pH-Controlled isomerization kinetics of ortho-disubstituted benzamidines: E/Z isomerism and axial chirality

• Ryota Kimura,
• Satoshi Ichikawa and
• Akira Katsuyama

Beilstein J. Org. Chem. 2025, 21, 1568–1576, doi:10.3762/bjoc.21.120

• best of our knowledge, although the structural analysis of the E/Z isomerism of amidine [24][25] and the effect of the protonation of an amidine moiety on the rotational barrier of the C–N bond [26] have been studied, the separation of amidine E/Z isomers has not been reported yet. To verify our

• separation of the two peaks, HPLC analysis of each separated component showed single peaks, suggesting that the E and Z isomers of amidine 2 trifluoroacetate salt could be separated by standard RP-HPLC. The configuration of the amidine moiety of each component was characterized by NOE experiments (for

• protonated form calculated by the DFT method. Comparison of VT-NMR spectra of a) amidine 1 and b) its trifluoroacetate salt 1-H+ in DMSO-d6 (400 MHz). Separation and isolation of amidine E/Z isomers by RP-HPLC. The mobile phase contained CF3CO2H to protonate the amidine moiety. Kinetic analysis of the

Ambident reactivity of enolizable 5-mercapto-1H-tetrazoles in trapping reactions with in situ-generated thiocarbonyl S-methanides derived from sterically crowded cycloaliphatic thioketones

• Grzegorz Mlostoń,
• Małgorzata Celeda,
• Marcin Palusiak,
• Heinz Heimgartner,
• Marta Denel-Bobrowska and
• Agnieszka B. Olejniczak

Beilstein J. Org. Chem. 2025, 21, 1508–1519, doi:10.3762/bjoc.21.113

• selectivity, and in all cases formation of insertion products of both types, i. e., thioaminals 9 and dithioacetales 10, was observed (see Table 1). Chromatographic separation enabled the isolation of pure compounds, and the more stable dithioacetals 10 formed the more polar fraction. The less polar fraction

• contained thioaminals 9, which underwent a slow isomerization in CDCl3 solution. Notably, in the case of products 9k and 10k, bearing a Ph group at N(1), after a successful chromatographic separation, the less stable 9k underwent isomerization in CDCl3 solution (at rt) and no registration of NMR spectra of

• in the series of products derived from 1c is slower (and reversible?), and therefore, corresponding products of both N- and S-insertion are side by side observed as components of the crude reaction mixtures and their ratio was always ca. 55:45. In the latter case, chromatographic separation of the

N-Salicyl-amino acid derivatives with antiparasitic activity from Pseudomonas sp. UIAU-6B

• Joy E. Rajakulendran,
• Emmanuel Tope Oluwabusola,
• Michela Cerone,
• Terry K. Smith,
• Olusoji O. Adebisi,
• Adefolalu Adedotun,
• Gagan Preet,
• Sylvia Soldatou,
• Hai Deng,
• Rainer Ebel and
• Marcel Jaspars

Beilstein J. Org. Chem. 2025, 21, 1388–1396, doi:10.3762/bjoc.21.103

• funnel for 5 min to allow for proper separation of the constituent mixture between the aqueous and organic phases. Further partitioning of the aqueous phase with sec-butanol (300 mL × 3) yielded FB fraction (2.3 g) and FW fraction (1.4 g), respectively. The dichloromethane (FD) fraction (3.5 g) was

Oxetanes: formation, reactivity and total syntheses of natural products

• Peter Gabko,
• Martin Kalník and
• Maroš Bella

Beilstein J. Org. Chem. 2025, 21, 1324–1373, doi:10.3762/bjoc.21.101

Recent advances and future challenges in the bottom-up synthesis of azulene-embedded nanographenes

• Bartłomiej Pigulski

Beilstein J. Org. Chem. 2025, 21, 1272–1305, doi:10.3762/bjoc.21.99

• ) can exhibit remarkably red-shifted absorption, even when incorporated into relatively small π-conjugated frameworks. Through careful molecular design – retaining the azulene-like electronic structure and promoting spatial separation of the HOMO and LUMO orbitals – it is possible to achieve

