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

• -precipitation yields from aqueous solutions of α-CD (20 mM) and MAuBr4 (10 mM) (M = Na/K/Rb/Cs) measured at 20 °C by UV–vis spectrophotometry. Right) Structures of the adducts present in co-precipitates with different alkali metals. Reproduced from Z. Liu et al. [40], “Cation-Dependent Gold Recovery with α

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

• at Urbana-Champaign, Urbana, IL, 61801, United States 10.3762/bjoc.21.87 Abstract This study explores the solution- and solid-state assembly of phenylalanine-based hypervalent iodine macrocycles (HIMs) with lithium and sodium cations. The metal cation binding of HIMs was evaluated by addition of

• pattern of assembly between HIM and metal cation in 2:1 ratio. While association with sodium leads to a polymer-like network, the lithium crystal structure was limited to dimeric assemblies of HIM. In the lithium-coordinating complex, the oxygen–lithium–oxygen bond angle is approximately 98.83

• Buckminster fullerene into long range assembled structures (Figure 1B) [20]. In this contribution, we explored the cation binding abilities of HIMs with first group alkali metals such as lithium and sodium. The phenylalanine-based HIM 1 used in this study was re-synthesized following the previously reported

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

• O atom of the carboxylate group. For instance, Coote and co-workers (2019) reported electrochemical methylation of cinnamic acid 7 using the TEMPO-Me reagent via reactive radical cation 59 to give the corresponding methyl ester 44 in moderate yield (Scheme 21A) [53]. Wang and co-workers (2019

• cinnamate (44) via an electrochemical method using TBAF as the supporting electrolyte (Scheme 56) [99]. Under these conditions, the aldehyde was oxidized to give an oxonium cation intermediate 176. Moreover, Babu and co-workers (2024) oxidized an imine, cinnamalaldehyde N-tosylhydrazone (177), by using TBHP

Recent total synthesis of natural products leveraging a strategy of enamide cyclization

• Chun-Yu Mi,
• Jia-Yuan Zhai and
• Xiao-Ming Zhang

Beilstein J. Org. Chem. 2025, 21, 999–1009, doi:10.3762/bjoc.21.81

• quaternary center in a single step. As depicted in Scheme 1, key enamide 1 was prepared from (R)-pulegone in 6 steps. In the presence of the weak acid H3PO4, protonation of 1 generates a stabilized iminium ion 2, which then undergoes a 6-exo-trig cyclization to deliver 4 after hydration of cation 3. Notably

Harnessing tethered nitreniums for diastereoselective amino-sulfonoxylation of alkenes

• Shyam Sathyamoorthi,
• Appasaheb K. Nirpal,
• Dnyaneshwar A. Gorve and
• Steven P. Kelley

Beilstein J. Org. Chem. 2025, 21, 947–954, doi:10.3762/bjoc.21.78

• , which attacks the pendant olefin to form an aziridinium cation (Scheme 2). A sulfonate counter-anion then opens this aziridinium ring in an exo-selective, SN2 reaction. We were successful in scaling the reaction from 0.3 mmol to 11.5 mmol (38-fold increase) without any erosion in yield or selectivity

Study of tribenzo[b,d,f]azepine as donor in D–A photocatalysts

• Katy Medrano-Uribe,
• Jorge Humbrías-Martín and
• Luca Dell’Amico

Beilstein J. Org. Chem. 2025, 21, 935–944, doi:10.3762/bjoc.21.76

• facilitated by reduced photocatalyst (PC) and the interaction of 15 with the radical cation of DIPEA. The best result, again, was attributed to molecule 5a with 60% isolated yield (Table 5, entry 1). In contrast, molecule 5b showed the worst performance with 41% NMR yield (Table 5, entry 2). For compounds 5c

Cu–Bpin-mediated dimerization of 4,4-dichloro-2-butenoic acid derivatives enables the synthesis of densely functionalized cyclopropanes

• Patricia Gómez-Roibás,
• Andrea Chaves-Pouso and
• Martín Fañanás-Mastral

Beilstein J. Org. Chem. 2025, 21, 877–883, doi:10.3762/bjoc.21.71

• the base metal cation. Gratifyingly, we observed that the use of LiOt-Bu led to the formation of product 2 as a single diastereomer (Table 1, entry 5). A slightly lower diastereoselectivity was observed when KOt-Bu was used, which also gave rise to 2 in diminished yield (Table 1, entry 6). The nature

