Enantioselective Diels–Alder reaction of anthracene by chiral tritylium catalysis

• Qichao Zhang,
• Jian Lv and
• Sanzhong Luo

Beilstein J. Org. Chem. 2019, 15, 1304–1312, doi:10.3762/bjoc.15.129

• , the enantioselectivity was low in most cases. In addition, the synthetic efforts to access these chiral cations were generally non-trivial which limited their further development. Recently, we developed a chiral ion-pair strategy for asymmetric carbocation catalysis, with chiral trityl phosphate as

• found that less than 6% of trityl phosphate (TP) dissociated to trityl cations in the presence of a polar substrate such trifluoropyruvate [20]. In order to improve the efficiency of the dissociation, we started by first studying the properties of tritylium salts with a weakly coordinating metal-based

• Lewis acid. An estimation based on UV absorption showed that approximately 76% of TP dissociated into trityl cations in the presence of InBr3. On the other hand, tritylium salts with a weakly coordinating metal-based monophosphate or bisphosphate anion could also be obtained when trityl bromide was

Self-assembly behaviors of perylene- and naphthalene-crown macrocycle conjugates in aqueous medium

• Xin Shen,
• Bo Li,
• Tiezheng Pan,
• Jianfeng Wu,
• Yangxin Wang,
• Jie Shang,
• Yan Ge,
• Lin Jin and
• Zhenhui Qi

Beilstein J. Org. Chem. 2019, 15, 1203–1209, doi:10.3762/bjoc.15.117

• water-soluble crown macrocycle 3 was synthesized according to reported protocols, by using potassium cations as template [86][87]. The primary amine group in 3 offers diverse reaction pathways to design crown ethers appended LMW gelators, dendrimers and polymers [88][89][90][91][92]. In order to

Precious metal-free molecular machines for solar thermal energy storage

• Meglena I. Kandinska,
• Snejana M. Kitova,
• Vladimira S. Videva,
• Stanimir S. Stoyanov,
• Stanislava B. Yordanova,
• Stanislav B. Baluschev,
• Silvia E. Angelova and
• Aleksey A. Vasilev

Beilstein J. Org. Chem. 2019, 15, 1096–1106, doi:10.3762/bjoc.15.106

• identified to form complexes with alkaline-earth metal cations with higher stability constant than the respective trans isomer forms [14][15][18]. Lednev et al. proposed as an explanation of the difference in the determined stability constants values for the complexes with cis/trans isomers the formation of

• defined their photophysical behavior in neat acetonitrile (ACN) solution and in the presence of barium cations. Figure 1 shows the absorption spectra of dyes 4a–d measured at different concentrations (cM) of Ba(ClO4)2. All dye solutions have similar absorption profiles with a broad long wavelength band in

• high Ba2+ concentrations. The explanation is related to the size of the barium cation which does not intercalate completely in the crown ether cavity. This assumption is confirmed by the slight downfield shift of the signals in the 1H NMR spectrum of dye 4b in the presence of Ba2+ cations compared to

Mechanistic investigations on multiproduct β-himachalene synthase from Cryptosporangium arvum

• Jan Rinkel and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2019, 15, 1008–1019, doi:10.3762/bjoc.15.99

• , Supporting Information File 1). To shed light on the stereochemical course of the 1,3-hydride shift connecting cations D and F, a series of labelling experiments were conducted to determine the origin of the shifting hydrogen (C-1) and its destination (C-10) for 1 (Figure 8). A comparison of the 13C NMR

Mechanochemistry of supramolecules

• Anima Bose and
• Prasenjit Mal

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

• [7] followed by the lock-and-key concept of Emil Fischer in 1894 [8]. Weak or non-covalent interactions had been used systematically in the early 1960s by Lehn, Cram and Pederson to create targeted supramolecular architectures [9]. Small molecules, anions or cations could be assembled spontaneously

Coordination chemistry and photoswitching of dinuclear macrocyclic cadmium-, nickel-, and zinc complexes containing azobenzene carboxylato co-ligands

