Electrochemical reduction of unsaturated carbon–carbon bonds via 3d transition-metal catalysis

• Geon Kang,
• Minki Jeon,
• Pooja Kumari Jat,
• Cheoljae Kim and
• Isaac Choi

Beilstein J. Org. Chem. 2026, 22, 955–981, doi:10.3762/bjoc.22.75

• , controllable reaction manifolds that are inaccessible under thermochemical conditions. These developments position 3d metal electrocatalysis as a versatile and programmable platform for selective hydrogenation and isotopic labeling under mild, sustainable conditions. Keywords: electrochemical reduction

• -induced preorganization that enables inner-sphere proton-transfer steps and thereby enforces Z-selectivity. Notably, electrochemical reduction further offers a compelling platform for selective deuterium incorporation, as isotopic labeling can be achieved directly from simple deuterium sources under

• experimental evidence that the reaction does not proceed through a radical pathway (Scheme 17C). In addition, deuterium-labeling studies using deuterated proton sources revealed selective incorporation of deuterium at the benzylic position of the product, supporting the involvement of a Ni–H intermediate

Synthesis of sterically shielded piperidine nitroxides via acid-catalyzed heterocyclization of β-aminoketone derivatives with ketones

• Mark M. Gulman,
• Yurii I. Glazachev and
• Sergey A. Dobrynin

Beilstein J. Org. Chem. 2026, 22, 948–954, doi:10.3762/bjoc.22.74

• significant practical importance. Their applications range widely, from fundamental research to industrial technologies. In the spin-labeling technique, these radicals have been extensively used in biophysics and structural biology [1]. Piperidine-based radicals were the first used for measuring distances in

Recent advances in copper-catalyzed direct hydroamination of alkenes with (hetero)aromatic amines

• Hyejeong Lee and
• Yunmi Lee

Beilstein J. Org. Chem. 2026, 22, 925–947, doi:10.3762/bjoc.22.73

• . Radical trapping experiments and deuterium labeling studies supported the involvement of radical intermediates and solvent-derived hydrogen atom transfer steps in the catalytic cycle. This study highlights the dual role of copper as a photocatalyst and coupling catalyst, enabling hydroamination under mild

• smoothly with styrene derivatives 52 to afford the corresponding Markovnikov hydroamination products 53 in moderate to good yields. Mechanistic investigations have suggested that the transformation proceeded via a radical pathway rather than a classical ionic hydroamination process. Deuterium-labeling

A practical CO₂-mediated synthesis of 5,6-carboxylated silicon-rhodamines for targeted probe development

• Dongjie Hou,
• Shaowei Wu,
• Ning Xu,
• Pengjun Bao,
• Wenhao Jia,
• Qinglong Qiao and
• Zhaochao Xu

Beilstein J. Org. Chem. 2026, 22, 915–924, doi:10.3762/bjoc.22.72

• variety of intracellular proteins, including histone H2B, Sox2, vimentin, clathrin, and ensconsin [15][16][39], underscoring the broad utility of this labeling strategy for protein-specific imaging. Subsequently, the 4c probe obtained through our one-pot strategy was applied to SIM imaging of multiple

Site-specific labelling of native peptides and proteins: chemical and enzymatic strategies

• Antonio Angelastro,
• Jonathan Bargh,
• Subhajit Guria,
• Victor Laserna and
• Louis Luk

Beilstein J. Org. Chem. 2026, 22, 857–881, doi:10.3762/bjoc.22.67

• -modification market is expected to reach USD 6.02 billion by 2034 (https://www.towardshealthcare.com/insights/protein-labeling-market-sizing). Review Key criteria for effective native-sequence modifications Effective protein modification relies on tools that balance three interlinked factors translating basic

Hydrogen production from formic acid catalyzed by NHC–Cu complexes

• Orlando Santoro and
• Catherine S. J. Cazin

Beilstein J. Org. Chem. 2026, 22, 620–627, doi:10.3762/bjoc.22.48

• decomposition in the presence of PhSiH3 was investigated. Surprisingly, gas-chromatography analyses showed that only H2 was released. Remarkably, neither CO nor CO2 were detected (see Supporting Information File 1, section 5). To obtain more information on the mechanism of this reaction, isotopic labeling

• simultaneous occurrence of two dehydrogenative mechanisms can explain the results of the isotopic labeling experiments. Indeed, while HD arises from the coupling of HCO2D with phenylsilane, the formation of H2 takes place by dehydrogenative coupling of the hydrosilanes present in the reaction mixture. To

