Dicarboxylate recognition based on ultracycle hosts through cooperative hydrogen bonding and anion–π interactions

• Wen-Hui Mi,
• Teng-Yu Huang,
• Xu-Dong Wang,
• Yu-Fei Ao,
• Qi-Qiang Wang and
• De-Xian Wang

Beilstein J. Org. Chem. 2025, 21, 884–889, doi:10.3762/bjoc.21.72

• obtained using either 1:1 or 1:2 binding models. This is likely due to their intermediate size of chain lengths, which are neither long enough for 1:1 binding nor capable of squeezing a dimer for 1:2 complexation. Notably, the unsubstituted ultracycle B4 [31] without the pendant OH groups on the lower rim

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

• by adding carbonate (in the form of 18-crown-6 complexed Cs2CO3) showing slow-exchange of NMR signals (DMSO-d6, [1] = [salts] = 1 mM, 400 MHz, 298 K). (c) Fitted binding curve of carbonate complexation with receptor L as derived from NMR titration. (a) Single crystal structure of complexed Cs3PO4

Chitosan-supported CuI-catalyzed cascade reaction of 2-halobenzoic acids and amidines for the synthesis of quinazolinones

• Xuhong Zhao,
• Weishuang Li,
• Mengli Yang,
• Bojie Li,
• Yaoyao Zhang,
• Lizhen Huang and
• Lei Zhu

Beilstein J. Org. Chem. 2025, 21, 839–844, doi:10.3762/bjoc.21.67

• , which acts as a base. Subsequently, I undergoes oxidative addition and complexation with the amidine 2 to generate intermediate II. This intermediate then undergoes reductive elimination to form intermediate III, releasing CS@CuI back into the system. Finally, the coupling reaction between the carboxyl

Development and mechanistic studies of calcium–BINOL phosphate-catalyzed hydrocyanation of hydrazones

• Carola Tortora,
• Christian A. Fischer,
• Sascha Kohlbauer,
• Alexandru Zamfir,
• Gerd M. Ballmann,
• Jürgen Pahl,
• Sjoerd Harder and
• Svetlana B. Tsogoeva

Beilstein J. Org. Chem. 2025, 21, 755–765, doi:10.3762/bjoc.21.59

• provides (together with the similarly exothermic complexation of calcium complex 7 with hydrazone) driving force for the catalytic cycle, but, on the other hand, may impede enantioselectivity, because of a "backwater" effect equaling out outcomes from different reaction pathways before intermediates are

Acyclic cucurbit[n]uril bearing alkyl sulfate ionic groups

• Christian Akakpo,
• Peter Y. Zavalij and
• Lyle Isaacs

Beilstein J. Org. Chem. 2025, 21, 717–726, doi:10.3762/bjoc.21.55

• spectroscopic characterization of C1 along with determination of its inherent aqueous solubility and self-association properties. Next, we present the X-ray crystal structure of C1 as its C1·Me6CHDA complex. Subsequently, we describe a qualitative investigation of C1·guest and M1·guest complexation by 1H NMR

• spectroscopy and quantitative investigation by isothermal titration calorimetry (ITC). Finally, we discuss the trends in binding affinity observed for C1·guest and M1·guest complexation. Design, synthesis and characterization of C1 In order to disentangle the effects of the ionic group (sulfonate versus

• ). Qualitative study of C1·guest recognition properties by 1H NMR spectroscopy Next, we decided to perform a qualitative investigation of the host–guest properties of C1 by 1H NMR spectroscopy. Figure 3 shows the chemical structures of a panel of guests that were studied and the complexation-induced changes in

Origami with small molecules: exploiting the C–F bond as a conformational tool

• Patrick Ryan,
• Ramsha Iftikhar and
• Luke Hunter

Beilstein J. Org. Chem. 2025, 21, 680–716, doi:10.3762/bjoc.21.54

Quantifying the ability of the CF₂H group as a hydrogen bond donor

• Matthew E. Paolella,
• Daniel S. Honeycutt,
• Bradley M. Lipka,
• Jacob M. Goldberg and
• Fang Wang