• Jennifer Klose,
• Tobias Severin,
• Peter Hahn,
• Alexander Jeremies,
• Jens Bergmann,
• Daniel Fuhrmann,
• Jan Griebel,
• Bernd Abel and
• Berthold Kersting

Beilstein J. Org. Chem. 2019, 15, 840–851, doi:10.3762/bjoc.15.81

• (7·ClO4·xEtOH; x ≈ 4): Crystals of [Ni2L(μ-azo-NMe2)]ClO4.xEtOH obtained from a mixed ethanol/acetonitrile solvent system are triclinic, space group P. The asymmetric unit comprises two crystallographically independent [Ni2L(μ-azo-NMe2)]+ cations, two ClO4– ions and 8 EtOH solvate molecules. The

• )]+ cations are structurally very similar as illustrated in Figure 8. In cation A, the co-ligand is nearly flat and coplanar with the Ni2 carboxylato plane. In cation B, the benzene rings are tilted about the azo group and the Ni2carboxlyato plane by angles of ≈32.3° and 37.5°, respectively. Interestingly, no

• blue, O red, S yellow, metals flesh (Zn, Cd) or green (Ni)). Space filling representation of the packing of two symmetry-related [Zn2L(μ-azo-NMe2)]+ cations in crystals of 5·1.5MeCN. The ClO4− anions and solvate molecules are omitted for clarity. Structure of the [Cd2L(μ-azo-NMe2)]+ cation in crystals

Design, synthesis and spectroscopic properties of crown ether-capped dibenzotetraaza[14]annulenes

• Krzysztof M. Zwoliński and
• Julita Eilmes

Beilstein J. Org. Chem. 2019, 15, 617–622, doi:10.3762/bjoc.15.57

• crown ethylene bridges fall within the range of 5.4–5.5 Hz, expected for gauche stereochemistry. Such a relaxed crown conformation is suitable for accommodation of large alkali and alkaline-earth cations. The general features of FTIR-ATR spectra of receptors 3a and 3b are substantially similar to each

Syntheses and chemical properties of β-nicotinamide riboside and its analogues and derivatives

• Mikhail V. Makarov and
• Marie E. Migaud

Beilstein J. Org. Chem. 2019, 15, 401–430, doi:10.3762/bjoc.15.36

• hexachloroacetone [28][71] or cobalt(II) acetate in the presence of hydrogen peroxide followed by removal of the cobalt cations with QuadraSil AP resin [60]. The nature of the counter anion vary as a function of the conditions applied. Reduction of N1-substituted 3-nicotinamide salts to the corresponding 1,4

Study on the regioselectivity of the N-ethylation reaction of N-benzyl-4-oxo-1,4-dihydroquinoline-3-carboxamide

• Pedro N. Batalha,
• Luana da S. M. Forezi,
• Maria Clara R. Freitas,
• Nathalia M. de C. Tolentino,
• Ednilsom Orestes,
• José Walkimar de M. Carneiro,
• Fernanda da C. S. Boechat and
• Maria Cecília B. V. de Souza

Beilstein J. Org. Chem. 2019, 15, 388–400, doi:10.3762/bjoc.15.35

• carboxamide group, may contribute to enhance the bioactivity. This fact could be explained by the coplanarity induced by the C-4 carbonyl hydrogen bond interactions with biological targets [3] or complexation with physiological metal cations such as magnesium and zinc [23]. Besides the derivatives 3a and 3b

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

• fast access to a wide variety of catalysts. Recently it was shown that the radical cation of the photoredox catalyst can play a key role in photoinduced oxidation chemistry [16]. This is rather unusual due to the usually short lifetime of radical cations in solution attributed to their low-lying

Organometallic vs organic photoredox catalysts for photocuring reactions in the visible region

• Aude-Héloise Bonardi,
• Frédéric Dumur,
• Guillaume Noirbent,
• Jacques Lalevée and
• Didier Gigmes