• labeling experiments. Proposed catalytic cycle for the NHC–Cu-catalyzed FA dehydrogenation. Dehydrogenative coupling of phenylsilane. Catalyst optimization.a Optimization of the amine.a Influence of the size of the amine on the dehydrogenation of FA/amine mixtures. Supporting Information Supporting

Synthesis of a HDAC inhibitor–nanogold probe for cryo-EM visualization in class I HDAC co-repressor complexes

• Wiktoria A. Pytel,
• John W. R. Schwabe and
• James T. Hodgkinson

Beilstein J. Org. Chem. 2026, 22, 480–485, doi:10.3762/bjoc.22.35

• localization within a cell, as well as in cellular cryo-electron tomography [11][12]. More recently, gold nanoparticles have been used as labeling tools in vitrified cells to locate cellular compartments in cellular cryo-EM [13]. Given the considerable utility of nanogold particles in microscopy, we aimed to

• stoichiometric conjugation with suitable substrates. The small size of Au–NH2 minimizes steric hindrance and allows for enhanced spatial resolution, relative to colloidal nanogold particles, thereby facilitating high precision labeling of the HDAC active site. CI-994 was synthesized using previously established

Structural reassignment of compound 968, an allosteric glutaminase inhibitor

• Lindsey A. Albertelli,
• Sainabou Jallow,
• Chun Li and
• Scott M. Ulrich

Beilstein J. Org. Chem. 2026, 22, 455–460, doi:10.3762/bjoc.22.33

• inhibits glutaminase by covalently labeling the catalytic serine [8]. DON inhibits other glutamine-utilizing enzymes such as asparagine synthetase and has activity against a wide range of cancer cell lines [9][10]. BPTES is a potent allosteric inhibitor of GAC/KGA that binds at the dimer–dimer interface

Thiazolidinones: novel insights from microwave synthesis, computational studies, and potentially bioactive hybrids

• Luan A. Martinho,
• Victor H. J. G. Praciano,
• Guilherme D. R. Matos,
• Claudia C. Gatto and
• Carlos Kleber Z. Andrade

Beilstein J. Org. Chem. 2025, 21, 2618–2636, doi:10.3762/bjoc.21.203

• : a) 1H NMR spectra (600 MHz, DMSO-d6) with expansions, and b) 13C NMR spectra (151 MHz, DMSO-d6) with expansions. a) Molecular structure of 3n with crystallographic labeling (50% probability displacement). b) Perspective views of intermolecular hydrogen bonds (dotted lines) of 3n. (‘) symmetry

Understanding the origin of stereoselectivity in the photochemical denitrogenation of 2,3-diazabicyclo[2.2.1]heptene and its derivatives with non-adiabatic molecular dynamics

• Leticia A. Gomes and
• Steven A. Lopez

Beilstein J. Org. Chem. 2025, 21, 2007–2020, doi:10.3762/bjoc.21.156

• ]. The experimental studies on the thermal denitrogenation of diazabicyclo[2.1.1]hep-2-ene (DBH, 1) indicate that both the parent compound and its derivatives undergo a concerted elimination of N2 and the inverted product (exo-2) is preferentially formed [55][56]. Deuterium labeling of DBH was employed

Fe-catalyzed efficient synthesis of 2,4- and 4-substituted quinolines via C(sp²)–C(sp²) bond scission of styrenes

• Prafull A. Jagtap,
• Manish M. Petkar,
• Vaishnavi R. Sawant and
• Bhalchandra M. Bhanage

Beilstein J. Org. Chem. 2025, 21, 1799–1807, doi:10.3762/bjoc.21.142

• reaction mixture was stirred at 120 °C for 24 hours, resulting in the formation of 27% of 3a along with 33% of 3a′. To further investigate the role of the solvent in the reaction mechanism, a deuterium-labeling experiment was performed by reacting 1a with 2a in deuterated methanol (CD3OD) under standard

Influence of the cation in hypophosphite-mediated catalyst-free reductive amination

• Natalia Lebedeva,
• Fedor Kliuev,
• Olesya Zvereva,
• Klim Biriukov,
• Evgeniya Podyacheva,
• Maria Godovikova,
• Oleg I. Afanasyev and
• Denis Chusov

Beilstein J. Org. Chem. 2025, 21, 1661–1670, doi:10.3762/bjoc.21.130

• check the reduction pathway D-labeling experiments were carried out. The experiments with D3PO2 illustrated that D-atoms were distributed between α- and β-positions to nitrogen in the product in case of both reduction of enamine and reductive amination of cyclohexanone with morpholine (Scheme 4a

Azide–alkyne cycloaddition (click) reaction in biomass-derived solvent Cyrene^TM under one-pot conditions