Beilstein J. Org. Chem. 2025, 21, 189–199, doi:10.3762/bjoc.21.11

• Reichardt's dye [53][54][55] as an indicator. These experiments measure the blue shift of Reichardt's dye upon complexation with an HB donor (Figure 3A, and Figures S13–S18 in Supporting Information File 1), from which the dissociation constant (Kd) of the HB complex can be determined. A smaller Kd value

• technique can be employed as a general approach for quantifying the energetics of HB interaction-enabled binding processes. Additionally, the free energies of HB complexation calculated at the PCM(MeCN)-M06-2X/6-31+G(d,p) level correlate well with our experimental data, allowing for binding affinity

Hydrogen-bonded macrocycle-mediated dimerization for orthogonal supramolecular polymerization

• Wentao Yu,
• Zhiyao Yang,
• Chengkan Yu,
• Xiaowei Li and
• Lihua Yuan

Beilstein J. Org. Chem. 2025, 21, 179–188, doi:10.3762/bjoc.21.10

• ., metal coordination interactions and hydrogen bonding), providing access to various multiresponsive orthogonal self-assemblies or smart supramolecular polymers [24][25]. For example, the discovery of cucurbit[8]uril complexation in a 1:2 and 2:2 host–guest stoichiometry leads to a wide spectrum of

• between hydrogen atoms of G1 and the nearby phenyl groups of H2, with a distance of 2.7–2.9 Å (Figure 3a and Figure 3b). These results provided conclusive evidence for the 2:2 recognition mode through interaction of two guests with two macrocycles. With the 2:2 host–guest complexation pattern in mind, a

• coordinating metal ions. In such supramolecular polymers, orthogonal host–guest and coordination interactions are responsible for polymerization. Host–guest complexation and zinc coordination When forming supramolecular polymers, an AB-type monomer, i.e., the guest G2, is supposed to interact with the

Cu(OTf)₂-catalyzed multicomponent reactions

• Sara Colombo,
• Camilla Loro,
• Egle M. Beccalli,
• Gianluigi Broggini and
• Marta Papis

Beilstein J. Org. Chem. 2025, 21, 122–145, doi:10.3762/bjoc.21.7

• dual activity as a metal catalyst as well as a Lewis acid [8][9][10][11]. However, in many cases, the role of copper is not clear and both activities often work synergistically. In all other cases, copper’s activity is due to the coordination/complexation with unsaturated systems, but it is rarely

• to multiple C–C bonds generates extended carbon radicals capable of giving further functionalization. Regarding the ionic mechanism, the key step generally comprises the complexation with the unsaturated substrate leading to activation of the alkenyl/alkynyl moiety towards a nucleophilic attack. In

Tailored charge-neutral self-assembled L₂Zn₂ container for taming oxalate

• David Ocklenburg and
• David Van Craen

Beilstein J. Org. Chem. 2024, 20, 3007–3015, doi:10.3762/bjoc.20.250

• ready receptor preparation by metal complexation. The reason for the underrepresentation is the competitive nature and excellent ligand properties of oxalate which not only is associated with the aforementioned diseases but also poses a serious hazard for metal-driven self-assemblies because the dianion

• conjugated base of the smallest dicarboxylic acid, stands out from the list of highly relevant analytes because oxalic acid is found in common edible plants and its corresponding dianion is tied to several diseases, e.g., the formation of kidney stones through complexation of calcium and precipitation of

• acetate salt results in a charge-neutral and bench-stable [L2Zn2] metallocontainer. Purification of the complex is achieved by lyophilization which accomplishes the removal of acetic acid as only byproduct of the complexation reaction and DMSO as solvent. The charge-neutral receptor is obtained as a

Diameter-selective extraction of single-walled carbon nanotubes by interlocking with Cu-tethered square nanobrackets

• Guoqing Cheng and
• Naoki Komatsu

Beilstein J. Org. Chem. 2024, 20, 1298–1307, doi:10.3762/bjoc.20.113

• square nanobrackets, is designed, synthesized and applied to single-walled carbon nanotubes (SWNTs) for their diameter-based separation. The complexation between copper ions and dipyrrin moieties of the nanobracket gives Cu-tethered square nanobrackets, which is confirmed by absorption, Raman and MALDI