Beilstein J. Org. Chem. 2018, 14, 3025–3046, doi:10.3762/bjoc.14.282

• catalytic cycles used in organic chemistry, the development of photoredox catalysis for photopolymerization reactions has been proposed. It has emerged as a significant innovation in the field of photoinitiated polymerization. Photoredox catalysis is a new strategy to generate radicals and/or cations upon

• named reduction agent, RA2 in Figure 1) by a redox reaction. In a reductive cycle, the PC* reacts first with a reduction agent (in Figure 1, RA1) which leads to PC●− and RA1●+. Then, PC can be regenerated with an oxidation agent (OA2). Radicals and cations are generated in these cycles [16]. As we can

• the case of a d5 high spin octahedral complex in Figure 4. As for LMCT, MLCT give intense band in UV spectrum. 1.4 Mechanisms in polymerization reactions Free radical polymerization or/and cationic polymerization can be initiated by photoredox catalysis. Respectively, radicals or/and cations must be

Nucleofugal behavior of a β-shielded α-cyanovinyl carbanion

• Rudolf Knorr and
• Barbara Schmidt

Beilstein J. Org. Chem. 2018, 14, 3018–3024, doi:10.3762/bjoc.14.281

• . Alternatively, carbonyl additions to 2Li might be generally retarded (relative to protonations) on account of the clustered [4] ground state structure of 2Li in solution. Electrophilic cations (Li+ or K+) are not necessary (albeit perhaps helpful) for the addition of the carbanion unit of 2Li or 2K to carbonyl

1,8-Bis(dimethylamino)naphthyl-2-ketimines: Inside vs outside protonation

• A. S. Antonov,
• A. F. Pozharskii,
• P. M. Tolstoy,
• A. Filarowski and
• O. V. Khoroshilova

Beilstein J. Org. Chem. 2018, 14, 2940–2948, doi:10.3762/bjoc.14.273

• , leading to the formation of stabilised cations. In our recent work, we observed for the first time that the ortho-ketimino group in 4a can compete with the proton sponge moiety for the proton, which results in the formation of equilibria between the forms 4b (protonated to the proton sponge fragment) and

• Synthesis of DMAN-ortho-ketimines and their cations Target compounds 4a–7a were synthesised by techniques previously developed in our laboratory (Scheme 4) [7][8]. Compounds 4a–6a were obtained by the treatment of the ortho-lithium derivative 8 with the corresponding nitrile (path a). Unfortunately, the

Generation of 1,2-oxathiolium ions from (arysulfonyl)- and (arylsulfinyl)allenes in Brønsted acids. NMR and DFT study of these cations and their reactions

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

Beilstein J. Org. Chem. 2018, 14, 2897–2906, doi:10.3762/bjoc.14.268

• , D2SO4), (arysulfonyl)allenes (ArSO2–CR1=C=CR2R3) and (arylsulfinyl)allenes (ArSO–CR1=C=CR2R3) undergo cyclization into the corresponding stable 1,2-oxathiolium ions, which were studied by means of NMR and DFT calculations. Quenching of solutions of these cations with low nucleophilic media, aqueous HCl

• of species A, B. The comparison of 13C NMR spectra of oxathiolylium A, B and oxaphospholium P1, P2 ions shows that for the former species the signal of carbon C5 is about 10–15 ppm downfield shifted relatively the same signal in the cations P1, P2 (Table 1). This reveals that carbon C5 bears a rather

• large positive charge in cations A, B. For dication Bh, different signals were detected for quaternary carbons C5 and C5', and vinyl carbons C4 and C4', etc., that, probably, indicates formation of two diastereomers (one meso-form and one pair of enantiomers) due to the stereogenic sulfur centers. In

Oxidative and reductive cyclization in stiff dithienylethenes

• Michael Kleinwächter,
• Ellen Teichmann,
• Lutz Grubert,
• Martin Herder and
• Stefan Hecht