Synthetic approach to borrelidin fragments: focus on key intermediates

• Yudhi Dwi Kurniawan,
• Zetryana Puteri Tachrim,
• Teni Ernawati,
• Faris Hermawan,
• Ima Nurasiyah and
• Muhammad Alfin Sulmantara

Beilstein J. Org. Chem. 2025, 21, 1135–1160, doi:10.3762/bjoc.21.91

• impact the outcome. Subsequently, separation of 84 from 85 was explored using various lipases and an esterase. However, preliminary experiments with these enzymes did not yield satisfactory results. The focus then shifted to route B, utilizing methyl 2,4,6-trimethyloctanoate 88 as the starting material

Investigations of amination reactions on an antimalarial 1,2,4-triazolo[4,3-a]pyrazine scaffold

• Henry S. T. Smith,
• Ben Giuliani,
• Kanchana Wijesekera,
• Kah Yean Lum,
• Sandra Duffy,
• Aaron Lock,
• Jonathan M. White,
• Vicky M. Avery and
• Rohan A. Davis

Beilstein J. Org. Chem. 2025, 21, 1126–1134, doi:10.3762/bjoc.21.90

• described in Supporting Information File 1. Pure fractions (≥95%) obtained from reversed-phase HPLC separation were then combined to obtain the desired product, 3-(4-chlorophenyl)-N-phenethyl-[1,2,4]triazolo[4,3-a]pyrazin-8-amine (2) as yellow needles (115 mg, 82%). General method for the synthesis of the

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

• can yield 150 grams or more of gold, according to a study conducted in Japan in 2008 by recycling companies [50]. It is important, however, that the gold extraction method for e-waste sources is affordable in order to hold up the interest in the recovery, separation, and recycling of these materials

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

• devices or therapeutics [1], drug delivery [2], supramolecular sensing [3], purification [4], and separation [5][6]. The interactions in supramolecular assemblies are driven by well-known hydrogen-bonding, hydrophobic interactions, electrostatic interactions and π–π stacking [7][8]. The supramolecular

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

On the photoluminescence in triarylmethyl-centered mono-, di-, and multiradicals

• Daniel Straub,
• Markus Gross,
• Mona E. Arnold,
• Julia Zolg and
• Alexander J. C. Kuehne

Beilstein J. Org. Chem. 2025, 21, 964–998, doi:10.3762/bjoc.21.80

• functionalized Cz-BTM than in pristine Cz-BTM, with a charge separation distance in the excited state of 0.68 nm versus 0.21 nm, respectively. Quantum chemical investigations have also been employed to understand the strong emission observed experimentally in TTM-Cz. One explanation is based on intensity

• emission wavelength points towards a CT excited state. Apparently upon excitation, symmetry breaking charge separation [94] occurs leading to a (zwitterionic) CT excited state with a diarylmethylene unit acting as a donor and a trityl unit acting as an acceptor [92]. This symmetry breaking charge

• separation seems to be supported in solvents of higher polarity. By contrast, when the polarity of the solvent is increased beyond that of toluene, the ϕ drops to about 10% in THF (λem = 785 nm), which is typical for CT excited states that are stabilized by polar solvents (see Figure 14a) [92]. Similar

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

• behavior is supported by the DFT studies, which suggested a better spatial separation between the HOMO and LUMO. As expected, the HOMO–LUMO energy gap followed a trend that is dependent on the electron-donating capacity of the nitrogen heterocycles and amine present in compounds 5e (2.9 eV), 5d (3.5 eV

A convergent synthetic approach to the tetracyclic core framework of khayanolide-type limonoids

