Switchable molecular tweezers: design and applications

• Pablo Msellem,
• Maksym Dekthiarenko,
• Nihal Hadj Seyd and
• Guillaume Vives

Beilstein J. Org. Chem. 2024, 20, 504–539, doi:10.3762/bjoc.20.45

• first part will be devoted to chemically responsive tweezers, including stimuli such as pH, metal coordination, and anion binding. Then, redox-active and photochemical tweezers will be presented. Keywords: coordination; molecular recognition; molecular switches; photoswitch; redox; supramolecular

• guests with an anion-binding stimulus. This system could further be tuned and adapted by increasing the macrocycle size or by modifying the TTF groups. Indeed, the authors later reported the allosterically regulated complexation of Li+ encapsulated C60 (Li+@C60) in TTF-calix[4]pyrroles and benzoTTF-calix

• a porphyrin carboxylate anion as the effector. This allowed the generation of photoinduced charge-separated states with extended lifetimes in a supramolecular triad [74]. Another switching unit controlled by an anion-binding stimulus is bis-indole, reported by Jang and co-workers (Figure 19a) [75

CuAAC-inspired synthesis of 1,2,3-triazole-bridged porphyrin conjugates: an overview

• Dileep Kumar Singh

Beilstein J. Org. Chem. 2023, 19, 349–379, doi:10.3762/bjoc.19.29

• % yield using Cu(MeCN)4PF6 and triethylamine in anhydrous DMF. This ‘capped’ porphyrin was designed so that the rigid triazole linkers prevent the capping group from collapsing onto the porphyrin. Gilday et al. [60] also synthesized porphyrin 142 and studied its anion-binding properties and found that it

• has very strong anion-binding affinities for various anions. In 2019, Ol’shevskaya [61] and co-workers synthesized meso-tetratriazole-bridged fluorinated porphyrin-maleimine conjugates 145a–c in 54–58% yields by using the CuAAC reaction between azidoporphyrins 143a,b and N-propargylmaleimide (144) in

• excellent yields using Zn(OAc)2 in a CHCl3/MeOH mixture. Their UV–vis titration study revealed that these host systems exhibit strong anion-binding affinities. Furthermore, with the help of kinetic studies, the absorption efficiency of malachite green dye was investigated by using free-base porphyrins 171a

Catalytic aza-Nazarov cyclization reactions to access α-methylene-γ-lactam heterocycles

• Bilge Banu Yagci,
• Selin Ezgi Donmez,
• Onur Şahin and
• Yunus Emre Türkmen

Beilstein J. Org. Chem. 2023, 19, 66–77, doi:10.3762/bjoc.19.6

• -unsaturated acyl chlorides to afford substituted α-methylene-γ-lactam heterocycles. The reactions proceed effectively in the presence of catalytic (20 mol %) amounts of AgOTf as an anion exchange agent or hydrogen-bond donors such as squaramides and thioureas as anion-binding organocatalysts. The aza-Nazarov

• isolated in 54% yield (Table 1, entry 8). The exchange of chloride with the non-coordinating BF4− anion, driven by the precipitation of NaCl, is proposed to be responsible for this positive result. Next, we turned our attention to the use of hydrogen-bond donors as anion-binding catalysts [57][58]. To this

• amount to promote the aza-Nazarov reactions investigated in this study, the results discussed above showcase the potential of strong hydrogen-bond donors as effective anion binding catalysts for this transformation. Finally, it should be noted that all aza-Nazarov products that are presented in Table 1

Bioinspired tetraamino-bisthiourea chiral macrocycles in catalyzing decarboxylative Mannich reactions

• Hao Guo,
• Yu-Fei Ao,
• De-Xian Wang and
• Qi-Qiang Wang

Beilstein J. Org. Chem. 2022, 18, 486–496, doi:10.3762/bjoc.18.51

• anion binding property and potent electrophilic activation ability [31][32][33][34][35][36]. To incorporate extra functionality, tertiary amine groups can be also embedded as Lewis base sites for realizing electrophilic/nucleophilic cooperative catalysis [37][38][39]. For this purpose, one kind of

New advances in asymmetric organocatalysis

• Radovan Šebesta

Beilstein J. Org. Chem. 2022, 18, 240–242, doi:10.3762/bjoc.18.28

• by a review article devoted to aza-Michael reactions of amines and amides [17]. The evolution of the understanding of noncovalent activation modes led to the realization that anion-binding is a critical feature in many transformations. Halide anions are highly relevant and widely occurring within

