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

• the hydrogenated product (Scheme 17E). It is noteworthy that the nature of the proton source fundamentally alters the reaction pathway, with distinct mechanistic regimes arising from differences in protonation mode, hydrogen-bonding interactions, and their impact on Ni–H insertion and β-hydride

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

• , tunable basicity, and directional hydrogen-bonding capabilities enable precise modulation of molecular recognition, biological activity, and physicochemical properties. Consequently, the efficient and selective construction of carbon–nitrogen (C–N) bonds embedded within aromatic nitrogen frameworks

Chiral cyclopropenimine-catalyzed enantioselective Michael reactions of phenol and benzofuran-derived α,β-unsaturated pyrazolamides with benzophenone-imine of glycine esters

• Ya Bai,
• Xue-Ying Wang,
• Si-Kai Zhu,
• Yan-Ting Shen,
• Sheng-Yong Zhang and
• Ping-An Wang

Beilstein J. Org. Chem. 2026, 22, 888–896, doi:10.3762/bjoc.22.69

• stereospecific ability of CSB-1. This may be due to a more flexible hydrogen-bonding donor group and a smaller steric hinderance in CSB-1 than in other cyclopropenimines to provide good hydrogen-bonding interaction in the transition state [13]. With decreasing amount of CSB-1 from 20 mol % to 10 mol %, the yield

• acetate (EA) as a solvent (Table 1, entry 14 vs entry 1). The reaction carried out in acetonitrile provided racemic 6a (Table 1, entry 15). When MeOH was used as a solvent, it led to no reaction (Table 1, entry 16), this may due to the large amount of hydrogen-bonding interactions in MeOH to inactivate

Unsymmetrical sulfoxides with sterically hindered catechol fragment: synthesis, structure, electrochemical properties, and antiradical activity

• Daria A. Burmistrova,
• Vasiliy A. Fokin,
• Oleg P. Demidov,
• Mikhail A. Kiskin,
• Maxim V. Arsenyev,
• Andrey I. Poddel’sky,
• Nadezhda T. Berberova and
• Ivan V. Smolyaninov

Beilstein J. Org. Chem. 2026, 22, 828–837, doi:10.3762/bjoc.22.65

• , respectively. A notable feature of the IR spectrum of sulfoxide 5a is the smallest shift of the OH bands (6–13 cm−1) relative to the corresponding thioether, which is attributed to the bulky adamantyl substituent. Consequently, differences in the strength of hydrogen bonding among the synthesized compounds are

• establish a coherent framework for understanding the behavior of S-functionalized catechols. The ability to control the hydrogen-bonding propensity, redox potentials, and antioxidant activity by varying the substituent at sulfur and its oxidation level opens promising avenues for the design of biomimetic

Design, synthesis, and biological evaluation of FXR/ASK1 dual-target modulators

• Xi Zhang,
• Jingyan Wang,
• Ziqiang Zhao,
• Caiyi Wang,
• Zenghui Ye,
• Wei-Yuan Ma,
• Jian-Xing Xu and
• Fengzhi Zhang

Beilstein J. Org. Chem. 2026, 22, 771–781, doi:10.3762/bjoc.22.59

• moieties of Z8 formed hydrogen bonds with the key residues ARG-331 and HIS-447, respectively. Similarly, in the ASK1 binding pocket, the isoxazole, carbonyl, and triazole groups of Z8 engaged in hydrogen bonding with residues GLY-759, VAL-757, and LYS-709, respectively. Notably, the binding sites of Z8

Rongalite addition to dienones: diastereoselectivity in cyclic sulfone synthesis; stereochemical rationalization and prospects as a general conjugate nucleophile

• Melina Goga,
• Hao Zong,
• James Franco,
• Jazmine Prana,
• Rudolph Michel,
• Antonia Muro,
• Elana Rubin,
• Janet Brenya,
• Henk Eshuis and
• Magnus W. P. Bebbington

Beilstein J. Org. Chem. 2026, 22, 742–752, doi:10.3762/bjoc.22.56

• high concentration of ≈80% acetic acid (pH ≈3), it seemed plausible that activation of the dienone carbonyl group would occur by hydrogen-bonding, rather than complete proton transfer to the carbonyl oxygen lone pairs [29]. We therefore included explicit solvation with acetic acid in our computational

Towards the targeted protein degradation of CK2: design and synthesis of CAM4066-based PROTACs

• Sophie Day-Riley,
• Sona Krajcovicova,
• Aryaman Raj Sokhal,
• Jan L. Venne,
• Paul Brear,
• Marko Hyvönen,
• Benjamin C. Whitehurst,
• Jason S. Carroll and
• David R. Spring

Beilstein J. Org. Chem. 2026, 22, 611–619, doi:10.3762/bjoc.22.47

• CK2α further confirmed, that both the ATP-binding and αD-binding motifs retained their expected hydrogen-bonding and hydrophobic interactions, and the linker projected cleanly toward solvent-exposed region (Figure 1). Importantly, the absence of the terminal alkyne substituent in the electron density

Experimental and DFT studies on the regioselective methanolysis of 5-azido-9-oxabicyclo[6.1.0]nonan-4-yl 4-nitrobenzoate isomers

• İlknur Polat,
• Selçuk Eşsiz and
• Emine Salamci

Beilstein J. Org. Chem. 2026, 22, 547–556, doi:10.3762/bjoc.22.40

• correlates well with the computed activation barriers and the divergence of the competing reaction pathways. In this context, despite the presence of a hydrogen-bonding interaction in TS2, TS1 is lower in energy due to a more favourable cyclooctane conformation. Notably, the relatively small energy

