95. Then, benzene derivative 86 would react by a Friedel–Crafts type reaction to form diaryl γ-lactam 88. When ketone 89 is used instead of arene 86, the enol form would act as nucleophile and upon reaction with carbocation 95, compounds 90 could

Fabrication, characterization and adsorption properties of cucurbit[7]uril-functionalized polycaprolactone electrospun nanofibrous membranes

• Changzhong Chen,
• Fengbo Liu,
• Xiongzhi Zhang,
• Zhiyong Zhao and
• Simin Liu

Beilstein J. Org. Chem. 2019, 15, 992–999, doi:10.3762/bjoc.15.97

• series of CD-functionalized electrospun nanofibers in the forms of CD-pseudopolyrotaxane [11][12], CDs/polymer [13][14][15], CD-ICs/polymer [16][17], and polymer-free CDs [5][18] or CD-ICs [19] have been fabricated. In addition, calix[8]arene (C[8])/polyacrylonitrile (PAN) composite nanofiber membranes

• [20] and supramolecular polymer nanofibers based on pillar[5]arene [21] also were prepared by the electrospinning technique. Cucurbit[n]urils (CB[n]s, n = 5–8, 10) are a family of pumpkin-shaped cyclic host molecules containing a hydrophobic cavity surrounded by two identical hydrophilic portals [22

Mechanochemistry of supramolecules

• Anima Bose and
• Prasenjit Mal

Beilstein J. Org. Chem. 2019, 15, 881–900, doi:10.3762/bjoc.15.86

• synthesis of pillar[5]arene-containing [2]rotaxanes (Figure 8). Mixing a 2:1 ratio of pillar[5]arene (wheel) with dodecanedioyl dichloride (axle) in CHCl3 resulted in the formation of pseudorotaxane 16 which was further treated with different amines (stopper) in a stainless-steel jar with 4 steel balls

• (Figure 21a). However, 1,8-dipyridylnaphthalene was used as hydrogen-bond acceptor for the [2 + 2] cycloaddition of fumaric acid derivatives (Figure 21b). In 2017 Purse and co-workers reported the host–guest chemistry of pyrogallo[4]arene (39) hexamers under mechano-milling conditions [94]. A hexameric

• of unsymmetrically substituted azobenzene [58]. a) Schematic representation for the construction of a [2]rotaxane. b) Chiu’s ball-milling approach for the synthesis of [2]rotaxanes. Mechanochemical synthesis of the smallest [2]rotaxane. Solvent-free mechanochemical synthesis of pillar[5]arene

Polyaminoazide mixtures for the synthesis of pH-responsive calixarene nanosponges

• Antonella Di Vincenzo,
• Antonio Palumbo Piccionello,
• Alberto Spinella,
• Delia Chillura Martino,
• Marco Russo and
• Paolo Lo Meo

Beilstein J. Org. Chem. 2019, 15, 633–641, doi:10.3762/bjoc.15.59

• copolymers (CyCaNSs) [16][17][18], which showed pH-dependent sequestration abilities towards different model organic substrates. The latter NSs were easily synthesized by means of a CuAAC-type reaction [19][20][21] between a heptakisazido-β-cyclodextrin and a tetrakis(propargyloxy)calix[4]arene derivative

• . More recently, we also reported the synthesis of entirely synthetic calixarene nanosponges (CaNSs) [22], which can be prepared by means of the same CuAAC approach, by reacting a tetrakis(propargyloxy)calix[4]arene with a diazidoalkane. Of course, the reaction results in the formation of bis(1,2,3

• ) of polyaminoazide mixtures, which were in turn used for the preparation of CaNSs materials with pH-tunable properties, by reaction with the (5,11,17,23-tetra(tert-butyl))-(25,26,27,28-tetrakis(propargyloxy)calix[4]arene (Ca) under the CuAAC reaction conditions. In turn, the synthon Ca is obtained by

Selective benzylic C–H monooxygenation mediated by iodine oxides

• Kelsey B. LaMartina,
• Haley K. Kuck,
• Linda S. Oglesbee,
• Asma Al-Odaini and
• Nicholas C. Boaz

