Au(III) complexes with tetradentate-cyclam-based ligands

• Ann Christin Reiersølmoen,
• Thomas N. Solvi and
• Anne Fiksdahl

Beilstein J. Org. Chem. 2021, 17, 186–192, doi:10.3762/bjoc.17.18

• binding properties [25] and reactions with bovine serum albumin [27]. Cyclam is known as a tetraamino-macrocyclic ligand, which binds strongly to give complexes with many transition metal cations. While catalytic applications of square planar cyclam complexes are reported for metals, such as Ni [30][31

Multiswitchable photoacid–hydroxyflavylium–polyelectrolyte nano-assemblies

• Alexander Zika and
• Franziska Gröhn

Beilstein J. Org. Chem. 2021, 17, 166–185, doi:10.3762/bjoc.17.17

• , systems which respond to more than one external trigger have become of great interest [68][69][70][71][72][73]. Hydroxyflavylium cations can exhibit a network of different chemical reactions enabling these molecules to perform as a molecular level optical memory [74][75][76][77][78]. The network of

• understood with the fact that likely not every anionic charge can interact with a cationic charge due to steric reasons. No more ionically driven association occurs at even lower loading ratios for l < 0.16 as there are too many cations in the assemblies. The results for the assemblies at pH 5.0 are similar

Insight into functionalized-macrocycles-guided supramolecular photocatalysis

• Minzan Zuo,
• Krishnasamy Velmurugan,
• Kaiya Wang,
• Xueqi Tian and
• Xiao-Yu Hu

Beilstein J. Org. Chem. 2021, 17, 139–155, doi:10.3762/bjoc.17.15

• ]arene. Pillararenes have electron-rich cavities that facilitate the combination with various electron-deficient guest molecules, such as alkylammonium, pyridinium, and imidazolium cations. Compared to other macrocycles, pillararenes exhibit a high degree of symmetry and rigidity, which gives them a

Direct synthesis of anomeric tetrazolyl iminosugars from sugar-derived lactams

• Michał M. Więcław and
• Bartłomiej Furman

Beilstein J. Org. Chem. 2021, 17, 115–123, doi:10.3762/bjoc.17.12

• conformer. Therefore, once the ground conformer of the oxocarbenium ion is established, this logic may be used to predict the reaction’s stereochemistry. The same principle may be successfully applied to reactions of iminium cations. We have previously shown that in the case of glucose- and galactose

• new, chiral 2-(tetrazol-5-yl)-iminosugar based potential organocatalyst. Principle behind Woerpel’s model for prediction of the direction of nucleophile addition to oxocarbenium cations. Difference in conformational stability of glucose- and galactose-derived iminium cations and the major product of

Metal-free synthesis of biarenes via photoextrusion in di(tri)aryl phosphates

• Hisham Qrareya,
• Lorenzo Meazza,
• Stefano Protti and
• Maurizio Fagnoni

Beilstein J. Org. Chem. 2020, 16, 3008–3014, doi:10.3762/bjoc.16.250

• intermediates (triplet aryl cations [28][29] or aryl radicals [30][31]). As for the former case, the intermolecular formation of a biaryl arose from the photoheterolysis of an Ar–N bond (in arene diazonium salts or their derivatives [32][33]), of an Ar–Cl bond [34][35], of an Ar–O bond (in aryl phosphates [36

• investigations in the last decades [28][29][64][68]. Simple (electron-rich) monoaryl phosphates are known to undergo the photoheterolysis of the Ar–O bond to form aryl cations [28][36]. The presence of an electron-withdrawing group (e.g., NO2) may, however, divert the reactivity since a photoinduced solvolysis

• the presence of increasing amounts of TFE (up to 20% v/v, continuous line). Synthesis of biarenes via a) photogenerated triplet aryl cations and aryl radicals (PC = photocatalyst), b) intramolecular free radical ipso substitution, c) thermally catalyzed extrusion of CO and SO2, d) photoinduced

Chiral anion recognition using calix[4]arene-based ureido receptors in a 1,3-alternate conformation

• Tereza Horáčková,
• Jan Budka,
• Vaclav Eigner,
• Wen-Sheng Chung,
• Petra Cuřínová and
• Pavel Lhoták

