Unraveling cooperative interactions between complexed ions in dual-host strategy for cesium salt separation

• Zhihua Liu,
• Ya-Zhi Chen,
• Ji Wang,
• Qingling Nie,
• Wei Zhao and
• Biao Wu

Beilstein J. Org. Chem. 2025, 21, 845–853, doi:10.3762/bjoc.21.68

• binding Na+ and K+ by oligourea foldamers and macrocycles [37][38][39]. However, in the solid−liquid extraction of Li2SO4 in DMSO, addition of crown ether did not help to increase the extraction efficiency. This is because ion-dipole interactions are negligible in high polar solvent, and Li+ binding is

• to be slightly upfield-shifted in comparison to that of the free crown ether, indicating Cs+ binding, consistent with their extraction efficiency. The relatively upfield shifted chemical shift for the Cs3PO4 complex may indicate strong cooperative interaction upon solid–liquid extraction. To

Recent advances in allylation of chiral secondary alkylcopper species

• Minjae Kim,
• Gwanggyun Kim,
• Doyoon Kim,
• Jun Hee Lee and
• Seung Hwan Cho

Beilstein J. Org. Chem. 2025, 21, 639–658, doi:10.3762/bjoc.21.51

• otherwise predominant β-F elimination from the α-CF3-alkylcopper intermediate 39. Detailed kinetic studies confirmed the effect of the crown ether. When KOPiv was employed alone, the initial rate of defluorination increased by 1.57-fold, whereas the addition of 18-crown-6 reduced this acceleration to 1.22

• -fold. These observations supported the hypothesis that the crown ether effectively disrupts the interaction between the alkali metal cation and fluorine atom, thereby decreasing the rate of β-F elimination. This asymmetric copper-catalyzed protocol represents one of the rare examples that allows to

Binding of tryptophan and tryptophan-containing peptides in water by a glucose naphtho crown ether

• Gianpaolo Gallo and
• Bartosz Lewandowski

Beilstein J. Org. Chem. 2025, 21, 541–546, doi:10.3762/bjoc.21.42

• binding of tryptophan is therefore important for diagnostic and medicinal applications. Recently, we reported a glucose naphtho crown ether which is a chemoselective receptor for the esters of aromatic amino acids, in particular tryptophan, in water. Herein, we demonstrate that the same compound also

• aqueous media is limited (Figure 1a–c) [13][14][15][16][17][18]. In particular, receptors which bind tryptophan residues in peptides are rare [19][20]. Recently, we developed a glucose-based naphtho crown ether 1 (Figure 1d) which binds amino acid methyl esters with aromatic side chains chemoselectively

• in water [21]. Crown ether 1 is particularly suited for the sensing of Trp methyl ester, which it binds with a higher affinity than the Phe and Tyr esters. Additionally, the binding of Trp-OMe results in a highly efficient fluorescence quenching of the naphthalene unit in the receptor. Herein, we

Cyclodextrin-based rotaxanes for polymer materials: challenge on simultaneous realization of inexpensive production and defined structures

• Yosuke Akae

Beilstein J. Org. Chem. 2024, 20, 3026–3049, doi:10.3762/bjoc.20.252

• such stimuli. When the rotaxane motif contains cyclophane or a crown ether, stimuli induced by a transition metal or an electrostatic interaction have been widely used. These interactions are easily controlled, and they induce relatively strong coordination interactions among the components, making

• acceptable to reduce the production costs, suggesting the industrial potential of this random modification protocol. As suggested by the recent study on the RCP made of crown ether-based [3]rotaxane crosslinker, the force distribution effect worked sufficiently to toughen RCPs, even when the translation

Synthetic applications of the Cannizzaro reaction

• Bhaskar Chatterjee,
• Dhananjoy Mondal and
• Smritilekha Bera

Beilstein J. Org. Chem. 2024, 20, 1376–1395, doi:10.3762/bjoc.20.120

• Rouser et al. using an intramolecular Cannizzaro reaction to give the corresponding unsymmetrical acid–alcohol substituted crown ether derivatives 43–46. Good to excellent yields of the desymmetrized Cannizarro products 43–46 were obtained using Ba(OH)2 as the base, thus effecting efficient