• Zoltán Medgyesi and
• László T. Mika

Beilstein J. Org. Chem. 2025, 21, 1544–1551, doi:10.3762/bjoc.21.117

• pharmaceutical ingredients (APIs) [8][9][10][11] and pesticides [12], or metabolic labeling molecules in plant science [13], to name a few important applications. The CuAAC reactions can be easily carried out under mild reaction conditions and exhibit excellent functional group tolerance [7]. While water has

Recent advances in oxidative radical difunctionalization of N-arylacrylamides enabled by carbon radical reagents

• Jiangfei Chen,
• Yi-Lin Qu,
• Ming Yuan,
• Xiang-Mei Wu,
• Heng-Pei Jiang,
• Ying Fu and
• Shengrong Guo

Beilstein J. Org. Chem. 2025, 21, 1207–1271, doi:10.3762/bjoc.21.98

• the trend C–I > C–Br > C–Cl, consistent with bond dissociation energies (90g–j). Notably, deuterated chloroform was successfully employed to obtain deuterated oxindole 90k in high yield, demonstrating the method's potential for isotope labeling applications. A plausible mechanism, as outlined in

Synthesis of HBC fluorophores with an electrophilic handle for covalent attachment to Pepper RNA

• Raphael Bereiter and
• Ronald Micura

Beilstein J. Org. Chem. 2025, 21, 727–735, doi:10.3762/bjoc.21.56

• )cyanophenylacetonitrile) fluorophores for easy access, which will contribute to the rapid dissemination of the RNA imaging approaches associated therewith. Keywords: covalent RNA labeling; FLAP; fluorophore synthesis; HBC530; self-alkylating ribozymes; Introduction The discovery of fluorescent reporters, such as green

• fluorophores also exhibited favorable solubility compared to the other functionalizations which is a critical aspect for applications in the cell. We also note that primary alkyl halides, and in particular, the mesyloxy alkyl handles presented here, are relatively underexplored for covalent labeling of nucleic

• used, although often with limited success. We believe that the electrophilic warheads presented here offer an excellent balance between reactivity and selectivity for labeling of nucleic acids, and therefore, may also stimulate new designs for RNA targeting and RNA drugging. Experimental General

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

• conditions render this method attractive for constructing complex chiral molecular architectures. A plausible mechanistic pathway for this cascade asymmetric hydroboration and hydroallylation of alkynes was proposed based on a series of control experiments, including deuterium-labeling experiments and DFT

• interactions and enhanced electronic stabilization through lithium coordination. This explains the critical role of lithium in achieving a high enantioselectivity. Isotope-labeling experiments using 10B-enriched 1,1-diborylalkanes (S)-49 further supported this mechanism, showing a stereoinvertive

• operative, deuterium-labeling studies were conducted using an enantioenriched, isotopically labeled allylic bromide (S)-54 (61:39 er) and 1,1-diborylethane 52a under optimized reaction conditions (Scheme 19a). The resulting product 55 formed with 39:61 E/Z selectivity, indicating an anti-SN2' oxidative

Photocatalyzed elaboration of antibody-based bioconjugates

• Marine Le Stum,
• Eugénie Romero and
• Gary A. Molander

Beilstein J. Org. Chem. 2025, 21, 616–629, doi:10.3762/bjoc.21.49

• different molecules, such as a drug and a targeting moiety. This technique has been shown to be useful in applications such as cell labeling, protein–protein interactions, and photoradiosynthesis of bioconjugates, but the most important challenge remains the lack of specificity to target one amino acid, and

• facilitate various modifications, including labeling, crosslinking, and the creation of protein–drug conjugates. The incorporation of photoredox strategies has facilitated the synthesis of complex protein architectures, enabling precise control over conjugation sites and degrees of modification. The number

Synthesis of electrophile-tethered preQ₁ analogs for covalent attachment to preQ₁ RNA

• Laurin Flemmich and
• Ronald Micura

Beilstein J. Org. Chem. 2025, 21, 483–489, doi:10.3762/bjoc.21.35

• an electrophilic handle for the covalent attachment of the ligand to the RNA. The simplicity of the underlying design of irreversibly bound ligand–RNA complexes has provided a new impetus in the fields of covalent RNA labeling and RNA drugging. Here, we present short and robust synthetic routes for

• biotechnological applications, including the identification of queuosinylation sites in cellular RNA [13], RNA and DNA labeling [14][15], and mRNA photocaging [16]. The latter applications rely on the promiscuity of the tRNA-modifying enzyme tRNA-guanine transglycosylase (TGT), which can incorporate functionalized

