Gold extraction at the molecular level using α- and β-cyclodextrins

• Susana Santos Braga

Beilstein J. Org. Chem. 2025, 21, 1116–1125, doi:10.3762/bjoc.21.89

• diffraction of single crystals (Figure 3), showing, for both 1:1 and 2:1 stoichiometries, cyanoaurate anions inside the host cavity and potassium cations interacting with hydroxy groups of adjacent cyclodextrins. The strong host–guest affinity and complex stability in the solution phase has been studied by

• . A common process of extraction of gold from e-waste is through acid leaching (typically with acqua regia), in which gold is dissolved in the form of tetrachloroaurate anions (AuCl4−). Subsequently, gold is precipitated upon conversion to its metallic form (Au0) using an affordable reducing agent

• saturated solution of β-CD and DBC at 0.1% (v/v) and stirred for five minutes to ensure maximal gold precipitation. Conversion of the [AuBr4]− anions trapped in the co-precipitate to gold metal was done by adding a reducing solution of N2H4·H2O. The process further allowed recycling β-CD from the solution

Supramolecular assembly of hypervalent iodine macrocycles and alkali metals

• Krishna Pandey,
• Lucas X. Orton,
• Grayson Venus,
• Waseem A. Hussain,
• Toby Woods,
• Lichang Wang and
• Kyle N. Plunkett

Beilstein J. Org. Chem. 2025, 21, 1095–1103, doi:10.3762/bjoc.21.87

• dynamic assembly and disassembly. Our previous study [18] demonstrates the synthesis of various HIM variants, including a new phenylalanine-based HIM, which show the dynamic behavior of HIM assemblies in solution via addition and removal of anions (Figure 1A). Moreover, due to secondary bonding in the HIM

• systems, these macrocycles display dynamic behavior even in the absence of extra anions, with monomers swapping between macrocycles to participate in dynamic covalent chemistry. As a demonstration of even higher supramolecular assemblies, we also showed π-extended HIMs enable the co-assembly of

• region. Additional information of the electrostatic potential map with color code is provided in the supporting information (Supporting Information File 1, Figure S14). We recently reported that anions of tetrabutylammonium salts such as F−, Cl−, Br−, and CN− disrupt the secondary bonding in the HIMs and

Recent advances in synthetic approaches for bioactive cinnamic acid derivatives

• Betty A. Kustiana,
• Galuh Widiyarti and
• Teni Ernawati

Beilstein J. Org. Chem. 2025, 21, 1031–1086, doi:10.3762/bjoc.21.85

• -workers (2019) employed a non-metal Lewis acid tritylium salt (TrBF4) to catalyze the stereoselective olefination of α-diazocarbonyl compounds 438 to access Z-cinnamate esters 439–442 via 1,2-hydride migration (443) (Scheme 89) [151]. The ion pair of carbocation, BF4− anions, and the trityldiazene group

Recent advances in controllable/divergent synthesis

• Jilei Cao,
• Leiyang Bai and
• Xuefeng Jiang

Beilstein J. Org. Chem. 2025, 21, 890–914, doi:10.3762/bjoc.21.73

• mechanistic experiments and DFT calculations, the authors proposed a possible mechanism for the reaction: first, DPZ is excited by light to form the excited state DPZ*, which then oxidizes bromide ions through single-electron transfer to generate corresponding radical anions. These radical anions undergo

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

• Sciences, Beijing 100049, China 10.3762/bjoc.21.72 Abstract The efficient binding of dicarboxylates represents an important yet challenging issue in supramolecular chemistry. In this study, we designed functional ultracycles as hosts to accommodate large organic dicarboxylate anions. These ultracycles

• ultracycles in hand, we investigated the binding between the [2 + 2] ultracycle B4aH, which contains two electron-deficient cavities, and a series of dicarboxylate anions (C22−–C82− as tetrabutylammonium salts) by 1H NMR titration experiments (Figure 2). Taking C62− as an example, when it was added dropwise