Asymmetric organocatalytic Michael addition of cyclopentane-1,2-dione to alkylidene oxindole

• Estelle Silm,
• Ivar Järving and
• Tõnis Kanger

Beilstein J. Org. Chem. 2022, 18, 167–173, doi:10.3762/bjoc.18.18

• bifunctional hydrogen-bonding catalyst would activate both CPD via a tertiary amino group of a quinuclidine moiety acting as a base via anion-binding, and an oxindole through the squaramide or thiourea moieties of the catalyst as hydrogen bond donors (Figure 1) [29][30][31][32]. Therefore, squaramide and

Halides as versatile anions in asymmetric anion-binding organocatalysis

• Lukas Schifferer,
• Martin Stinglhamer,
• Kirandeep Kaur and
• Olga García Macheño

Beilstein J. Org. Chem. 2021, 17, 2270–2286, doi:10.3762/bjoc.17.145

• development of the research area of asymmetric anion-binding organocatalysis. Key early elucidation studies with chloride as counter-anion confirmed this type of alternative activation, which was then exploited in several processes and contributed to the advance and consolidation of anion-binding catalysis as

• the cationic reactive species. Keywords: anion binding; asymmetric catalysis; halide anions; hydrogen donors; noncovalent interactions; Introduction Halogens and the respective anionic halides occupy an essential role in natural and chemical processes [1][2][3][4]. While in chemical syntheses

• challenging to design small molecule catalysts that resemble anion-binding properties of enzymes. Hence, a major challenge of small organic receptors to mimic nature’s capability of binding to the targeted anions resides in the supramolecular properties of enzymes and co-factors to form exact matching binding

Asymmetric organocatalyzed synthesis of coumarin derivatives

• Natália M. Moreira,
• Lorena S. R. Martelli and
• Arlene G. Corrêa

Beilstein J. Org. Chem. 2021, 17, 1952–1980, doi:10.3762/bjoc.17.128

• the desired transformation by using only one catalyst [70]. In this sense, an efficient asymmetric organocatalytic reaction was reported by Zhang et al. for the synthesis of 2,8-dioxabicyclo[3.3.1]nonanes [71]. A combination of catalysts 7 and 110, involving iminium and anion-binding catalysis

Selected peptide-based fluorescent probes for biological applications

• Debabrata Maity

Beilstein J. Org. Chem. 2020, 16, 2971–2982, doi:10.3762/bjoc.16.247

• peptidic arms equipped with lysine and an artificial strong anion binding site, the guanidinocarbonylpyrrole (GCP) moiety (Figure 2A). These arms also contain tryptophan for dissimilar aromatic interactions with different nucleobases. The fluorescence intensity of probe 1 increases by more than 4-fold at

• -Phe/Trp–Lys–Gly peptidic arms and an artificial anion binding GCP moiety at both termini for 14-3-3 proteins recognition. They have attached an environment sensitive aminonaphthimide fluorophore on a third arm as fluorescence-based reporter. Compounds 7 and 8 show a weak fluorescence band around 545

• peptide shows “switch-on” fluorescence response upon interaction with nucleic acids. Reproduced with permission from [32], Maity et al., “Peptide‐Based Probes with an Artificial Anion‐Binding Motif for Direct Fluorescence “Switch‐On” Detection of Nucleic Acid in Cells”, Chem. – Eur. J. © 2017 Wiley‐VCH

UV resonance Raman spectroscopy of the supramolecular ligand guanidiniocarbonyl indole (GCI) with 244 nm laser excitation

• Tim Holtum,
• Vikas Kumar,
• Daniel Sebena,
• Jens Voskuhl and
• Sebastian Schlücker

Beilstein J. Org. Chem. 2020, 16, 2911–2919, doi:10.3762/bjoc.16.240

• strong dimerization based on zwitterion formation at neutral pH, as described for GCP (Kdim >102 in water) [29] as well as for a GCI derivative [30], which would interfere with the anion binding. Solid benzoic acid and RGD were purchased from Fluka Analytical and Sigma-Aldrich, respectively. Both

Optical detection of di- and triphosphate anions with mixed monolayer-protected gold nanoparticles containing zinc(II)–dipicolylamine complexes