Beilstein J. Org. Chem. 2018, 14, 2812–2821, doi:10.3762/bjoc.14.259

• radical cations [34][35] and simple dithienylethenes [36][37][38]. As such, we postulate an equilibrium between both E- and Z-radical cations with the latter rapidly reacting to the closed isomer. To gain a deeper mechanistic understanding of the oxidative cyclization, the evolution of the UV–vis

An overview on recent advances in the synthesis of sulfonated organic materials, sulfonated silica materials, and sulfonated carbon materials and their catalytic applications in chemical processes

• Hashem Sharghi,
• Pezhman Shiri and
• Mahdi Aberi

Beilstein J. Org. Chem. 2018, 14, 2745–2770, doi:10.3762/bjoc.14.253

• cations. The 1H NMR spectrum displayed all protons of two -NMe2 groups as a singlet in the region of 3–3.2 ppm. On the other hand, the carbon chemical shift of C=N appeared around 134.7 ppm and 119.9 ppm attributed to two types of the chemical environment of the C=N carbon [46]. The three-component

Targeting the Pseudomonas quinolone signal quorum sensing system for the discovery of novel anti-infective pathoblockers

• Christian Schütz and
• Martin Empting

Beilstein J. Org. Chem. 2018, 14, 2627–2645, doi:10.3762/bjoc.14.241

• deprivation, pH, anaerobiosis, as well as biocides, polyamines, cations and carbon sources could also act as external triggers leading to adaptive resistance. The common effect of these stimuli seems to be an alteration in expression patterns ultimately impacting, e.g., efflux pump or enzymatic activity, as

Carbonylonium ions: the onium ions of the carbonyl group

• Daniel Blanco-Ania and
• Floris P. J. T. Rutjes

Beilstein J. Org. Chem. 2018, 14, 2568–2571, doi:10.3762/bjoc.14.233

• Daniel Blanco-Ania Floris P. J. T. Rutjes Institute for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ Nijmegen, The Netherlands 10.3762/bjoc.14.233 Abstract The nomenclature of cations R1C(=O+R3)R2 (R1, R2, R3 = H or organyl) has been examined and shown to be in a state

Catalyst-free synthesis of 4-acyl-NH-1,2,3-triazoles by water-mediated cycloaddition reactions of enaminones and tosyl azide

• Lu Yang,
• Yuwei Wu,
• Yiming Yang,
• Chengping Wen and
• Jie-Ping Wan

Beilstein J. Org. Chem. 2018, 14, 2348–2353, doi:10.3762/bjoc.14.210

• cycloaddition of azides with activated dipolarophiles such as strained cyclic alkynes, enamines, enolates, electron-deficient olefins, ylides, iminium cations and alkyne anions, etc., have been identified as reliable approaches to access 1,2,3-triazole scaffolds with multiple substitution patterns [39][40][41

Dynamic light scattering studies of the effects of salts on the diffusivity of cationic and anionic cavitands

• Anthony Wishard and
• Bruce C. Gibb

Beilstein J. Org. Chem. 2018, 14, 2212–2219, doi:10.3762/bjoc.14.195

• . This is the reverse Hofmeister effect, and in complex biomacromolecules we surmise that both effects are in operation, and that in very general terms it is the balance between these that dictates the properties of a particular macromolecule under specific conditions. Cations can also induce Hofmeister

• effects, but these are usually much weaker, and we believe there are two reasons for this. First, simple metal cations are generally more strongly solvated than comparable anions that can induce Hofmeister effects. Second, the anions that predominate in biomacromolecules are carboxylates, phosphates and

• titration with various halide salts. The fifteen salts studied were a matrix of the alkali metal cations Li+, Na+, K+, and Cs+ in combination with the halides F− through I−, the one omission being poorly soluble lithium fluoride (maximum solubility = 0.134 g mL−1). Unsurprisingly, given the pKa values of

Tetrathiafulvalene – a redox-switchable building block to control motion in mechanically interlocked molecules