• binding model, with two-step binding constants of K11 = 259 M−1 and K12 = 251 M−1, implying that B4aH can accommodate two C22− anions as a dimer within its cavity [29]. Malonate (C32−) and succinate (C42−) exhibited irregular titration curves (Figure 2c), and no reliable binding constants could be

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

• /bjoc.21.68 Abstract The dual-host strategy offers a straightforward approach to ion separation, yet the nature of cooperative interactions between receptor-complexed cations and anions remains poorly understood. In this study, we utilize 18-crown-6 as a cation receptor and a tripodal hexaurea receptor

• separation [4][5][6][7][8]. Building on the extensive research into anion and cation receptors within the realm of supramolecular chemistry [9][10][11][12], numerous heteroditopic ion-pair receptors have been elaborately developed [13][14][15]. These receptors, consisting of binding sites for both anions and

• and making new receptors, thereby saving considerable time. However, the selectivity of ion separation achieved through the dual-host strategy may not match that of ion-pair receptors, possibly due to less defined interactions between the receptor-complexed anions and cations. Early studies employing

Recent advances in the electrochemical synthesis of organophosphorus compounds

• Babak Kaboudin,
• Milad Behroozi,
• Sepideh Sadighi and
• Fatemeh Asgharzadeh

Beilstein J. Org. Chem. 2025, 21, 770–797, doi:10.3762/bjoc.21.61

• carbonyl group. The halide salts did not lead to product formation, indicating that chloride and bromide anions cannot generate the corresponding radicals to accelerate the conversion of diphenylphosphine. The reaction yield decreased when the methyl group was placed in ortho-position. Moreover, the

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

Organocatalytic kinetic resolution of 1,5-dicarbonyl compounds through a retro-Michael reaction

• James Guevara-Pulido,
• Fernando González-Pérez,
• José M. Andrés and
• Rafael Pedrosa

Beilstein J. Org. Chem. 2025, 21, 473–482, doi:10.3762/bjoc.21.34

• yields [27]. These reactions have been utilized in the enantioselective synthesis of aryl sulfoxides through the arylation of sulfonate anions in the presence of palladium catalysts [28][29]. They have also been used in the synthesis of the neuraminidase inhibitor (−)-oseltamivir [30] and the

Electrochemical synthesis of cyclic biaryl λ³-bromanes from 2,2’-dibromobiphenyls

• Andrejs Savkins and
• Igors Sokolovs

Beilstein J. Org. Chem. 2025, 21, 451–457, doi:10.3762/bjoc.21.32

• change of the anode material from GC to RVC or BDD (entries 8 and 9, Table 1), variation of electrolyte amount (entries 10 and 11) or altering of counter anions in the supporting electrolyte (entries 12 and 13; for complete optimization results, see Supporting Information File 1, Table S1). With the

The effect of neighbouring group participation and possible long range remote group participation in O-glycosylation

• Rituparna Das and
• Balaram Mukhopadhyay

Beilstein J. Org. Chem. 2025, 21, 369–406, doi:10.3762/bjoc.21.27

• -butyldimethylsilyloxy)-2,2-dimethylbutanoyl protecting group 33 [102] possessing the steric advantage of the pivaloyl group with the added advantage of it being cleaved with the help of fluoride anions implementing the affinity of the fluoride ion towards the Si atom [103]. Considering the versatility of the pivaloyl

Synthesis, structure, ionochromic and cytotoxic properties of new 2-(indolin-2-yl)-1,3-tropolones

• Yurii A. Sayapin,
• Eugeny A. Gusakov,
• Inna O. Tupaeva,
• Alexander D. Dubonosov,
• Igor V. Dorogan,
• Valery V. Tkachev,
• Anna S. Goncharova,
• Gennady V. Shilov,
• Natalia S. Kuznetsova,
• Svetlana Y. Filippova,
• Tatyana A. Krasnikova,
• Yanis A. Boumber,
• Alexey Y. Maksimov,
• Sergey M. Aldoshin and
• Vladimir I. Minkin