Beilstein J. Org. Chem. 2020, 16, 2999–3007, doi:10.3762/bjoc.16.249

• -containing onium salts, protonated or alkylated aza-crown ethers and azacryptands, amidinium and guanidinium cations, etc. [15][16][17][18]. Due to the low directionality of the Coulomb force, the successful application of purely ionic interactions in the design of selective anion receptors is rather limited

Controlled decomposition of SF₆ by electrochemical reduction

• Sébastien Bouvet,
• Bruce Pégot,
• Stéphane Sengmany,
• Erwan Le Gall,
• Eric Léonel,
• Anne-Marie Goncalves and
• Emmanuel Magnier

Beilstein J. Org. Chem. 2020, 16, 2948–2953, doi:10.3762/bjoc.16.244

• disappearance of SF6 after 6 hours as well as all the fluorinated organic compounds. The only peak detected by 19F NMR is around −153 ppm. This value corresponds to the classical chemical shift range of a fluoride anion. Due to its broad appearance, we can postulate the association with cations coming from the

On the mass spectrometric fragmentations of the bacterial sesterterpenes sestermobaraenes A–C

• Anwei Hou and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2020, 16, 2807–2819, doi:10.3762/bjoc.16.231

• bacteria, that is characterised by an aspartate-rich motif (DDXXD) and an NSE triad (NDLXSXXXE) for binding of a trinuclear Mg2+ cluster [2][3]. The Mg2+ cations in turn bind to the diphosphate moiety of an isoprenoid diphosphate precursor and cause substrate ionisation by a diphosphate abstraction to

A heterobimetallic tetrahedron from a linear platinum(II)-bis(acetylide) metalloligand

• Matthias Hardy,
• Marianne Engeser and
• Arne Lützen

Beilstein J. Org. Chem. 2020, 16, 2701–2708, doi:10.3762/bjoc.16.220

• (acetylide)platinum(II) complex [Pt(L1)2(PBu3)2] as a linear metalloligand. The reaction of this metalloligand with iron(II) cations and pyridine-2-carbaldehyde according to the subcomponent self-assembly approach yielded decanuclear heterobimetallic tetrahedron [Fe4Pt6(L2)12](OTf)8. Thus, combination of

• complexity with homometallic assemblies becomes increasingly difficult to achieve. An approach to tackle these limitations is the use of not only one, but two different types of metal cations to form heterobimetallic aggregates [24][25][26]. Introducing two different types of metal cations within one

• chance to obtain new geometries, the combination of two different metal cations within one aggregate might also lead to enhanced or even entirely new properties and functions [40]. Searching the literature, however, it is striking that the number of heterobimetallic tetrahedra [41][42] is noticeably

Synthesis and characterization of S,N-heterotetracenes

• Astrid Vogt,
• Florian Henne,
• Christoph Wetzel,
• Elena Mena-Osteritz and
• Peter Bäuerle

Beilstein J. Org. Chem. 2020, 16, 2636–2644, doi:10.3762/bjoc.16.214

• TTA, SN4 9, and SN4'' 33 irreversible oxidation waves were obtained due to follow-up reactions of the formed radical cations and peak potentials gradually decrease from 0.81 V for TTA to 0.07 V for SN4'' 33 (Figure 2, right). As expected, the oxidation potential is substantially influenced by the

Anion exchange resins in phosphate form as versatile carriers for the reactions catalyzed by nucleoside phosphorylases

• Julia N. Artsemyeva,
• Ekaterina A. Remeeva,
• Tatiana N. Buravskaya,
• Irina D. Konstantinova,
• Roman S. Esipov,
• Anatoly I. Miroshnikov,
• Natalia M. Litvinko and
• Igor A. Mikhailopulo

Beilstein J. Org. Chem. 2020, 16, 2607–2622, doi:10.3762/bjoc.16.212

• found that phosphorolysis of uridine, thymidine, and Ara-U in the presence of Dowex® 1X8 (phosphate; Dowex-nPi) proceeded smoothly in the presence of magnesium cations in water at 20–50 °C for 54–96 h giving rise to quantitative formation of the corresponding pyrimidine bases and PF-1Pis. The resulting