• diameter range. The diameter selectivity is supported by the theoretical calculations with the GFN2-xTB method, indicating that the most preferred SWNT diameter for the square Cu-nanobrackets is 1.04 nm. Keywords: complexation; diameter; extraction; interlock; nanobracket; single-walled carbon nanotubes

• complexation between host molecules and SWNTs are strongly related to the molecular structures, making it possible to tune the binding affinity [8]. The host molecules we employed so far for CNT separation through molecular recognition have been developed as “nanotweezers” [9], “nanocalipers” [10] and

Three-component N-alkenylation of azoles with alkynes and iodine(III) electrophile: synthesis of multisubstituted N-vinylazoles

• Jun Kikuchi,
• Roi Nakajima and
• Naohiko Yoshikai

Beilstein J. Org. Chem. 2024, 20, 891–897, doi:10.3762/bjoc.20.79

• this conjecture, the present reaction is proposed to involve reversible complexation between the alkyne and the cationic iodine(III) electrophile and subsequent trans-addition of the azole nucleophile, the latter step being coupled with concomitant deprotonation of the N–H bond by the triflate anion

Synthesis and characterization of water-soluble C₆₀–peptide conjugates

• Yue Ma,
• Lorenzo Persi and
• Yoko Yamakoshi

Beilstein J. Org. Chem. 2024, 20, 777–786, doi:10.3762/bjoc.20.71

• either 1) covalent functionalization of the fullerene surface with polar moieties or 2) complexation with water-soluble host molecules or polymers. Related to the former approach, the Nakamura group [11], Wudl group [12], and Hirsch group [13] reported initial work in the early 1990s on water-soluble C60

• solubility [14][15]. As early examples of the latter approach in the 1990s, Wennerström and co-workers reported the study of supramolecular BiCAP complexation of C60 with γ-cyclodextrin (γ-CD) [16]. Shinkai and co-workers synthesized water-soluble calixarene derivatives to form water-soluble complexes with

• C60 [17][18]. By either chemical functionalization or complexation of the fullerene core, a number of biocompatible fullerene materials with interesting biological activities were recently prepared and reported [19][20][21][22][23][24]. We have reported water-soluble complexes of C60 with a nontoxic

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

• -workers introduced a switchable system based on a terpyridine (terpy) ligand (Figure 8), which is structurally similar to the diphenylpyridine units used by Zimmerman in rigid clips, but can change their conformation upon complexation by a metal cation [32][33]. When substituted at the 6 and 6" positions

• host–guest complexation, it can also only bind to coordinating guests (terpyridine, bipyridine) due to the proximity of the coordination sphere with the binding pocket. Tweezers 11 with NDI arms and an extended pyridine-hydrazone-pyridine-hydrazone-pyridine switchable unit have thus been developed

• coordination-switchable tweezers for switching between two magnetic states that are stable at room temperature [44]. To increase the magnetic coupling between the metal center the group investigated the Mn(III)–salphen tweezers 14 that can coordinate in apical position to cyanide ions. The complexation of CN

Enhanced host–guest interaction between [10]cycloparaphenylene ([10]CPP) and [5]CPP by cationic charges

• Eiichi Kayahara,
• Yoshiyuki Mizuhata and
• Shigeru Yamago

Beilstein J. Org. Chem. 2024, 20, 436–444, doi:10.3762/bjoc.20.38

• applying high pressure (6 GPa) in the complexation between [9]CPP and C60 [42]. In these examples, partial charge transfer (CT) from the CPP host to the guest was observed, but the degree of CT was limited. Furthermore, no clear effects of CT on the physical properties have been reported. We have already

• 1H NMR titration experiments (see Supporting Information File 1, Figure S1), indicating that the complexation was exergonic with a ΔG = −19 kJ mol−1. This value is about 20 times higher than that of the neutral complex, [10]CPP⊃[5]CPP (Ka = 0.053 × 103 L·mol−1 in TCE-d2 at 50 °C, ΔG = −11 kJ mol−1