• Zhiyang Zhang,
• Jialei Hu,
• Hanfeng Ding,
• Li Zhang and
• Peirong Rao

Beilstein J. Org. Chem. 2025, 21, 926–934, doi:10.3762/bjoc.21.75

• 4.4:1 mixture of regioisomeric alcohols with the desired isomer being the major component, presumably due to the considerable steric hindrance from the quaternary carbon at C4. However, decagram-scale separation of these two isomers by chromatography proved troublesome. Fortunately, the distinct

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

Substituent effects in N-acetylated phenylazopyrazole photoswitches

• Radek Tovtik,
• Dennis Marzin,
• Pia Weigel,
• Stefano Crespi and
• Nadja A. Simeth

Beilstein J. Org. Chem. 2025, 21, 830–838, doi:10.3762/bjoc.21.66

• discovered that simple acylation of the pyrazole moiety leads to increased quantum yields of isomerization, long Z-isomer life-times, good spectral separation, and high photostability. Keywords: azobenzenes; azopyrazoles; photochromism; photoswitches; substituent effects; Introduction Organic photoswitches

• reported to either bathochromically shift the UV–vis absorption spectrum or lead to a better separation of the n→π* bands of the two photoisomers and allow for visible-light-responsive switches [23][24][25][26]. In recent years, heteroaryl azobenzene derivatives have revealed superior properties to

• , such as OH or OMe, they are shifted towards the blue. Especially for NAc-PAPs, we observe a higher spectral separation of the π→π* and the n→π* transitions of the Z isomers compared to NMe-PAPs and NH-PAPs. For instance, the separation for the π→π* transition band and the n→π* is 176 nm for NAc-PAP-CN

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

• and charge separation. In the resonance forms 3a’–e’, the 4-methoxybenzylamino group is covalently attached to the 4-position of the 1,5-disubstituted pyrrolidine-2,3-dione core via a Schiff’ base (C=N) linkage in which the positive charge could be delocalized on both carbon and nitrogen atoms. In

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

• reduction occur in separate compartments, separated by a diaphragm or salt bridge, to prevent reactant mixing and improve efficiency (e.g., Daniel cell). However, in undivided cells, both reactions occur in a single compartment without separation, resulting in a more straightforward design but potentially

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

• and water [1][2][3][4]. Building on this fundamental knowledge, supramolecular chemists created a variety of functional systems including supramolecular polymers, sensing ensembles, molecular machines, supramolecular separation phases, and drug delivery systems [5][6][7][8][9]. A primary subfield of

Photochemically assisted synthesis of phenacenes fluorinated at the terminal benzene rings and their electronic spectra

• Yuuki Ishii,
• Minoru Yamaji,
• Fumito Tani,
• Kenta Goto,
• Yoshihiro Kubozono and
• Hideki Okamoto

Beilstein J. Org. Chem. 2025, 21, 670–679, doi:10.3762/bjoc.21.53

• 18-crown-6 produced fluorine-containing diarylethene 8 as a mixture of E- and Z-isomers. Subsequently, the E/Z mixture of 8 was subjected to the Mallory photoreaction without separation. Thus, compound 8 was irradiated with fluorescent black-light lamps (300 nm, 6 × 16 W) in the presence of a

Formaldehyde surrogates in multicomponent reactions

• Cecilia I. Attorresi,
• Javier A. Ramírez and
• Bernhard Westermann

Beilstein J. Org. Chem. 2025, 21, 564–595, doi:10.3762/bjoc.21.45

• separation processes are required [32][35][36]. In this context, DMSO has been used as an alternative to formaldehyde for the MCR synthesis of a wide variety of quinolines and related compounds. For example, Zhang et al. showed that starting from anilines and substituted styrenes while using K2S2O8 for the

Deep-blue emitting 9,10-bis(perfluorobenzyl)anthracene

• Long K. San,
• Sebastian Balser,
• Brian J. Reeves,
• Tyler T. Clikeman,
• Yu-Sheng Chen,
• Steven H. Strauss and
• Olga V. Boltalina