• addition to a second molecule of 1. Given the negative results observed for other crotonate derivatives (Scheme 3c), coordination between the Li cation and the two chlorine atoms via proposed transition state D may be crucial not only for diastereoselective control but also for the viability of this step

• second molecule of the 4,4-dichloro-2-butenoic acid derivative. We have observed that the use of lithium as base metal cation is key to achieve excellent levels of diastereoselectivity. Our study also highlights, how the dimerization products can be selectively converted into different densely

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

• dual-host systems for selective ion separation. Keywords: anion binding; cesium extraction; dual-host strategy; ion-pair interaction; solid–liquid extraction; Introduction Ion-pair interaction, defined as the electrostatic attraction between a positively charged cation and a negatively charged anion

• 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

4-(1-Methylamino)ethylidene-1,5-disubstituted pyrrolidine-2,3-diones: synthesis, anti-inflammatory effect and in silico approaches

• Nguyen Tran Nguyen,
• Vo Viet Dai,
• Luc Van Meervelt,
• Do Thi Thao and
• Nguyen Minh Thong

Beilstein J. Org. Chem. 2025, 21, 817–829, doi:10.3762/bjoc.21.65

• organic cation transporter 2 (OCT2) was examined, with OCT2 playing a pivotal role in the renal elimination of both xenobiotics and endogenous compounds. The predicted results suggest that none of the studied compounds act as OCT2 substrates. Toxicity was assessed using the Ames test, a widely accepted

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

• (O)(OR)2 is derived from the compound P(OR)3, not from HP(O)(OR)2. Although the exact role of HP(O)(OR)2 remains unclear, it has been established that its presence is essential for the C–H phosphorylation. In this case, a radical cation intermediate was suggested for this conversion. Heteroaromatic

• . Some other heteroarenes were also tested, but only quinoxaline was compatible with this system under the standard conditions. A radical pathway was proposed in this reaction. At first, a thiazole radical cation was formed via anodic oxidation, followed by a reaction with phosphine oxides to give a

• reaction proceeded via anodic indole oxidation, followed by a reaction with trialkyl phosphite to give the corresponding indole phosphonate (Scheme 11). Cyclic voltammetry experiments confirmed that free indole can oxidize at the anode and generate a radical-cation intermediate. Also, no product was

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

• internal rotation in 11 via TS8 and reaction with TMSCN to give adduct 13 (see Figure 3). Distances and bond lengths are given in pm. Catalyst 7 is replaced in TS 11-12 by concerted electrophilic intramolecular substitution with formal trimethylsilyl cation as electrophile. Please note the surprisingly

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

• acetylcholine-type unit (Me3NCH2CH2O(C=O)R) range from 3.5 Å to 5 Å with a maximum probability of 4.4 Å [74]. Figure 6 shows Me3N+···O=C contacts that are less than 4.40 Å. The large number of contacts that are significantly shorter than 4.40 Å establishes that Me3N+···O=C cation–dipole interactions play an

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

• -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

• -diborylalkanes 47 using an H8-BINOL-derived phosphoramidite ligand L5, achieving exceptional enantiocontrol (Scheme 16) [59]. Their studies revealed the critical role of both the alkali metal cation and boronic ester moiety. While LiOt-Bu provided excellent enantioselectivity (er = 95:5), NaOt-Bu and KOt-Bu

Entry to 2-aminoprolines via electrochemical decarboxylative amidation of N‑acetylamino malonic acid monoesters

• Olesja Koleda,
• Janis Sadauskis,
• Darja Antonenko,
• Edvards Janis Treijs,
• Raivis Davis Steberis and
• Edgars Suna

Beilstein J. Org. Chem. 2025, 21, 630–638, doi:10.3762/bjoc.21.50

• initial deprotonation of carboxylic acid 9a by cathodically generated hydroxide is followed by anodic oxidation/decarboxylation of the formed carboxylate 9a-I to generate stabilized cation 9a-II. The latter undergoes intramolecular cyclization with the tethered N-nucleophile into cyclic aminal 6a. In a

• competing reaction, the cation 9a-II reacts with water to form acyclic hemiaminal 10a. With the optimized conditions in hand (Table 1, entries 8 and 10) the scope of the developed decarboxylative amidation was briefly explored (Scheme 3). N-Acetyl, N-Cbz, and N-Bz protecting groups are compatible with the