• desymmetrization of crown ether dialdehydes (Scheme 17) [84]. Synthesis of natural products and pharmaceuticals Exploring intramolecular Cannizzaro reaction: The Cannizzaro reaction is a versatile synthetic tool with applications in the synthesis of natural products, fine chemicals, and pharmaceuticals. Its

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

• podand unit adopts a cyclic conformation wrapping around the cation and brings the arms close to each other. The selectivity of the cation binding can be modulated by changing the chain length similarly to a crown ether (Figure 17). The cation can be removed by the addition of a better ligand such as a

• crown ether. The authors reported switchable tweezers bearing metalloporphyrin arms that can be switched by the addition of K+ and Na+ cations. The cation brings the porphyrins together and causes some dynamic fluorescence quenching from the iodine counter anion. The authors attributed the more

• cooperative catalytic effect of the two Cr(III) units. Control experiments without K+, or in the presence of competitive crown ether presented a reduced conversion rate and enantioselectivity, proving the conformation change in the reactivity of the system. Anion responsive tweezers The main types of anion

Active-metal template clipping synthesis of novel [2]rotaxanes

• Cătălin C. Anghel,
• Teodor A. Cucuiet,
• Niculina D. Hădade and
• Ion Grosu

Beilstein J. Org. Chem. 2023, 19, 1776–1784, doi:10.3762/bjoc.19.130

• presence of supramolecular interactions that pre-organize rotaxane’s components is crucial for an efficient synthesis. The precursors of rotaxanes are supramolecular architectures held together by numerous interactions leading to diverse motifs such as ammonium crown ether (ion-dipole, hydrogen bonding

Tying a knot between crown ethers and porphyrins

• Maksym Matviyishyn and
• Bartosz Szyszko

Beilstein J. Org. Chem. 2023, 19, 1630–1650, doi:10.3762/bjoc.19.120

• Maksym Matviyishyn Bartosz Szyszko Faculty of Chemistry, University of Wrocław, 14 F. Joliot-Curie St., 50-383 Wrocław, Poland 10.3762/bjoc.19.120 Abstract Porphyrins and crown ether hybrids have emerged as a promising class of molecules composed of elements of a tetrapyrrole macrocycle and an

• oligo(ethylene glycol) segment. These hybrid systems constitute a broad group of compounds, including crowned porphyrins, crownphyrins, and calixpyrrole-crown ether systems forming Pacman complexes with transition metals. Their unique nature accustoms them as excellent ligands and hosts capable of

• metals. In this perspective article, the overview of both the early designs of porphyrin-crown ether hybrids, as well as the most recent advances in the synthesis and characterisation of this remarkable group of macrocyclic systems, are addressed. The discussion covers the strategies employed in

Light-responsive rotaxane-based materials: inducing motion in the solid state

• Adrian Saura-Sanmartin

Beilstein J. Org. Chem. 2023, 19, 873–880, doi:10.3762/bjoc.19.64

• different flexibility. The crown ether derivative acts as a chassis in order to fix the thread. A ferrocenyl group attached at one of the ends of the linear component serves as a photosensitizer allowing the absorption of visible light. The different substitution induced different types of deformations

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

• ][36][37][38], anion templates [39][40], ammonium crown ether templates [41], and templates based on π–π interactions [42]. In 2004, Sauvage and co-workers have used a Cu(I)-based passive metal template approach to synthesize a [2]catenane containing an optically pure BINOL unit in each macrocycle [43

• -ray analysis revealed the presence of the expected [N–H···O] hydrogen bonds between the secondary ammonium station and the crown-ether macrocycle, but also additional [C–H···O] hydrogen bonds involving the benzylammonium methylene groups (see Figure 4). Interestingly, the presence of the directional

• supramolecular template strategies that have been developed in the past decades, including passive metal templates, active metal templates, anion templates, ammonium crown ether templates, and templates based on π–π interactions. This has opened the way for the application of the resulting chiral MIMs. The

Regioselective N-alkylation of the 1H-indazole scaffold; ring substituent and N-alkylating reagent effects on regioisomeric distribution