Beilstein J. Org. Chem. 2025, 21, 515–525, doi:10.3762/bjoc.21.39

• the Cu powder. The solvents were removed in vacuo producing an orange oil. 9,10-ANTH(BnF)2 was isolated via multiple stages of HPLC separation. Yield (isolated): 9-Br-10-BnF-ANTH (11%), 9,10-(BnF)2-ANTH (14%). Method 1.3 (9,10-ANTH(Br)2, Cu, PhCl): 9,10-ANTH(Br)2 (13.4 mg, 39.8 µmol) was mixed with Cu

• separation. Yield (isolated): 9-Br-10-BnF-ANTH (14%), 9,10-(BnF)2-ANTH (5%). Method 1.4 (9,10-ANTH(Br)2, Cu, NMP): 9,10-ANTH(Br)2 (13.4 mg, 39.8 µmol) was mixed with Cu powder (100 mg, 1.57 mmol) in a 10 mL rotavis reaction tube fitted with a wired septum in a glove box. NMP (5 mL) was added to the reaction

• reaction mixture was filtered to remove the Cu powder. The solvents were removed in vacuo producing an orange oil. 9,10-ANTH(BnF)2 was isolated via one stage of HPLC separation. Yield (isolated): 9-Br-10-BnF-ANTH (23%), 9,10-(BnF)2-ANTH (17%). Method 1.5 (9,10-ANTH(Br)2, Cu, PhCN): Cu (50 mg, 0.79 mmol

Synthesis of the aggregation pheromone of Tribolium castaneum

• Biyu An,
• Xueyang Wang,
• Ao Jiao,
• Qinghua Bian and
• Jiangchun Zhong

Beilstein J. Org. Chem. 2025, 21, 510–514, doi:10.3762/bjoc.21.38

• , Mori and Phillips achieved the complete separation of the derivatives from the four stereoisomers by reversed-phase HPLC at −54 °C, and revealed that the natural pheromone consists of four stereoisomers of 4,8-dimethyldecanal (Figure 1) [16][17]. Previous syntheses mainly focused on chiral sources of

Unprecedented visible light-initiated topochemical [2 + 2] cycloaddition in a functionalized bimane dye

• Metodej Dvoracek,
• Brendan Twamley,
• Mathias O. Senge and
• Mikhail A. Filatov

Beilstein J. Org. Chem. 2025, 21, 500–509, doi:10.3762/bjoc.21.37

• °) (crystallographic unit cell can be seen in Figure 6a). However, in Me2B, the bonds are further apart, with an intermolecular separation of 3.862(2) Å. Although this is still within the range for a potential reaction, no reaction was observed. In contrast, Me4B lacks the proper alignment of the reactive double bonds

Synthesis of N-acetyl diazocine derivatives via cross-coupling reaction

• Thomas Brandt,
• Pascal Lentes,
• Jeremy Rudtke,
• Michael Hösgen,
• Christian Näther and
• Rainer Herges

Beilstein J. Org. Chem. 2025, 21, 490–499, doi:10.3762/bjoc.21.36

• ) exhibit an n–π*-transition at approximately 400 nm, matching the n–π*-transition of unsubstituted N-acetyl diazocine 1 (Table 6). Irradiation with light of 405 nm gives the metastable E isomers with photoconversion yields of 76–85% due to a very good separation of the n–π*-transitions. N-Acetyl diazocine

Photomechanochemistry: harnessing mechanical forces to enhance photochemical reactions

• Francesco Mele,
• Ana M. Constantin,
• Andrea Porcheddu,
• Raimondo Maggi,
• Giovanni Maestri,
• Nicola Della Ca’ and
• Luca Capaldo

Beilstein J. Org. Chem. 2025, 21, 458–472, doi:10.3762/bjoc.21.33

• cost for photomechanochemical reactions. However, its primary limitation lies in the manual operation and the separation of the grinding and photoreaction steps. This approach affects the reproducibility of the reaction, as it depends on the energy applied by the operator. Moreover, it is time