Beilstein J. Org. Chem. 2019, 15, 602–609, doi:10.3762/bjoc.15.55

• intractable products, which were in many cases polyfunctionalized. Additionally, substrates containing arene rings were shown to inhibit aliphatic C–H functionalization via electrophilic trapping of reactive halogen species to form aryl chlorides and iodides. Utilizing NHPI as a less reactive hydrogen atom

• NHPI-catalyzed C–H acetoxylation reaction yielded the ester product 3a in moderate (42%) yield. This contrasts with orthoperiodic acid (H5IO6), which yielded only electrophilic arene iodination. The use of alkali metal iodate salts such as lithium, sodium, and potassium iodate as the terminal oxidant

• decatungstate [58]. Substrates containing tertiary C–H bonds, such as 1-isopropyl-4-methylbenzene (6b), were essentially unreactive under the developed conditions, returning starting alkyl arene with only a trace of acetoxylated product 7b (see Supporting Information File 1, Figure S11) [59]. Previous work on

Dirhodium(II)-catalyzed [3 + 2] cycloaddition of N-arylaminocyclopropane with alkyne derivatives

• Wentong Liu,
• Yi Kuang,
• Zhifan Wang,
• Jin Zhu and
• Yuanhua Wang

Beilstein J. Org. Chem. 2019, 15, 542–550, doi:10.3762/bjoc.15.48

• 3,5-dimethyl compound 1d afforded the desired product 3d with an excellent yield of 91% (Table 2, entry 3). We reasoned the electron-withdrawing groups on the arene increased the nitrogen–hydrogen bond dissociation energy (BDEN–H) of compound 1 [21], decreasing the rate of ring opening. Substrates 1i

N-Arylphenothiazines as strong donors for photoredox catalysis – pushing the frontiers of nucleophilic addition of alcohols to alkenes

• Fabienne Speck,
• David Rombach and
• Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2019, 15, 52–59, doi:10.3762/bjoc.15.5

• characteristics of the derivatives 1–9 were analyzed and compared (Figure 3). The parent compound N-phenylphenothiazine (1) shows an absorption maximum at 320 nm. Substitution of the arene moiety results in a shift of the absorption maxima due to a change in the HOMO–LUMO gaps. It turned out that the introduction

• found to occur at E(1+·/1) = 0.75 V (vs SCE). The substitution of the arene moiety by one (see 7) or two fluorine substituents (see 8) only leads to a shift in the reduction potential of about 0.06 V. This trend was expected due to the lower electron density of these two N-phenylphenothiazines at the

• arene moiety. However, the effect by the pure σ-acceptor fluorine is not very pronounced. In the case of the 4-NO2 substituted derivative 6 the pronounced influence of the π-acceptor shifts the reduction potential to a value of up to E(6+·/6) = 0.89 V (vs SCE). Substitution of the N-aryl moiety by

Ruthenium-based olefin metathesis catalysts with monodentate unsymmetrical NHC ligands

• Veronica Paradiso,
• Chiara Costabile and
• Fabia Grisi

Beilstein J. Org. Chem. 2018, 14, 3122–3149, doi:10.3762/bjoc.14.292

• converted completely within a few hours into complex 2 due to the formation of an intramolecular carbene–arene bond between the benzylidene carbon atom and the ortho position of the N-phenyl ligand (Figure 3). According to the authors, the mechanism of the reaction that occurs only in the presence of oxygen

• containing a monosubstituted backbone and two different N-aryl groups (202–204, Figure 37) [63]. The idea behind this new category of compounds lied in the possibility of an efficient transfer of chirality from the backbone group to the metal center through a significant twisting of the monosubstituted arene

Synthesis of aryl sulfides via radical–radical cross coupling of electron-rich arenes using visible light photoredox catalysis

• Amrita Das,
• Mitasree Maity,
• Simon Malcherek,
• Burkhard König and
• Julia Rehbein

Beilstein J. Org. Chem. 2018, 14, 2520–2528, doi:10.3762/bjoc.14.228

• (dtbpy)]PF6 as the photocatalyst. The reaction was carried out under nitrogen under visible-light irradiation at 455 nm. The oxidation potential of this test arene is 1.02 V vs SCE, which allows oxidation by [Ir(dF(CF3)ppy)2(dtbpy)]PF6 having an estimated excited state oxidation potential of 1.21 V vs