• Lena Reinke,
• Julia Bartl,
• Marcus Koch and
• Stefan Kubik

Beilstein J. Org. Chem. 2020, 16, 2687–2700, doi:10.3762/bjoc.16.219

• immobilized zinc(II)–dipicolylamine groups increased. A nanoparticle containing a 9:1 ratio of the solubilizing and the anion-binding ligand showed a color change at diphosphate and triphosphate concentrations as low as 10 μmol/L, for example, and precipitated at slightly higher concentrations

• that the anion binding must involve more than one receptor unit to induce nanoparticle crosslinking (Figure 1). The use of mixed monolayer-protected AuNPs moreover allows varying the ratio of the ligands on the nanoparticle surface, of which one is responsible for the analyte recognition, while the

• the nonaggregated to the aggregated state. This behavior is typical for multivalent systems in which individual receptor units act in a cooperative fashion, indicating that the simultaneous participation of the surface-bound receptor units in anion binding had a crucial effect on the AuNP behavior

Azo-dimethylaminopyridine-functionalized Ni(II)-porphyrin as a photoswitchable nucleophilic catalyst

• Jannis Ludwig,
• Julian Helberg,
• Hendrik Zipse and
• Rainer Herges

Beilstein J. Org. Chem. 2020, 16, 2119–2126, doi:10.3762/bjoc.16.179

• , spiropyranes, and stilbenes [2]. Diarylethenes were reported in the context of photoswitchable catalysis as inhibitors of the Karstedt´s catalyst [3] and for pKa modulation in acid–base-controlled processes [4]. Molecular motors for stereodivergent anion binding catalysis [5], azopeptides for the acetylation

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

• . In addition, the increased ring size could accommodate solvent molecules. Thus, an additional hindrance to anion binding could occur due to the need to displace solvent molecules. According to the computations, the rings formed by macrocycles starting from MC006 had sufficient size to fit anions

Anion-driven encapsulation of cationic guests inside pyridine[4]arene dimers

• Anniina Kiesilä,
• Jani O. Moilanen,
• Anneli Kruve,
• Christoph A. Schalley,
• Perdita Barran and
• Elina Kalenius

Beilstein J. Org. Chem. 2019, 15, 2486–2492, doi:10.3762/bjoc.15.241

• Berlin, Germany Michael Barber Centre for Collaborative Mass Spectrometry, Manchester Institute of Biotechnology, School of Chemistry, The University of Manchester, Princess Street, Manchester, UK 10.3762/bjoc.15.241 Abstract Pyridine[4]arenes have previously been considered as anion binding hosts due

• positive potential on the surface of the cavity, except on the N–H hydrogen atoms. They are, however, on tangential positions along the capsules surface, and therefore do not significantly contribute to anion binding [8]. More recently, we were also able to demonstrate that cationic transition metal

Small anion-assisted electrochemical potential splitting in a new series of bistriarylamine derivatives: organic mixed valency across a urea bridge and zwitterionization

• Keishiro Tahara,
• Tetsufumi Nakakita,
• Alyona A. Starikova,
• Takashi Ikeda,
• Masaaki Abe and
• Jun-ichi Kikuchi

Beilstein J. Org. Chem. 2019, 15, 2277–2286, doi:10.3762/bjoc.15.220

• intervalence charge transfer characteristics of the zwitterionic MV state. Keywords: anion binding; electrochemistry; hydrogen bonding; triarylamine; urea; zwitterionic mixed valency; Introduction Mixed-valence (MV) compounds have received increasing attention from the viewpoint of fundamental research on

1,2,3-Triazolium macrocycles in supramolecular chemistry

• Mastaneh Safarnejad Shad,
• Pulikkal Veettil Santhini and
• Wim Dehaen

Beilstein J. Org. Chem. 2019, 15, 2142–2155, doi:10.3762/bjoc.15.211

• results in the sensing of anions. In fact, strictly speaking this interaction is not a hydrogen bonding interaction seen as there is no X···H–Y unit (X, Y = O, N, F) but these interactions are often referred to as such in the literature. The anion binding can be enhanced by the alkylation of 1,2,3

• to be very difficult to further proceed. However, the anion binding property of the corresponding bistriazolium macrocyclic part 5·(BF4)2 (Figure 5) has successfully been investigated using 1H NMR titration experiments in CD3CN. The highest binding affinity was found to be almost similar for both BzO