• provides access to previously unreported 2-aminoproline derivatives. The decarboxylative amidation proceeds under constant current conditions in an undivided cell in aqueous acetonitrile and involves initial anodic decarboxylation followed by an intramolecular reaction of the formed stabilized cation with

Asymmetric synthesis of β-amino cyanoesters with contiguous tetrasubstituted carbon centers by halogen-bonding catalysis with chiral halonium salt

• Yasushi Yoshida,
• Maho Aono,
• Takashi Mino and
• Masami Sakamoto

Beilstein J. Org. Chem. 2025, 21, 547–555, doi:10.3762/bjoc.21.43

• present reaction, and products 17l and 17m were isolated in high yields with moderate to high stereoselectivities. The plausible reaction mechanism is shown in Figure 3. First, the removal of the acidic proton of the pre-nucleophile by potassium carbonate to form intermediate I, which undergoes cation

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

• moiety in the amino acid. This hypothesis is also supported by the significant quenching of the fluorescence of the naphthalene unit in 1 upon addition of increasing amounts of H-Trp-OH to the solution. Additionally, cation–π interactions between the ammonium cation of the guest and the naphthalene of

• fluorescence measurements where a strong quenching of the naphthalene fluorescence upon addition of each of the Trp-containing tripeptides 2–7 was observed. For peptides 2 and 3 interactions of the receptor with the N-terminal ammonium cation are likely also involved in the binding process (Figure 5). This is

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

• starts with a single-electron oxidation of 4a on the electrode surface to form cation radical A, in which Br(II) is chelation-stabilized by the carboxyl group [21] and the neighbouring Br substituent [24]. Intermediate A rapidly undergoes irreversible chemical reaction by HFIP coordination to transient

Red light excitation: illuminating photocatalysis in a new spectrum

• Lucas Fortier,
• Corentin Lefebvre and
• Norbert Hoffmann

Beilstein J. Org. Chem. 2025, 21, 296–326, doi:10.3762/bjoc.21.22

• the radical cation iPr2NEt•+ (iPr2NEt/iPr2NEt•+ = +0.72 V vs SCE) and the reduction of O2 by the reduced photocatalyst, forming the superoxide radical anion O2•− (O2/O2•− = −0.57 V vs SCE). This latter can then react with arylboronic acids 59 to give, after hydrolysis, phenol derivatives 60. Other

• involving π–π-stacking [75]. The resulting radical anion releases NO also yielding the anion 63. Electron transfer to the radical cation of the photocatalyst regenerates it. In this step, the neutral radical 64 is also formed. Hydrogen abstraction (hydrogen atom transfer, HAT) yields compound 65. NO and the

Oxidation of [3]naphthylenes to cations and dications converts local paratropicity into global diatropicity

• Abel Cárdenas,
• Zexin Jin,
• Yong Ni,
• Jishan Wu,
• Yan Xia,
• Francisco Javier Ramírez and
• Juan Casado

Beilstein J. Org. Chem. 2025, 21, 277–285, doi:10.3762/bjoc.21.20

• defects are extended over the whole molecule (vide infra). Thus, an extended π-electron delocalization effect in 1•+ stabilizes the cation and shifts anodically the second oxidation. On the contrary, the charge in 2•+ is expected to be largely confined in the central NAP, and the second oxidation would

• oxidized species of compounds 1 and 2 are shown in Figure 3. Initial electrochemical oxidation of 1 resulted in the progressive replacement of its absorption bands by three new features, which were assigned to the 1•+ radical cation, namely at 352/369 nm, a multiplet in the 500–600 nm interval, and a broad

• peak centered at 1173 nm. Further oxidation resulted in a quite silent vis–NIR spectrum characterized by one main peak at 312 nm, which was assigned to the 12+ dication. The spectrum of the first oxidized species of 2, the radical cation 2•+, shows a band at 363 nm, a shoulder at 439 nm, and a broad

Streamlined modular synthesis of saframycin substructure via copper-catalyzed three-component assembly and gold-promoted 6-endo cyclization

• Asahi Kanno,
• Ryo Tanifuji,
• Satoshi Yoshida,
• Sota Sato,
• Saori Maki-Yonekura,
• Kiyofumi Takaba,
• Jungmin Kang,
• Kensuke Tono,
• Koji Yonekura and
• Hiroki Oguri