• -methoxyphenyl) disulfide was employed as the thiolating agent (3h). With symmetrical arenes, diarylation was observed. The initially formed mono-arylated product is more reactive than the starting material and reacts to the diarylthiol product. When 1-phenyl-1H-pyrrole-2,5-dione was employed as the arene, the

• sulfenylation occurred exclusively at the double bond instead at the arene to give the product 3k in 58% yield and a trace amount of diarylation product of the aromatic ring. When the more difficult to oxidize 2-methoxynaphthalene was used as substrate, the product 3l was obtained in only 30% yield indicating

Calixazulenes: azulene-based calixarene analogues – an overview and recent supramolecular complexation studies

• Paris E. Georghiou,
• Shofiur Rahman,
• Abdullah Alodhayb,
• Hidetaka Nishimura,
• Jaehyun Lee,
• Atsushi Wakamiya and
• Lawrence T. Scott

Beilstein J. Org. Chem. 2018, 14, 2488–2494, doi:10.3762/bjoc.14.225

• -containing structures have gained much recent attention. Among the least-studied to date, however, have been the azulene unit-containing calix[4]arene analogues. In 1988 Asao et al. reported the synthesis of the first azulene analogue of the calixarenes, which they called “azulenophane” 2 [14]. They used a

Hydroarylations by cobalt-catalyzed C–H activation

• Rajagopal Santhoshkumar and
• Chien-Hong Cheng

Beilstein J. Org. Chem. 2018, 14, 2266–2288, doi:10.3762/bjoc.14.202

• , Whiteoak’s group reported a cobalt-catalyzed hydroarylation of terminal alkenes with amides 39 [78]. The reaction of vinyl ketones with amides provided alkylated product 40, whereas acrolein resulted in biologically useful azepinones in good yields (Scheme 26b). N-Pyrimidylindole is a highly reactive arene

• , a plausible mechanism was proposed. The reaction starts with the generation of the active cobalt(III) species G1 from [Cp*CoI2(CO)], AgSbF6, and arene 53. Subsequently, C–H metallation of G1 by ligand-to-ligand hydrogen transfer provides cobaltacycle G2 and an allene insertion gives intermediate G3

• form bicyclic cobaltacycle H1. After the reversible coordination of arene 55 with H1 to generate intermediate H2, ortho C–H cobaltation provides complex H3, which changed into product 56 and Co(I) catalyst by reductive elimination of H3. 5. Hydroarylation of C=X (X = N, O) bonds 5.1 Low-valent cobalt

Coordination-driven self-assembly of discrete Ru₆–Pt₆ prismatic cages

• Aderonke Ajibola Adeyemo and
• Partha Sarathi Mukherjee

Beilstein J. Org. Chem. 2018, 14, 2242–2249, doi:10.3762/bjoc.14.199

• Aderonke Ajibola Adeyemo Partha Sarathi Mukherjee Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560 012, India 10.3762/bjoc.14.199 Abstract The coordination-driven self-assembly of two new Ru6–Pt6 hexanuclear trigonal prismatic cages comprising arene

• supramolecular chemistry leading to the formation of a single major product. Keywords: arene–ruthenium(II); heterometallic cages; platinum metalloligand; self-assembly; supramolecular architectures; Introduction Coordination-driven self-assembly of discrete architectures has evolved as a unique protocol to

• structural rigidity while the second metal is the electron-acceptor building block. The facile self-assembly of 2D-heterobimetallic supramolecular architectures are well reported in the literature [24][93][94], however, 3D-heterobimetallic systems are still less explored [95][96][97]. Dinuclear arene

Synthesis of a water-soluble 2,2′-biphen[4]arene and its efficient complexation and sensitive fluorescence enhancement towards palmatine and berberine

• Xiayang Huang,
• Xinghua Zhang,
• Tianxin Qian,
• Junwei Ma,
• Lei Cui and
• Chunju Li