• groups due to the anion binding, including chloride and other oxoanion salts. They also proved that the anions binding strength falls in line with their basicity as seen in the series AcO− > H2PO4− > Cl− > SO42− >NO3−. 2.5. 1,2,3-Triazolium macrocycles and [2]rotaxanes Supramolecular interactions could

Synthesis and anion binding properties of phthalimide-containing corona[6]arenes

• Meng-Di Gu,
• Yao Lu and
• Mei-Xiang Wang

Beilstein J. Org. Chem. 2019, 15, 1976–1983, doi:10.3762/bjoc.15.193

• investigate their anion binding behaviour. Taking compound 3a as a representative, we examined the interaction of macrocycles 3 with anions of tetra-n-butylammonium salts by means of electron spray ionization (ESI) mass spectrometry. It was found that the mass spectra of mixed samples of 3a with n-Bu4NX gave

Bambusuril analogs based on alternating glycoluril and xylylene units

• Tomáš Lízal and
• Vladimír Šindelář

Beilstein J. Org. Chem. 2019, 15, 1268–1274, doi:10.3762/bjoc.15.124

• with chromophore groups on their portals. However, the changes in the absorption spectra of these receptors upon anion binding were negligible since the groups on the portals were too distant from the anion binding site in the center of macrocycle. A different approach for the preparation of UV–vis

• -active bambusurils is based on the incorporation of the absorbing moiety directly into the macrocyclic framework. In such receptors, anion binding would take place in proximity of the chromophoric part of the macrocycle securing proper functioning of the sensor. Following this line, we decided to

• experiments. Unfortunately, both macrocycles 1a and 1b failed to act as an anion receptors due to their small cavities. Therefore, our future experiments will focus on further optimization of the reaction conditions and on the isolation of the three-membered macrocycle suitable for anion binding. Experimental

Design of a double-decker coordination cage revisited to make new cages and exemplify ligand isomerism

• Sagarika Samantray,
• Sreenivasulu Bandi and
• Dillip K. Chand

Beilstein J. Org. Chem. 2019, 15, 1129–1140, doi:10.3762/bjoc.15.109

• : anion binding; double-decker cage; ligand isomerism; macrocycles; palladium; self-assembly; supramolecular; Introduction Coordination-driven self-assembly is a convenient strategy for the construction of supramolecules of desired dimensions via simple synthetic procedures. Well-defined metal–ligand

• reported the first Pd2L4-type cage and the anion binding ability of the cavity [20]. They also used a non-chelating tridentate ligand in an attempt to prepare a Pd3L4-type double-decker coordination cage that would possess two cavities, if formed. However, the plan could not be executed as one of the

• tridentate ligand, i.e., pyridine-3,5-diylbis(methylene) dinicotinate (L1) is the focus of this work. In addition, the dynamic behavior as well as anion binding abilities of selected complexes are also probed. Ligand L1 is a constitutional isomer of ligand L2 [22][23] and is expected to exhibit similarities

Silanediol versus chlorosilanol: hydrolyses and hydrogen-bonding catalyses with fenchole-based silanes

• Falco Fox,
• Jörg M. Neudörfl and
• Bernd Goldfuss

Beilstein J. Org. Chem. 2019, 15, 167–186, doi:10.3762/bjoc.15.17

• catalytic and anion binding characteristics. Results and Discussion Enantiopure dichlorosilane 7 is readily accessible by lithiation of BIFOL (5) [28][52][54][59] and subsequent reaction with tetrachlorosilane (92% yield, Scheme 2). Unlike the hydrolysis of BIFOP-Cl (6) to BIFOP-OH, the dichlorosilane 7 is

• %) for chloride is determined, which is in the same order as di(1-naphthyl)silanediol (1, Figure 1) with 4688.0 M−1 (5%, Table 6). The binding constant of chlorosilanol 8 (Figure 13) for chloride is 451.1 M−1 (4%). Thus chlorosilanol 8 and silanediol 9 are feasible for anion binding of chloride. Counter

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

• . More specifically, both octacarboxylate 1 and positand 2 have a non-polar cavity that can function as an anion (but not to our knowledge a cation) binding site. Anion binding to the cavity of positively charged 2 is stronger than to negatively charged 1 [13][14], but nevertheless anion binding to 1 can