• Ryan M. Alam and
• John J. Keating

Beilstein J. Org. Chem. 2021, 17, 1939–1951, doi:10.3762/bjoc.17.127

• was carried out, using 1 equivalent of the ether 15-crown-5 (with respect to NaH) (Table 5). Chelation of the sodium cation with the crown ether should disrupt the formation of tight ion pairs (Scheme 2) and attenuate N-1 regioselectivity. The presence of 15-crown-5 caused a notable reduction in N-1

• regioselectivity, when compared with results obtained in the absence of the crown ether (ratio N-1 (10):N-2 (11) = 9.6:1 (Table 5, entry 1) versus > 99:1 (Table 1, entry 22)). Similarly, to disqualify any potential inherent effect of the crown ether on the regioselective outcome, increasing the number of

[2 + 1] Cycloaddition reactions of fullerene C₆₀ based on diazo compounds

• Yuliya N. Biglova

Beilstein J. Org. Chem. 2021, 17, 630–670, doi:10.3762/bjoc.17.55

• 35 [92] and 36–38 (Figure 4) [93]. A synthesis based on benzo-18-crown-6 to give 39 showed that attachment of the crown ether to the surfaces of fullerene molecules makes it easier to detect them by mass spectrometry [94]. This method was used to incorporate benzocrown ether residues in order to

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

• can easily gain information on host–guest interactions in supramolecular systems as well as the photocatalytic reaction efficiency. Review Macrocycle-promoted photocatalysis Photocatalysis based on crown ethers and crown ether derivatives CEs are a class of macrocycles that consist of a ring with a

• repeating unit. The term "crown" is derived from the resemblance of the crown ether when bound to a cation with a crown sitting on a head. The most common crown ethers are those of ethylene oxide. The exterior of the ring is hydrophobic, while the oxygen atoms within the ring can strongly coordinate to a

• of functional photocatalytic systems [16][17]. The diversity of crown ether-based photocatalytic reactions is relatively low, involving mainly photocycloaddition reactions. Saltiel and co-workers reported the regiospecific intermolecular [2 + 2]-photocycloaddition based on a supramolecular assembly

Using multiple self-sorting for switching functions in discrete multicomponent systems

• Amit Ghosh and
• Michael Schmittel

Beilstein J. Org. Chem. 2020, 16, 2831–2853, doi:10.3762/bjoc.16.233

• chemical stimuli yielding different supramolecular products. The porphyrin ligands of the cage [Zn4(8')6]8+ interacted favorably with C70 as a guest, whereas an electron-rich aromatic crown-ether did thread onto the electron-deficient naphthalene diimides of cage [Zn4(7')6]8+ forming mechanically

• addition of zinc(II), the silver(I) ions were translocated as a second messenger from the nanoswitch [Ag(35)]+ to the anthracene-appended crown ether 36 in a 2-fold completive self-sorting, i.e., furnishing [Zn(35)]2+ and [Ag(36)]+ (state SelfSORT-II). In this state, SelfSORT-II, the emission emerged at

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

• with a complementary base sequence [10], the AuNPs with peripheral carboxylate groups introduced by the Hupp group [11] that responded to divalent transition metal ions, or Chen at al.’s crown ether-decorated AuNPs that allowed the sensing of potassium ions [12]. Numerous other such probes have been

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

• corresponding free macrocycle. The detailed understanding of the thermodynamic and electrochemical properties of the tailor-made crown ethers lays the foundation for the construction of new types of molecular redox switches with emergent properties. Keywords: crown ether; isothermal titration calorimetry

• ; redox chemistry; rotaxanes; supramolecular chemistry; Introduction Pedersen discovered crown ethers in 1967 while searching for multidentate ligands for the vanadyl group [1][2][3]. He was later awarded the Nobel Prize in Chemistry for his studies on the crown ether selective binding properties towards

• alkali metal ions [2]. Crown ethers and their binding properties nowadays find frequent application, e.g., as cation sensors [4][5][6][7], as phase-transfer catalysts [8][9][10], or as drug delivery systems [11][12][13]. Already at the early stages of crown ether research, considerable effort has been