Beilstein J. Org. Chem. 2018, 14, 2236–2241, doi:10.3762/bjoc.14.198

• , Shanghai 200444, P. R. China 10.3762/bjoc.14.198 Abstract A water-soluble 2,2′-biphen[4]arene (2,2’-CBP4) containing eight carboxylato moieties was synthesized and characterized. Its complexation behavior towards two alkaloids, palmatine (P) and berberine (B), was investigated by means of fluorescence and

• specific structures and interesting host–guest properties [21][22][23][24][25][26][27][28][29][30][31][32]. Water-soluble pillar[n]arene derivatives, especially those containing carboxylato moieties, showed low cell toxicity and good biocompatibility, and have been applied in biomedical applications such

• as bioimaging and self-assembled drug delivery systems [33][34][35][36][37][38][39][40]. For example, our group demonstrated a direct host–guest complexation-based drug delivery system for oxaliplatin by carboxylatopillar[6]arene [36]. The encapsulation could not only improve the drug‘s stability in

Evaluation of dispersion type metal···π arene interaction in arylbismuth compounds – an experimental and theoretical study

• Ana-Maria Preda,
• Małgorzata Krasowska,
• Lydia Wrobel,
• Philipp Kitschke,
• Phil C. Andrews,
• Jonathan G. MacLellan,
• Lutz Mertens,
• Marcus Korb,
• Tobias Rüffer,
• Heinrich Lang,
• Alexander A. Auer and
• Michael Mehring

Beilstein J. Org. Chem. 2018, 14, 2125–2145, doi:10.3762/bjoc.14.187

• , Professur Anorganische Chemie, 09107 Chemnitz, Germany 10.3762/bjoc.14.187 Abstract The dispersion type Bi···π arene interaction is one of the important structural features in the assembly process of arylbismuth compounds. Several triarylbismuth compounds and polymorphs are discussed and compared based on

• the analysis of single crystal X-ray diffraction data and computational studies. First, the crystal structures of polymorphs of Ph3Bi (1) are described emphasizing on the description of London dispersion type bismuth···π arene interactions and other van der Waals interactions in the solid state and

• the effect of it on polymorphism. For comparison we have chosen the substituted arylbismuth compounds (C6H4-CH═CH2-4)3Bi (2), (C6H4-OMe-4)3Bi (3), (C6H3-t-Bu2-3,5)3Bi (4) and (C6H3-t-Bu2-3,5)2BiCl (5). The structural analyses revealed that only two of them show London dispersion type bismuth···π arene

Calix[6]arene-based atropoisomeric pseudo[2]rotaxanes

• Carmine Gaeta,
• Carmen Talotta and
• Placido Neri

Beilstein J. Org. Chem. 2018, 14, 2112–2124, doi:10.3762/bjoc.14.186

• different conformations adopted by the wheel are reported here. Upon threading hexahexyloxycalix[6]arene 1 with ammonium axles 2+ or 3+, bearing biphenyl or trifluoromethylbenzyl moieties, respectively, two atropoisomeric pseudorotaxanes were formed in which the calix[6]-wheel 1 adopts the 1,2,3-alternate

• -flat wheels, such as calixarenes or cyclodextrins, are threaded along an axle to give a pseudo[3]rotaxane architecture V–VII (Figure 2), where three sequential stereoisomers can arise. We showed that this stereoisomerism can be effectively controlled when two calix[6]arene wheels are threaded along a

• chemical shift of the ArCH2Ar methylene C, which is 30–33 ppm for the syn-orientation of the proximal phenol rings and typically 36–39 ppm with anti-positioned phenol rings as in alternate conformations. As exemplified above, the calix[6]arene macrocycle has been widely used as wheel for the assembly of

Revisiting ring-degenerate rearrangements of 1-substituted-4-imino-1,2,3-triazoles

• James T. Fletcher,
• Matthew D. Hanson,
• Joseph A. Christensen and
• Eric M. Villa

Beilstein J. Org. Chem. 2018, 14, 2098–2105, doi:10.3762/bjoc.14.184

• -phenyl substituent and the triazole ring is 28°, the dihedral angle between the imino group and triazole ring is 0.5° and the dihedral angle between the phenyl and imino group is 32°. This structural detail supports the ability of the 1-triazolyl and imino arene units to communicate electronically