• be as strong as 4.60 kcal mol−1. Host 2 has a second anion binding site in the form of the crown of trimethylammoniums “under” the primary bowl [14], and correspondingly the four chelating carboxylates of the crown of 1 may be a reasonable cation binding site. Furthermore, in addition to these

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

• publications have been reported about receptors that more effectively interact with less charged nucleotides. For instance, Kuchelmeister et al. synthesized a receptor with two symmetric peptide arms decorated with guanidinium-based anion binding sites. This receptor showed a stronger binding of AMP in

p-tert-Butylthiacalix[4]arenes functionalized by N-(4’-nitrophenyl)acetamide and N,N-diethylacetamide fragments: synthesis and binding of anionic guests

• Alena A. Vavilova and
• Ivan I. Stoikov

Beilstein J. Org. Chem. 2017, 13, 1940–1949, doi:10.3762/bjoc.13.188

• receptor. In contrast to the 1,3-disubstituted macrocycle containing two N-(4’-nitrophenyl)acetamide moieties, the 1,2-disubstituted thiacalix[4]arene, which contains only one such fragment and a N,N-diethylacetamide moiety, selectively binds F− anions. Keywords: anion binding; synthesis; thiacalixarenes

• ,N-diethylacetamide fragment and its further functionalization with the N-(4’-nitrophenyl)acetamide moiety. We also calculated the proposed model of anion binding for the new and previously synthesized thiacalix[4]arenes and compared their complexation properties toward number of singly charged

• (phenolic fragments) groups can participate in anion binding. To determine the possibility of the tetrabutylammonium cation binding by the synthesized thiacalix[4]arenes, solutions of the compounds 3, 5 and 6 in the presence of a 10-fold excess of n-Bu4NX (X = F−, Cl−, Br−, I−, CH3CO2−, H2PO4−, NO3−) were

Mechanochemical synthesis of thioureas, ureas and guanidines

• Vjekoslav Štrukil

Beilstein J. Org. Chem. 2017, 13, 1828–1849, doi:10.3762/bjoc.13.178

• reactive in the amination reaction. Ureas Just as thioureas are typically synthesized by coupling reaction between amines and isothiocyanates, ureas as oxygen analogues are prepared from the corresponding isocyanates. This approach was employed in the synthesis of anion binding 1-(pyridin-3-yl)-3-p

• ) The proposed synthesis of monosubstituted thioureas 32. b) Conversion of N-thiocarbamoyl benzotriazole 27d to thiourea 32d by aging in ammonia vapours. A few examples of mechanochemical amination of thiocarbamoyl benzotriazoles by in situ generated ammonia. Mechanochemical synthesis of a) anion

• binding urea 33 by amine-isocyanate coupling and b) dialkylurea 34 by alkylation of unsubstituted urea. a) Solvent-free milling synthesis of the bis-urea anion sensor 35. b) Non-selective desymmetrization of o-pda with phenyl isocyanate. c) Different reactivity of mono-thiourea 19b and mono-urea 36 under

Spectral and DFT studies of anion bound organic receptors: Time dependent studies and logic gate applications

• Srikala Pangannaya,
• Neethu Padinchare Purayil,
• Shweta Dabhi,
• Venu Mankad,
• Prafulla K. Jha,
• Satyam Shinde and
• Darshak R. Trivedi

Beilstein J. Org. Chem. 2017, 13, 222–238, doi:10.3762/bjoc.13.25

• for F− and AcO– ions allowing the real time analysis of these ions in aqueous media. The formation of the receptor–anion complexes has been supported by UV–vis titration studies and confirmed through binding constant calculations. The anion binding process follows a first order rate equation and the

• ][24][25][26]. The choice of the appropriate detection technique is highly essential as it directly dictates the efficacy of the sensor. Anion binding through colorimetric probes comprising of a binding site and a signaling unit works in a coordinative way yielding an optical output visible to the

• response of the anion detection process. The anion binding properties of receptors R1 and R2 (4.5 × 10−5 M in DMSO), have been studied through the addition of 2 equiv of a series of anions as their tetrabutylammonium salts (F−, Cl−, Br−, I−, NO3−, HSO4−, H2PO4− and AcO− at concentrations of 1 × 10−2 M in