• ) [31]. The increased Ka is most likely attributed to the ionic interaction caused by the presence of the cationic species, as will be discussed below. To clarify the effect of the polar interaction, the host–guest complexation was studied in a polar solvent, such as nitrobenzene and acetonitrile

Spatial arrangements of cyclodextrin host–guest complexes in solution studied by ¹³C NMR and molecular modelling

• Konstantin Lebedinskiy,
• Ivan Barvík,
• Zdeněk Tošner,
• Ivana Císařová,
• Jindřich Jindřich and
• Radim Hrdina

Beilstein J. Org. Chem. 2024, 20, 331–335, doi:10.3762/bjoc.20.33

• crystallization of host–guest complexes and their crystallographic analysis. Keywords: anisotropy; 13C NMR; cyclodextrin; host–guest complexes; Introduction Complexation of organic and inorganic compounds with α-, β-, or γ-cyclodextrins and their derivatives [1] is an established tool used in medicine for drug

• peaks of all prochiral carbon signals of the guest upon complexation with α-CD. The biggest split, 22.5 Hz, was observed for prochiral carbons 8 and 10, depicted in Figure 1 in green color, followed by a split of carbons 3 and 9 (in blue color) and the smallest difference in the magnetic field shielding

Photochromic derivatives of indigo: historical overview of development, challenges and applications

• Gökhan Kaplan,
• Zeynel Seferoğlu and
• Daria V. Berdnikova

Beilstein J. Org. Chem. 2024, 20, 228–242, doi:10.3762/bjoc.20.23

• substituents in the isatin ring showed pronounced negative photochromism upon irradiation with red light (625−650 nm). Supramolecular complexation with Schreiner’s thiourea organocatalyst (STC) allowed to reach better conversion with the isomeric ratio in PSS increased from 46% to 84%. The backward switching

• ; irradiated with orange light (λirr > 520 nm): dash-dotted line. In all cases irradiation time t = 5 min. Reprinted with permission from ref. [38]. Copyright (1965) American Chemical Society. Photoisomerization of compound 18c upon irradiation with red light and schematic representation of the complexation of

• species. Zwitterionic resonance structures of Z-indigo. Photos of crystalline N,N'-di(Boc)indigo 17a its solutions in 1) DMSO, 2) DMF, 3) N-methyl-2-pyrrolidone. Structural isomers of indigo. Photochromism of indirubin derivatives and supramolecular complexation of the E-isomers with Schreiner’s thiourea

Biphenylene-containing polycyclic conjugated compounds

• Cagatay Dengiz

Beilstein J. Org. Chem. 2023, 19, 1895–1911, doi:10.3762/bjoc.19.141

• successfully obtained in 30% yield. In the final step, the target POA-type structure containing naphthazarin 69 was synthesized by aromatization under acidic conditions. The attempts to conduct complexation experiments using BF3·OEt2 to obtain a stable BF2 complex were unsuccessful, primarily due to solubility

• complexation step to isolate stable BF2 complex of 69, likely attributable to solubility issues encountered with substrate 69, prevented the incorporation of the acene backbone into the structure. Consequently, the anticipated red-shift in the absorption spectrum could not be observed as expected. Boron-doped

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

• obtained by CuAAC in the presence of CuCl(SIMes)(4,7-diclorophenantroline) as catalyst, with very good yields. Next, we set to study the ability of compound 6 to form copper(I) complexes able to act as active-metal templates for [2]rotaxane synthesis. Therefore, complexation studies of 6 with CuCl(SIMes

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

• [46]. The macrotetracycles and macropentacycles, apart from the apparent metal complexation within the porphyrin core, showed cationic guest binding upon adding different ammonium salts, forming 1:1 complexes. Later, in 1985, Camilleri and co-workers reported the synthesis of a capped porphyrin

• slightly enhanced upon complexation. Crowned calixpyrroles In 2008, Sessler and co-workers synthesised an ion-pair receptor incorporating a calix[4]pyrrole framework functionalised with the crown ether units attached through meso-aryl groups (Scheme 1) [101]. The system comprised a crown-6-calix[4]arene