Beilstein J. Org. Chem. 2025, 21, 358–368, doi:10.3762/bjoc.21.26

• the 7,8 (OH) form and is caused by the excited-state intramolecular proton transfer (ESIPT) process due to intramolecular O→N proton migration in the singlet excited state [26][27]. The ionochromic sensitivity of compounds 7a,b and 8a,b to anions was investigated in acetonitrile upon addition of tetra

• -n-butylammonium salts (TBAX: F, Cl, Br, I, CN). Exclusively cyanide and fluoride anions lead to a naked-eye effect due to a change of the solution’s colour from yellow-orange to pale yellow (Figure 5). At the same time, a new fluorescence band appears at 420–440 nm. The Stokes shifts of fluorescence

• corresponding solution (1 mL) and the tetra-n-butylammonium salt (1 mL) solution were mixed directly in the cell and thoroughly stirred. Hence, the working concentrations of compounds 7 or 8 and anions was 2.5 × 10−5 mol L−1 and 5.0 × 10−5 mol L−1, respectively. All spectral experiments were performed at room

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

• counterions, such as the bromide and fluoride anions [50], on HB interactions, all ionic compounds were synthesized with tetrafluoroborate, a classical weakly coordinating anion. Results and Discussion We first assessed the hydrogen bond acidity, A, of these CF2H-containing compounds using an established

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

• these conditions the reaction between aryl thiosulfonates with arynes to give sulfones is competitive. Cu(OTf)2 is essential to remove the sulfinate anions in the reaction medium, avoiding side reactions arising from their attack to the electrophilic arynes. The so-obtained products are susceptible of

Reactivity of hypervalent iodine(III) reagents bearing a benzylamine with sulfenate salts

• Beatriz Dedeiras,
• Catarina S. Caldeira,
• José C. Cunha,
• Clara S. B. Gomes and
• M. Manuel B. Marques

Beilstein J. Org. Chem. 2024, 20, 3281–3289, doi:10.3762/bjoc.20.272

• reactivity with in situ-generated sulfenate anions, from β-sulfinyl esters, to achieve S–N bond formation. The importance of establishing this S–N bond results from the widespread presence of sulfonyl-containing bioactive compounds, such as the sulfonamide group which can be found in many pharmaceuticals

• 5aa (Table 1, entry 2) but with prior degassed solvent (DMF), to prevent potential oxidation of the sulfenate to sulfinate anions. Indeed, the oxidation of the unstable sulfenate intermediates has been previously reported by Waser when using EBX – an HIR applied in the transfer of alkynes to sulfenate

Surprising acidity for the methylene of 1,3-indenocorannulenes?

• Shi Liu,
• Märt Lõkov,
• Sofja Tshepelevitsh,
• Ivo Leito,
• Kim K. Baldridge and
• Jay S. Siegel

Beilstein J. Org. Chem. 2024, 20, 3144–3150, doi:10.3762/bjoc.20.260

• compounds tend to deprotonate to form highly stable anions. The air stability of TBF conforms to that model. In contrast, although the dianion of BFC can be generated with tert-butoxide under inert atmosphere, in the presence of water it quenches and exposed to oxygen it oxidizes to form the diketone

• pentabenzocorannulene would produce air-stable radical and ionic PAHs, and that coupling such fragments would lead to stable redox-active carbon sheets. Conclusion In conclusion, the “surprise” in the surprising pKa for BIC and FIC was in our expectation of the deprotonated forms as poorly delocalized fluorenyl anions