A green, economical synthesis of β-ketonitriles and trifunctionalized building blocks from esters and lactones

• Daniel P. Pienaar,
• Kamogelo R. Butsi,
• Amanda L. Rousseau and
• Dean Brady

Beilstein J. Org. Chem. 2019, 15, 2930–2935, doi:10.3762/bjoc.15.287

• solvent is effectively lowered by adding a small amount of polar, protic IPA and this facilitates acetonitrile deprotonation. Alternatively, the addition of a crown ether is also known to enhance nucleophilic substitution reaction rates, but in this case through the suppression of ion-pairing [16]. We

• ether (MTBE) with 0.1 equiv IPA as co-solvent/additive, a significantly higher yield of 18 was obtained when we used 10 mol % 18-crown-6 ether instead of IPA in a similarly catalytic amount. The yield was further improved to 67% using 2MeTHF as the solvent. It should be noted that the use of the crown

• ether resulted in recovery complications for some of the other compounds (e.g., when this methodology was applied to δ-valerolactone and γ-butyrolactone) and may therefore not be universally beneficial. Conclusion In conclusion, mild, environmentally friendly procedures were developed for the

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

• (DB24C8) are capable of a reversible pH-controlled movement of the crown ether between two stations. UV–vis absorption spectroscopy experiments and 1H NMR spectroscopy have shown that the electron-rich crown ether rings and the electron-deficient N-methyl-1,2,3-triazolium can interact with each other

• the 1H NMR spectra or color changes, upon addition of DIEA to the corresponding triazole analogue (precursor to 17a) because of only weak interaction between the crown ether and the triazole unit. This clearly proves the importance of the triazolium moiety for the switching process. Color changes with

• catenane 17b upon addition of base were less noticeable because of a weaker CT band in the case of a dibenzo-fused crown ether. Thus, the authors have proven that the movement of macrocyclic rings within catenanes can be controlled by switching the pH, and the bisnaphtho crown ethers can act either as

Tautomerism as primary signaling mechanism in metal sensing: the case of amide group

• Vera Deneva,
• Georgi Dobrikov,
• Aurelien Crochet,
• Daniela Nedeltcheva,
• Katharina M. Fromm and
• Liudmil Antonov

Beilstein J. Org. Chem. 2019, 15, 1898–1906, doi:10.3762/bjoc.15.185

• stability constants upon complexation, the selectivity is rather low, which can be attributed to the crown ether complexation features in general. Developing the system further, leads to modification of the ionophore part by replacing the crown ether with other ionophores, such as done in the case of 4 and

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

• absorption and fluorescence spectra of these PDI/NDI derivatives in different solvents as well as their morphologies were investigated. Keywords: aqueous medium; crown ether; macrocycle; perylene diimide derivative; self-assembly; Introduction Owing to their unique physicochemical properties, self

• macrocyclic hosts, crown ethers, have been widely used as building blocks for supramolecular assemblies in the past two decades [37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53], mainly in the fabrication of crown ether-based threaded or interlocked assemblies in organic solvents [54

• , little was known to the self-assembly behaviors of B21C7 crown macrocycle functionalized PDIs/NDIs in aqueous solution, even though there have been several reports about crown ether-functionalized PDIs or NDIs, which mostly focused on their interactions with metal ions [82][83][84][85]. Herein, we

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

• Abstract Four benzothiazolium crown ether-containing styryl dyes were prepared through an optimized synthetic procedure. Two of the dyes (4b and 4d) having substituents in the 5-position of the benzothiazole ring are newly synthesized compounds. They demonstrated a higher degree of trans–cis

• -crown-5 ether; benzothiazolium crown ether-containing styryl dyes; E/Z photoisomerization; molecular solar thermal system; Introduction Molecular photoswitches permanently attract considerable interest because they hold potential for application in molecular electronic and photonic devices [1][2][3][4

• improvements and brings the scientists nearer to the identification of the “perfect” MOST system. In this connection we identified crown ether-containing styryl dyes [14][15] as promising substances due to their ability to undergo trans-to-cis photoisomerization (E/Z) with very high quantum yields. In addition