Thermodynamic and electrochemical study of tailor-made crown ethers for redox-switchable (pseudo)rotaxanes

• Henrik Hupatz,
• Marius Gaedke,
• Hendrik V. Schröder,
• Julia Beerhues,
• Arto Valkonen,
• Fabian Klautzsch,
• Sebastian Müller,
• Felix Witte,
• Kari Rissanen,
• Biprajit Sarkar and
• Christoph A. Schalley

Beilstein J. Org. Chem. 2020, 16, 2576–2588, doi:10.3762/bjoc.16.209

• ferrocene [14][17]. Yet, switchable crown ethers are also widely applied as cation sensors, where the sensor activity can be controlled by external stimuli, e.g., light, the redox potential or chemical reagents [14][17]. Redox-switchable crown ethers have been shown to sense cations by the generation of an

• electrochemical output. For example, crown ethers containing tetrathiafulvalene (TTF) derivatives, which enable two reversible oxidation processes from the neutral to the dicationic state, were applied to sense various cations, e.g., alkali metal ions, Pb2+, and Ba2+ [18][19][20][21]. Furthermore, with the first

Water-soluble host–guest complexes between fullerenes and a sugar-functionalized tribenzotriquinacene assembling to microspheres

• Si-Yuan Liu,
• Xin-Rui Wang,
• Man-Ping Li,
• Wen-Rong Xu and
• Dietmar Kuck

Beilstein J. Org. Chem. 2020, 16, 2551–2561, doi:10.3762/bjoc.16.207

• sodium cations requires further studies. Despite the unusual mass spectrometric behavior of the compound, the combined spectroscopic evidence strongly supports the identity of TBTQ-(OAcG)6. After deprotection of the glucose units, the acetyl signals disappeared in the 1H and 13C NMR spectra of the target

Recent developments in enantioselective photocatalysis

• Callum Prentice,
• James Morrisson,
• Andrew D. Smith and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2020, 16, 2363–2441, doi:10.3762/bjoc.16.197

• reversible reductive quenching step to give two enantiomeric radical cations 236•+ and ent-236•+. The acidified adjacent proton can then be abstracted by a base to give the racemic radical 236•, which then undergoes HAT with a thiol HAT catalyst to complete the racemisation. If an appropriate chiral base is

• excellent yields and enantioselectivities (30 examples, up to 99:1 er). Ion pair Ion pair catalysis has interesting potential in combination with photoredox catalysis considering that the catalytic intermediates are often radical cations or anions. Despite this, there are relatively few examples of this

• dual catalytic mode. Ooi et al. reported an enantioselective synthesis of 1,2 diamines 247 from tertiary amines 248 and aldimines 249 (Scheme 39) [100]. The proposed mechanism involves a reductive quenching pathway with 248 to produce radical cations 248•+, which following deprotonation and a [1,2

Hierarchically assembled helicates as reaction platform – from stoichiometric Diels–Alder reactions to enamine catalysis

• David Van Craen,
• Jenny Begall,
• Johannes Großkurth,
• Leonard Himmel,
• Oliver Linnenberg,
• Elisabeth Isaak and
• Markus Albrecht

Beilstein J. Org. Chem. 2020, 16, 2338–2345, doi:10.3762/bjoc.16.195

• “Werner-type” triscatecholate titanium(IV) complex. Two of these monomers dimerized in a consecutive step to obtain a non-covalently linked helicate (Scheme 1). The dimerization took place via the coordination of three lithium cations acting as bridges between two monomeric complex units [13][14][15][16

• lithium cations. Chloroform showed the best induction with 32% ee followed by dichloromethane with 25% ee, both with 50% yield (Table 1). Ligand screening In a second optimization step, the chiral ligands have been varied. An increase of stereoselectivity was achieved by using the helicates with a

Design and synthesis of a bis-macrocyclic host and guests as building blocks for small molecular knots

• Elizabeth A. Margolis,
• Rebecca J. Keyes,
• Stephen D. Lockey IV and
• Edward E. Fenlon