Advances in the use of metal-free tetrapyrrolic macrocycles as catalysts

• Mandeep K. Chahal

Beilstein J. Org. Chem. 2024, 20, 3085–3112, doi:10.3762/bjoc.20.257

• metal-free porphyrins. 1.1 Calix[4]pyrrole macrocycles as organocatalysts Calix[4]pyrroles act as versatile ligands in supramolecular chemistry and have been widely studied as binding hosts for various guests such as anions, ion pairs, or neutral compounds [4][30][31], ligands for p-block elements, as

Tunable full-color dual-state (solution and solid) emission of push–pull molecules containing the 1-pyrindane moiety

• Anastasia I. Ershova,
• Sergey V. Fedoseev,
• Konstantin V. Lipin,
• Mikhail Yu. Ievlev,
• Oleg E. Nasakin and
• Oleg V. Ershov

Beilstein J. Org. Chem. 2024, 20, 3016–3025, doi:10.3762/bjoc.20.251

• ], positron emission tomography (PET) imaging [24], fluorescent probes and labels [25][26][27] detecting H2S in foodstuff, water, and living cells [28], Fe3+ ions [29], Hg2+ ions [30], and cyanide anions [31], for acid–base vapor sensing [32], and as candidate material for photonics devices, optical switches

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

• ; metallocontainer; oxalate; Introduction Dicarboxylic acids and their corresponding anions are essential intermediates in the biosynthesis of proteins and important biological metabolites [1][2]. As a result, the development of receptors for this class of compounds is of high interest [3][4][5]. Oxalate, the

• metallocontainers which are formed by metal-driven self-assembly have become especially popular to bind various kinds of anions since such systems offer easy to tune confinements. Usually, the utilized complexes are net positive which makes them ideal hosts for anions [56][57][58][59][60][61][62][63]. However, the

• positively charged or charge-neutral, is their metal-driven self-assembly. Unfortunately, this can also be their Achilles' heel, as the underlying coordination bonds are fragile compared to covalent bonds. For example, metallocages can easily break apart by the addition of competitive anions which are highly

Recent advances in transition-metal-free arylation reactions involving hypervalent iodine salts

• Ritu Mamgain,
• Kokila Sakthivel and
• Fateh V. Singh

Beilstein J. Org. Chem. 2024, 20, 2891–2920, doi:10.3762/bjoc.20.243

• nature of X− [45][46]. Anions like tetrafluoroborate, hexafluorophosphate, and trifluoromethanesulfate are commonly used in DAIS due to their good solubility and weak nucleophilicity. If the two aryl groups (Ar1 and Ar2) in DAIS are different, they are termed unsymmetric diaryliodonium salts 3. The

• diaryliodonium salts regardless of their differing counter-anions. A range of 2-naphthol substrates, including those bearing alkyl and aryl groups, halogens, trimethylsilyl, and protected hydroxy at positions 6 and 7, exhibited good tolerance. However, the reaction with 1-naphthol did not yield positive results

• diaryliodonium salts. Recent advancements in this field have focused on the development of practically simple and scalable methods for the arylation of oxygen using diaryliodonium salts. By modifying the counter anions attached to the iodonium ion, the stability and reactivity of new symmetrical and

Investigation of a bimetallic terbium(III)/copper(II) chemosensor for the detection of aqueous hydrogen sulfide

• Parvathy Mini,
• Michael R. Grace,
• Genevieve H. Dennison and
• Kellie L. Tuck

Beilstein J. Org. Chem. 2024, 20, 2818–2826, doi:10.3762/bjoc.20.237

• removal of Na2S followed by the precipitation and re-addition of Cu2+ ions (Figure 5). Comprehensive selectivity studies were conducted with various anions/sulfur compounds (SO42−, SO32−, S2O52−, S2O42−, S2O32−, ClO−, OAc−, NO3−, I−, HCO3−, CO32−, Cl−, lipoic acid, and glutathione, as depicted in Figure 6