• Hendrik V. Schröder and
• Christoph A. Schalley

Beilstein J. Org. Chem. 2018, 14, 2163–2185, doi:10.3762/bjoc.14.190

• connected by a C=C double bond. The first oxidation converts one ring into an aromatic 6π-electron system, which is further stabilized by a mixed-valence resonance structure. The second oxidation yields two aromatic 1,3-dithiolium cations (2 × 6π electrons) which are connected by a C–C single bond. The

• complexes in solution can be easily traced by the emergence and fading of these characteristic charge-transfer bands. Another outstanding feature of TTFs is that their radical cations can reversibly form cofacial dimers (Figure 3) [34][35][36]. The two monomers 1 and 1●+ spontaneously self-assemble into a

• dimer interaction can be an emergent low-energy absorption band, usually in the NIR region. Both monomers show usually no absorption in this region. The radical-cation dimer (1●+)2 instead forms from two 1●+ radical cations and exhibits a very unusual binding situation. Whereas both monomers are

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

• cations, and have impacted fields that include bioimaging [26][27] and chemosensing [28][29]. Surprisingly, the reported examples partnering 1,2,3-triazole and imine N-donor groups are limited [30][31][32], despite the ubiquity of such Schiff base subunits in coordination chemistry. 4-Iminotriazole

Synthesis and supramolecular self-assembly of glutamic acid-based squaramides

• Juan V. Alegre-Requena,
• Marleen Häring,
• Isaac G. Sonsona,
• Alex Abramov,
• Eugenia Marqués-López,
• Raquel P. Herrera and
• David Díaz Díaz

Beilstein J. Org. Chem. 2018, 14, 2065–2073, doi:10.3762/bjoc.14.180

• asymmetric catalysis and molecular recognition [5][6]. Besides, squaramides present a dual ability to recognize anions and cations through hydrogen bonding interactions, acting as ion sensors and transmembrane anion transporters [7]. This property has been crucial for the development of new drugs [8][9

Synthesis of new p-tert-butylcalix[4]arene-based polyammonium triazolyl amphiphiles and their binding with nucleoside phosphates

• Vladimir A. Burilov,
• Guzaliya A. Fatikhova,
• Mariya N. Dokuchaeva,
• Ramil I. Nugmanov,
• Diana A. Mironova,
• Pavel V. Dorovatovskii,
• Victor N. Khrustalev,
• Svetlana E. Solovieva and
• Igor S. Antipin

Beilstein J. Org. Chem. 2018, 14, 1980–1993, doi:10.3762/bjoc.14.173

• nucleotides must possess selectivity towards these anions. From this point of view, nucleotide receptors based on polyammonium cations are of great demand because the electrostatic interactions of such polyammonium systems and negatively charged phosphates are strong. Hydrogen bonding [8] and π-stacking

• MOPAC 2016 program [61] with discard of repeated duplicates. Then unique conformers were combined with calix[4]arene core, and corresponding cations and complexes with ATP/ADP were optimized by DFT calculations. For DFT calculations Priroda 16 program [62] with build-in PBE functional on L2 basis level

Rational design of boron-dipyrromethene (BODIPY) reporter dyes for cucurbit[7]uril

• Mohammad A. Alnajjar,
• Jürgen Bartelmeß,
• Robert Hein,
• Pichandi Ashokkumar,
• Mohamed Nilam,
• Werner M. Nau,
• Knut Rurack and
• Andreas Hennig

Beilstein J. Org. Chem. 2018, 14, 1961–1971, doi:10.3762/bjoc.14.171

• cyclohexylmethylammonium (cyH) cations by displacement titrations (see below) in our mixture of 30% (v/v) ACN/H2O, which gave Ka(Bnz) = 1.4 × 105 M−1 and Ka(cyH) = 1.5 × 107 M−1. This indicated that the binding affinity is lowered 100 to 1000-fold by reducing the hydrophobic effect in presence of 30% acetonitrile as also