Beilstein J. Org. Chem. 2025, 21, 226–233, doi:10.3762/bjoc.21.14

• antitumor activity, triggered by DNA alkylation [6][7][8]. The aminonitrile/hemiaminal at C21 generates an iminium cation while releasing a cyanide or a hydroxy group under physiological conditions. This iminium cation facilitates nucleophilic attack by guanine residues in the minor groove of the GC-rich

• reaction involves an in situ generation of the iminium cation A followed by isomerization to the thermodynamically more stable iminium cation B. Subsequent nucleophilic attack of a copper acetylide enabled regioselective C–C bond formation at the C11 position. After removal of the cyclic acetal, the

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

• polymers (Scheme 1). The terpyridyl group and the pyridinium cation in the AB-type monomer G2 each function as a “sticker” to enable supramolecular polymerization in the presence of the macrocyclic component and zinc ions. The driving force for the recognition involves multiple cooperative interactions

• dominant peak at m/z = 2444.3405, corresponding to the cation [H12 + G12 − 2PF6−]2+, indicating the presence of a host–guest complex in a 2:2 stoichiometry in the gas state (Figure 1). Job plot experiments provided a 1:1 stoichiometry (Figure S9, Supporting Information File 3), showing consistency with the

Recent advances in electrochemical copper catalysis for modern organic synthesis

• Yemin Kim and
• Won Jun Jang

Beilstein J. Org. Chem. 2025, 21, 155–178, doi:10.3762/bjoc.21.9

• cation 30. The [Mes-Acr-Ph]• is regenerated to the ground-state acridinium [Mes-Acr-Ph]+ through a single oxidation step on the anode, and the heteroarene radical cation 30 then reacts with the arylalkene 27 to form a benzylic radical intermediate 31. The benzylic radical intermediate 31 is subsequently

• Figure 11. Initially, the Cu(II) catalyst 50 coordinates with substrate 47 and amine electrophile 48 to generate Cu(II) intermediate 51, which is then oxidized by the iodine radical to form Cu(III) complex 52. Cu(III) complex 52 undergoes electron transfer to produce radical cation intermediate 53

• . Subsequent intramolecular amine transfer to the radical cation intermediate 53, followed by ligand exchange, yields amination product 49 and Cu(I) species 55. Cu(II) catalyst 50 is regenerated by anodic oxidation, thereby completing the catalytic cycle. In 2019, Nicholls et al. reported a Cu-catalyzed

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

• of promoting the three-component cascade cyclization of 2-formylbenzonitriles, alkyl aryl ketones, and diaryliodonium salts to afford 2-arylisoindolinones 32 (Scheme 24) [41]. It is conceivable that the reaction starts with the formation of an N-arylnitrilium cation XXXI that, after hydrolysis

Controlled oligomerization of [1.1.1]propellane through radical polarity matching: selective synthesis of SF₅- and CF₃SF₄-containing [2]staffanes

• Jón Atiba Buldt,
• Wang-Yeuk Kong,
• Yannick Kraemer,
• Masiel M. Belsuzarri,
• Ansh Hiten Patel,
• James C. Fettinger,
• Dean J. Tantillo and
• Cody Ross Pitts

Beilstein J. Org. Chem. 2024, 20, 3134–3143, doi:10.3762/bjoc.20.259

• , e.g., a radical or cation) on the transannular carbon atom of a bicyclopentyl moiety can interact through space [35][63][64]. The consequence is ostensibly that more "nucleophilic" INT2 and INT5 are better matched for Cl atom abstraction from the "electrophilic" reagent (SF5Cl or CF3SF4Cl). To test

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

• or transform into a long-lived radical cation by substrate reduction, which are the fundamentals of photoredox catalysis (Figure 13a). Monomeric porphyrins and supramolecular porous frameworks composed of porphyrin building blocks, such as metal-organic frameworks (MOF) and covalent organic

• and a photosensitizer, facilitating photoinduced electron transfer (PET) to form the active cation radical B, and intersystem crossing (ISC) for energy transfer to generate the triplet carbene C. Radical B then reacted with biradical C, producing the new radical D, which accepted an electron from the

• porphyrin radical anion. Ultimately, protonation of intermediate E led to the final product. Formation of intermediates, such as enamine A and cation radical B, was confirmed using techniques like ESIMS, 1H NMR, and EPR, Stern–Volmer quenching experiments, respectively. All these mechanistic studies