• are highly selective to HS−(aq) ions and are thus suitable for environmental or biological studies where interfering anions may be present. Gaseous H2S studies of [Tb.1·3Cu]3+ We aimed to further investigate the luminescence response of Tb3+ analogues upon exposure to hydrogen sulfide gas, building

• ), was incrementally spiked with a standard solution of 1 mM Na2S(aq). The time-gated luminescence emission spectrum (λex = 250 nm) of the solution was recorded after each addition. Competition assay with anions and cations: The time-gated luminescence emission change of a solution of [Tb.1·3Cu]3+ (5 μM

Mechanochemical difluoromethylations of ketones

• Jinbo Ke,
• Pit van Bonn and
• Carsten Bolm

Beilstein J. Org. Chem. 2024, 20, 2799–2805, doi:10.3762/bjoc.20.235

• reactions of difluorocarbene with cyclic and acyclic 1,3-diones (Scheme 1A) [41][42][43][44][45]. Typically, they were conducted with a base to form the corresponding enolate anions which then reacted with difluorocarbene to yield difluoromethyl enol ethers. Those products are of interest because they

C–C Coupling in sterically demanding porphyrin environments

• Liam Cribbin,
• Brendan Twamley,
• Nicolae Buga,
• John E. O’ Brien,
• Raphael Bühler,
• Roland A. Fischer and
• Mathias O. Senge

Beilstein J. Org. Chem. 2024, 20, 2784–2798, doi:10.3762/bjoc.20.234

• alternatively by core protonation, whereby all four-core nitrogen atoms are protonated to produce the diacid [12][13]; these diacids can tilt the pyrrole rings 20–40° [14] from the mean-porphyrin plane. Norvaiša et al. showed that a saddle-shaped porphyrin as a dodecasubstituted diacid can bind anions via two

• independent faces and trap anions such as pyrophosphate [15]. Saddle-shaped porphyrins have also been exploited by researchers for the use in organocatalysis as bifunctional system [16][17]. Dodecasubstitution of porphyrin, as seen in Figure 1, often results in saddle-shaped distortion; however, ruffled [18

Efficient modification of peroxydisulfate oxidation reactions of nitrogen-containing heterocycles 6-methyluracil and pyridine

• Alfiya R. Gimadieva,
• Yuliya Z. Khazimullina,
• Aigiza A. Gilimkhanova and
• Akhat G. Mustafin

Beilstein J. Org. Chem. 2024, 20, 2599–2607, doi:10.3762/bjoc.20.219

• generate sulfate anion radicals (SO4•−) [42] during their interaction with sulfate anions. This reaction occurs at a significant rate (k = 3.1∙108 min−1) [43] and leads to the recombination of peroxydisulfate in the reaction mixture. It has been demonstrated that the efficiency of peroxydisulfate

Anion-dependent ion-pairing assemblies of triazatriangulenium cation that interferes with stacking structures

• Yohei Haketa,
• Takuma Matsuda and
• Hiromitsu Maeda

Beilstein J. Org. Chem. 2024, 20, 2567–2576, doi:10.3762/bjoc.20.215

• ] formed a charge-by-charge assembled structure, with alternate stacking of TATA+ and PCCp− through iπ–iπ interactions in the crystal state [20][21]. Charge-by-charge stacking assemblies of 1a+ and porphyrin-based π-electronic anions showed the crystal-state PET between proximally located anions and

• cations [21]. Moreover, ion-pairing assemblies of 1a+ and the π-electronic receptor–anion complexes as pseudo-π-electronic anions exhibited electric conductive properties [22][23][24][25]. The structures and electronic states of ions directly affect the arrangement of constituent ions in the assemblies

• PF6− anions located above the TATA+ plane (Figure 3b,c and Figure 5b,c). Three of the fluorine atoms of BF4− and PF6− were pointed toward the TATA+ plane. The offset angles for Cl−, BF4−, and PF6− to the TATA+ central carbon were 87.7°, 78.1°, and 84.3°, respectively. The distances between fluorine