• affinity towards a dipyridinium cation (Figure 8) [41]. Upon complexation, the guest was sandwiched between the porphyrin and crown ether macrocycles. The work showed a 1:1 complex [10-PQ+](PF6)2 formation between the electron-poor bipyridinium guest and hybrid macrocycle 10, indicating a relatively strong

Cyclodextrins permeabilize DPPC liposome membranes: a focus on cholesterol content, cyclodextrin type, and concentration

• Ghenwa Nasr,
• Hélène Greige-Gerges,
• Sophie Fourmentin,
• Abdelhamid Elaissari and
• Nathalie Khreich

Beilstein J. Org. Chem. 2023, 19, 1570–1579, doi:10.3762/bjoc.19.115

• time because it does not fully consider the complexation process between the CDs and the membrane components. Another finding obtained by Nishijo and his co-workers [30] may further clarify this idea. The authors studied the interaction of various CDs with CHOL: heptakis(2,6-di-O-methyl)-β-CD (DOM-β-CD

• with time is additionally accounted for the complexation process occurring between the CDs and the membrane components [30]. Interestingly, a decrease in the permeability was reported with various CDs after t0 (Figure 2 and Figure 3). This result could be in line with the ability of CDs to stabilize

Complexes of resorcin[4]arene with secondary amines: synthesis, solvent influence on “in-out” structure, and theoretical calculations of non-covalent interactions

• Waldemar Iwanek

Beilstein J. Org. Chem. 2023, 19, 1525–1536, doi:10.3762/bjoc.19.109

• ], amino alcohols [10], and amino acids [11] have been studied due to their potential applications in supramolecular chemistry, drug delivery, and molecular recognition. The complexation of R[4]A with amines is based on the formation of hydrogen bonds between the hydroxy groups of the resorcinol units and

• the amine nitrogen of the guest molecule. In addition to hydrogen bonding, other interactions such as π–π stacking and electrostatic interactions also play a role in the complexation process. These interactions can be modulated by changing the pH, solvent, and temperature of the solution. The binding

α-(Aminomethyl)acrylates as acceptors in radical–polar crossover 1,4-additions of dialkylzincs: insights into enolate formation and trapping

• Angel Palillero-Cisneros,
• Paola G. Gordillo-Guerra,
• Fernando García-Alvarez,
• Olivier Jackowski,
• Franck Ferreira,
• Fabrice Chemla,
• Joel L. Terán and
• Alejandro Perez-Luna

Beilstein J. Org. Chem. 2023, 19, 1443–1451, doi:10.3762/bjoc.19.103

• alkylidenemalonates [9][10][11]. These reactions follow a free-radical chain process wherein alkyl radicals (R•) add across the C–C double bond of the 1,4-acceptor, activated by complexation with the dialkylzinc, to deliver an enoxyl radical that undergoes homolytic substitution at zinc (SH2) to produce a zinc

Non-noble metal-catalyzed cross-dehydrogenation coupling (CDC) involving ether α-C(sp³)–H to construct C–C bonds

• Hui Yu and
• Feng Xu

Beilstein J. Org. Chem. 2023, 19, 1259–1288, doi:10.3762/bjoc.19.94

• copper is to activate the 1,3-dicarbonyl compounds through complexation that leads to a highly diastereoselective nucleophilic addition. Scheidt et al. reported an enantioselective Cu-catalyzed intramolecular cross-dehydrogenative coupling approach to substituted tetrahydropyrans with excellent yields

Unravelling a trichloroacetic acid-catalyzed cascade access to benzo[f]chromeno[2,3-h]quinoxalinoporphyrins

• Chandra Sekhar Tekuri,
• Pargat Singh and
• Mahendra Nath

Beilstein J. Org. Chem. 2023, 19, 1216–1224, doi:10.3762/bjoc.19.89

• copper complexes of benzo[f]chromeno[2,3-h]quinoxalinoporphyrins 3–7 were converted to the corresponding free-base porphyrinoids 9–13 through a standard demetallation process using conc. H2SO4 in CHCl3 under cooling conditions (Scheme 1). On complexation with zinc by using Zn(OAc)2 in CHCl3/MeOH, free