Beilstein J. Org. Chem. 2020, 16, 2314–2321, doi:10.3762/bjoc.16.192

• on cryptands [2], and Cram on hemicarcerands [3] demonstrated that preorganized macrocycles have the ability to act as hosts for various guest cations and compounds. Their seminal work was recognized with the 1987 Nobel Prize in Chemistry. More recently, the 2016 Nobel Prize in Chemistry was won by

• Da, [M + H]+, 88; 1584.9 Da, [M + Na]+, 28; 1601.9 Da, [M + K]+, 52; 1626.8 Da, [M + Cu]+, 42. It is not surprising that the product would sequester metal cations given its electron-rich macrocyclic nature. Of course, the mass spectral data do not address whether the unknot, trefoil knot, or both

Synthetic approaches to bowl-shaped π-conjugated sumanene and its congeners

• Shakeel Alvi and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 2212–2259, doi:10.3762/bjoc.16.186

• sensory material for selective recognition of cesium cations in water. In another event, Hirao’s group has prepared trioxosumanene 40 in the presence of RuCl3 and t-BuO2H which could be used as a key building block to generate diverse significant electroactive materials by virtue of nucleophilic addition

• by virtue of ROM–RCM which on subsequent DDQ oxidation followed by HWE reaction provided the desired compound 108 (Scheme 26). In a really brilliant manner, Kasprzak and Sakurai in 2019 have created a sumanene–ferrocene dual system for selective recognition of cesium cations by means of site

• were treated with tert-butyl hydroperoxide (TBHP), two flanking benzene rings were found to be cleaved to afford 174 and 175 in impressive yields (Scheme 45) [82][83][84]. Moreover, they observed radical cations 172 and 173 formation when the same compounds were reacted with Br2 or 2,3,5,6-tetrafluoro

Photosensitized direct C–H fluorination and trifluoromethylation in organic synthesis

• Shahboz Yakubov and
• Joshua P. Barham

Beilstein J. Org. Chem. 2020, 16, 2151–2192, doi:10.3762/bjoc.16.183

• been responsible for generating more Selectfluor®-derived radical cations that drove the reaction towards difluorination to afford the product 28a. However, it is important to note that only difluorinated products were detected and no monofluorinated products were observed, regardless of whether

• [201], due to the instability of the primary radical (Figure 10). The selective fluorination of C2 over C3 may be rationalized by steric effects (rather than polarity matching), which are reported for quinuclidinium radical cations [203]. A similar selectivity for the most hydridic C(sp3)–H bond was

Naphthalene diimide–amino acid conjugates as novel fluorimetric and CD probes for differentiation between ds-DNA and ds-RNA

• Annike Weißenstein,
• Myroslav O. Vysotsky,
• Ivo Piantanida and
• Frank Würthner

Beilstein J. Org. Chem. 2020, 16, 2032–2045, doi:10.3762/bjoc.16.170

• cations and water molecules from the DNA/RNA grooves [44][45] by side arms interacting with the grooves and thereby supporting the binding. Circular dichroism experiments CD spectroscopy is an ideal method to get insight into the changes of the polynucleotide secondary structure upon binding of small

Automated high-content imaging for cellular uptake, from the Schmuck cation to the latest cyclic oligochalcogenides

• Rémi Martinent,
• Javier López-Andarias,
• Dimitri Moreau,
• Yangyang Cheng,
• Naomi Sakai and
• Stefan Matile

Beilstein J. Org. Chem. 2020, 16, 2007–2016, doi:10.3762/bjoc.16.167

• attractive approach to tackle this central challenge [1][2][3][11][12][13][14]. The noncovalent interaction between the guanidinium cations from CPPs and cell membrane-associated anions, such as phospholipids, proteoglycans, or sialic acids, is considered to enhance the cell surface accumulation of

• )pyrrole (GCP) cation 1 as a synthetic analogue of the guanidinium cations, somehow a “super-guanidinium” conceived to drive “arginine magic” [20][21] to the extreme (Figure 1) [23]. The power of the Schmuck cation to bind carboxylate and phosphate anions in competitive water has several origins [22

• ]. Firstly, in comparison to simple guanidinium cations 2 (pKa 12.5) and ammonium cations 3 (pKa 10.5), the Schmuck cation has a lower pKa value of 7 to 8 due to the increased acidity of acylguanidiniums, which favors the formation of stronger hydrogen-bonded ion pairs (Figure 1, magenta part). Secondly, the