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

• Krzysztof M. Zwolinski Julita Eilmes Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387 Kraków, Poland 10.3762/bjoc.15.57 Abstract The first crown ether-capped dibenzotetraaza[14]annulenes (DBTAAs), featuring two macrocyclic binding sites fixed in a face-to-face orientation

• -ATR, 1H and 13C NMR spectroscopy and elemental analysis. Keywords: crown ether; dibenzotetraaza[14]annulene; DBTAA; macrocycle; Schiff base; Introduction The design and synthesis of novel polycyclic receptor architecture is of fundamental importance, since model recognition studies contribute to

• towards the cationic organic species [4] and ions of certain metal elements [5]. Particulary, synthetic receptors featuring crown ether moieties often equipped with extra side arms bearing pendant functional groups [6][7], have attracted a great deal of interest due to their outstanding binding ability

LCST phase behavior of benzo-21-crown-7 with different alkyl chains

• Yan Deng,
• Xing Li,
• Qiao Zhang,
• Zheng Luo,
• Chengyou Han and
• Shengyi Dong

Beilstein J. Org. Chem. 2019, 15, 437–444, doi:10.3762/bjoc.15.38

• are provided in Supporting Information File 1, Figures S1–S34). Crown ethers with hydroxy groups (2) or amine groups (4) were prepared according to reported methods [42]. Hydrophobic alkyl chains with different lengths and branching were connected to the crown ether through condensation reactions

• , when the concentration was kept the same for both samples (15 mg/mL). Consistent with reported crown ether systems [39], 3a–d showed small hysteresis (around 2.0 °C) during heating and cooling cycles, indicating the chemical integrity during tests (Figure S36–S39, Supporting Information File 1

• measurements. For 3b–d, not only changes in chemical shifts but also new peaks were found, when the temperature was higher than the compounds’ Tcloud, which is similar to 3a. However, compared with thermo-responsiveness of 3a–d, 5d is the only crown ether among the urea-based series 5a–e, showing LCST behavior

First synthesis of cryptands with sucrose scaffold

• Patrycja Sokołowska,
• Michał Kowalski and
• Sławomir Jarosz

Beilstein J. Org. Chem. 2019, 15, 210–217, doi:10.3762/bjoc.15.20

• -chloroethyl) ether; this process provided an intermediate 9 in good yield. Replacement of both terminal chlorine atoms by iodine afforded compound 10, which was reacted with commercially available diaza-crown ether 8 to afford the first sucrose cryptand 11 in excellent yield (33%, Scheme 1). The structure of

• . This goal can be realized starting from sucrose triol 2 as shown in Figure 3. The first approach consists of a connection of the C1’-position of an intermediate aza-crown ether 12 with the secondary nitrogen atom present in a linker (route a in Figure 3). Another one (route b in Figure 3) involves a

Synthesis of a leopolic acid-inspired tetramic acid with antimicrobial activity against multidrug-resistant bacteria

• Luce Mattio,
• Loana Musso,
• Leonardo Scaglioni,
• Andrea Pinto,
• Piera Anna Martino and
• Sabrina Dallavalle

Beilstein J. Org. Chem. 2018, 14, 2482–2487, doi:10.3762/bjoc.14.224

• to rt, 1 h, 8a: 81%, 8b: 66%; e) dodecanoyl chloride, TEA, CHCl3, 0 °C to rt, 3 h, 90%; f) t-BuOK 1 M in THF, THF, reflux, 1.5 h, 65%; g) benzyl tosylate, KHMDS 0.5 M in toluene, crown ether 18-crown-6, THF, 0 °C to rt, 3 h, 35%; h) TFA, 60 °C, 2h; i) CAN, CH3CN/H2O (3:1), 0 °C to rt, 1h; j) benzyl

• tosylate, KHMDS 0.5 M in toluene, crown ether 18-crown-6, THF, 0 °C to rt, 2.5 h, 30% over two steps. Synthesis of dipeptide L-Phe-L-Val intermediate 20. Reagents and conditions: a) PTSA·H2O, benzyl alcohol, toluene, reflux, 10 h, 70%; b) HClO4, tert-butyl acetate, 0 °C, 1 h, then rt, 20 h, 75%; c