• preQ1 congeners into oligonucleotide strands at specific recognition sites. In addition, the potential of modified preQ1 for protein enzyme-independent RNA labeling has also been demonstrated [12][17]. In a recent study [4], sequence-specific RNA–small molecule crosslinking (Scheme 1B) was achieved in

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

Copper-catalyzed yne-allylic substitutions: concept and recent developments

• Shuang Yang and
• Xinqiang Fang

Beilstein J. Org. Chem. 2024, 20, 2739–2775, doi:10.3762/bjoc.20.232

• , 50a–l) axial chirality in remarkable enantiopurities. Mechanistic studies and deuterium labeling experiments have revealed that the reaction proceeds in a stepwise manner without involving a 1,5-H migration process. Based on these findings, the authors have proposed a mechanism wherein the

Machine learning-guided strategies for reaction conditions design and optimization

• Lung-Yi Chen and
• Yi-Pei Li

Beilstein J. Org. Chem. 2024, 20, 2476–2492, doi:10.3762/bjoc.20.212

• domain-adaptive encoder, ChemBERT, which was pretrained on an unlabeled corpus of ≈200k chemical journal articles. They then finetuned ChemBERT on a small annotated dataset for reaction role labeling, resulting in ChemRxnBERT, which can identify the reaction transformation and distinguish reactants

Improved deconvolution of natural products’ protein targets using diagnostic ions from chemical proteomics linkers

• Andreas Wiest and
• Pavel Kielkowski

Beilstein J. Org. Chem. 2024, 20, 2323–2341, doi:10.3762/bjoc.20.199

• background from total protein present in the lysate. The detection can be done in several different ways. To obtain an overview of how many proteins are labeled in total and what is the intensity of the labeling, the probe–protein–tag conjugates are separated on sodium dodecyl sulfate polyacrylamide gel (SDS

• the TAMRA-azide yields a mixture of labeled and unlabeled proteins. The proteins are then separated on SDS-PAGE by their molecular weight and fluorescence of the labeled proteins is recorded (Figure 6A). Due to the high sensitivity of fluorescence read-out, this allows to identify protein labeling

• probe–protein interactions are not detected because of the denaturing conditions of the SDS-PAGE. Alternatively, the fidelity of the probe labeling can be tested by a competition experiment, in which the parent compound lacking a bioorthogonal tag is used at increasing concentration to outcompete the

Deuterated reagents in multicomponent reactions to afford deuterium-labeled products

• Kevin Schofield,
• Shayna Maddern,
• Yueteng Zhang,
• Grace E. Mastin,
• Rachel Knight,
• Wei Wang,
• James Galligan and
• Christopher Hulme

Beilstein J. Org. Chem. 2024, 20, 2270–2279, doi:10.3762/bjoc.20.195

• three-component reaction of α-amino-heterocycles, aldehydes, and isocyanides which affords various aza-bicyclic molecules [48][49][50][51][52]. The methodology has been widely used for file enhancement purposes. Three deuterated GBB products are presented, Scheme 9. Unlike the previous MCRs, labeling

• this position was thought a reasonable approach to extend drug t1/2 through exploitation of the kinetic isotope effect underpinned by the C–D bond being slightly shorter and stronger than a C–H bond. Such site-specific labeling was hypothesized to slow CYP3A4 metabolism. To evaluate the hypothesis

Metal-free double azide addition to strained alkynes of an octadehydrodibenzo[12]annulene derivative with electron-withdrawing substituents

• Naoki Takeda,
• Shuichi Akasaka,
• Susumu Kawauchi and
• Tsuyoshi Michinobu

Beilstein J. Org. Chem. 2024, 20, 2234–2241, doi:10.3762/bjoc.20.191

• high efficiency under physiologically active conditions and the absence of any toxic metal ions. SpAAC is biorthogonal, which allows for the specific labeling and imaging of biomolecules even in living cells and organisms. Recently, a more rapid click reaction was desired and the strain-promoted

Transition-metal-catalyst-free electroreductive alkene hydroarylation with aryl halides under visible-light irradiation

• Kosuke Yamamoto,
• Kazuhisa Arita,
• Masami Kuriyama and
• Osamu Onomura

Beilstein J. Org. Chem. 2024, 20, 1327–1333, doi:10.3762/bjoc.20.116

• hydroarylation product was not observed (Scheme 3b). This result strongly supported the involvement of radical intermediates in the present transformation. Next, a deuterium-labeling experiment was conducted to elucidate the H-source of this reaction (Scheme 3c). The reaction of 1a and 2e in MeCN with D2O