Design, synthesis and application of carbazole macrocycles in anion sensors

• Alo Rüütel,
• Ville Yrjänä,
• Sandip A. Kadam,
• Indrek Saar,
• Mihkel Ilisson,
• Astrid Darnell,
• Kristjan Haav,
• Tõiv Haljasorg,
• Lauri Toom,
• Johan Bobacka and
• Ivo Leito

Beilstein J. Org. Chem. 2020, 16, 1901–1914, doi:10.3762/bjoc.16.157

• matrix. Permselectivity is conferred to the polymeric membrane by the addition of an ion exchanger, which is a lipophilic ion, and an ionophore. The ion exchanger provides permselectivity for anions or cations depending on whether the ion exchanger salt contains a lipophilic cation or anion, respectively

Natural dolomitic limestone-catalyzed synthesis of benzimidazoles, dihydropyrimidinones, and highly substituted pyridines under ultrasound irradiation

• Kumar Godugu,
• Venkata Divya Sri Yadala,
• Mohammad Khaja Mohinuddin Pinjari,
• Trivikram Reddy Gundala,
• Lakshmi Reddy Sanapareddy and
• Chinna Gangi Reddy Nallagondu

Beilstein J. Org. Chem. 2020, 16, 1881–1900, doi:10.3762/bjoc.16.156

• ) within 10 min (Table 5, entry 8). The reaction was expected to proceed through the activation of the carbonyl group of 2h (of which 2.0 mmol were used) by the cations (Ca2+ and Mg2+, respectively) of the NDL. This was followed by a nucleophilic attack of the NH2 groups of o-phenylenediamine (1, of which

One-pot synthesis of isosorbide from cellulose or lignocellulosic biomass: a challenge?

• Isaline Bonnin,
• Raphaël Mereau,
• Thierry Tassaing and
• Karine De Oliveira Vigier

Beilstein J. Org. Chem. 2020, 16, 1713–1721, doi:10.3762/bjoc.16.143

• are used with low concentration, a reduced salt will be formed after the neutralization step. Moreover, heteropolyacids can be precipitated via ion exchange with larger cations, e.g., K+, Cs+ and NH4+, or in certain cases even extracted to allow direct recycling. Thus, the usage of heterogeneous acid

Rearrangement of o-(pivaloylaminomethyl)benzaldehydes: an experimental and computational study

• Csilla Hargitai,
• Györgyi Koványi-Lax,
• Tamás Nagy,
• Péter Ábrányi-Balogh,
• András Dancsó,
• Gábor Tóth,
• Judit Halász,
• Angéla Pandur,
• Gyula Simig and
• Balázs Volk

Beilstein J. Org. Chem. 2020, 16, 1636–1648, doi:10.3762/bjoc.16.136

• explained by the protonation of ring tautomers 9 to 10 (Scheme 4), followed by a water elimination, and subsequent deprotonation of cations 11 to afford isoindoles 4 [3][4][5]. The protonation of the latter [6], followed by the attack of water at position 1 of cations 12, and subsequent deprotonation of

• formation of the dimer-like products 3a and 3b can be rationalized by the electrophilic attack of cations 12a,b at position 3 of isoindoles 4a,b to give cations 15a,b (Scheme 5). The reaction of the latter with water, followed by deprotonation leads to dimer-like compounds 16a,b, being the ring tautomers of

• the isolated products 3a and 3b. On the contrary, the formation of dimer-like products 8a and 8b can be explained by the electrophilic attack of cations 11c,d at position 1 (instead of position 3) of isoindoles 4c,d to afford cations 17a,b (Scheme 6), which transform to the dimer-like products 5a,b

Heterogeneous photocatalysis in flow chemical reactors

• Christopher G. Thomson,
• Ai-Lan Lee and
• Filipe Vilela

Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125

• the rate of recombination [91]. The abrupt termination of an ordered lattice continuity at a surface leads to chemical and structural differences from the bulk material. TiO2, for example, has surface hydroxides, oxygen anions, and Ti3+ cations, which produce high energy states from incomplete bonding