• difference between TS1 and TS2 (4.7 kcal/mol), compared to that between TS3 and TS4 (6.9 kcal/mol), can be attributed to hydrogen-bond stabilization in TS2, indicating that conformational effects play a more dominant role than hydrogen bonding in determining transition-state stability. Mulliken charge

Recent advances in the stereoselective synthesis of distal biaxially chiral molecules

• Fanxing Zhou,
• Chen Zhang,
• Lingyu Sun,
• Yiyun Fang,
• Siming Zheng,
• Lina Hu,
• Mengyang Shen,
• Zhen Zhao,
• Wei Xu,
• Yunqiang Sun and
• Zi-Qiang Rong

Beilstein J. Org. Chem. 2026, 22, 461–479, doi:10.3762/bjoc.22.34

• potential applications in ligand and catalyst development. In a complementary direction, Smith’s group achieved the highly enantioselective synthesis of axially chiral naphthamides (Scheme 6) [47]. Their strategy employed transition-state hydrogen bonding to induce substrate deracemization, followed by

Synthesis and anti-cancer activity of naphthalimide–organylselanyl conjugates

• Rajkumar Ravi and
• Selvakumar Karuthapandi

Beilstein J. Org. Chem. 2026, 22, 416–435, doi:10.3762/bjoc.22.29

• significant negative character that enables it to form a hydrogen bonding interaction with the active site amino acid residue of the proteins. MEP analysis of compounds 7 and 8 The molecular electrostatic potential (MEP) maps of compounds 7 and 8 are depicted in Figure 6a and 6b, respectively. The MEP

• regions indicate more electronegative areas. For both compounds 7 and 8, the oxygen atoms exhibit the highest electronegativity, indicating potential nucleophilicity and the ability to readily participate in hydrogen bonding with amino acids through non-covalent interactions. Overall, MEP mapping reveals

• interactions: van der Waals (Gly772), hydrogen bonding and carbon–hydrogen bonding (Met769), π–donor (Thr766), π–σ (Leu820), π–sulfur (Met742), amide–π (Phe771), alkyl (Leu694), and π–alkyl interactions (Val702, Ala719, Lys721, Leu764). In contrast, compound 8 formed eight interactions: van der Waals (Pro770

Cone p-aminocalix[4]arenes enriched with ‘clickable’ alkyne or azide functionalities

• Ilia Korniltsev,
• Vasily Bazhenov,
• Alexander Gorbunov,
• Dmitry Cheshkov,
• Stanislav Bezzubov,
• Vladimir Kovalev and
• Ivan Vatsouro

Beilstein J. Org. Chem. 2026, 22, 399–415, doi:10.3762/bjoc.22.28

• heterodimer 49·52. The spectrum clearly shows even more downfield-shifted resonances from the four NH groups involved in hydrogen bonding with the sulfonyl groups, as well as clear signals from the two AB spin systems of the methylene groups attached to the single triazole moiety, in which the protons have

• concentrations of dissolved compounds was too low for NMR analysis. Thus, additional experiments need to be designed to reveal whether the triazolated tetraureacalix[4]arenes can be used to include pairs of triazole-bound cations into supramolecules via intermolecular hydrogen bonding between the urea groups

Recent advances in the cleavage of non-activated amides

• Eun-Sol Choi and
• Hyo-Jun Lee

Beilstein J. Org. Chem. 2026, 22, 352–369, doi:10.3762/bjoc.22.23

• . Its characteristic hydrogen-bonding ability strongly influences molecular conformation and intermolecular interactions, while the exceptional thermodynamic stability of the amide moiety contributes to its persistence in diverse atmospheric and biological environments [1][2][3][4][5]. Owing to these

• state S, which is stabilized by two new hydrogen-bonding interactions. Finally, elimination of [MeNH3]MeSO4 delivers the butyl ester product. In 2025, Dou et al. developed a metal-free alcoholysis of amides mediated by HBF4, exhibiting a very broad substrate scope (Scheme 12) [60]. The esterification of

• bromine (Br2), which converts the amide into N-bromobenzamide. Meanwhile, at the cathode, the alcohol is partially deprotonated to form an alkoxide, which engages in a stabilizing hydrogen-bonding interaction to produce the acid–base pair V. Nucleophilic attack of V on N-bromobenzamide forms a tetrahedral

Spirobarbiturates with a pyrrolizidine moiety: synthesis, structure and biological evaluation

• Arthur A. Puzyrkov,
• Andrew S. Drachuk,
• Ekaterina A. Popova,
• Alexander V. Stepakov and
• Vitali M. Boitsov

Beilstein J. Org. Chem. 2026, 22, 274–288, doi:10.3762/bjoc.22.20

• (Figure 2). Both compounds crystallize as racemates, Figure 3 displaying their unit cell fragments. In 4b, the two enantiomers are connected through weak hydrogen bonds (N–H···O 2.612 Å) between the barbiturate rings. In contrast, compound 4c exhibits classical hydrogen bonding (N–H···O 1.878 Å) linking

• =O···H ≈ 3.6 Å, which is consistent with weak hydrogen-bonding interactions. In silico analyses of drug-like properties. An in silico analysis was performed to preliminarily determine whether the synthesized spiro-fused adducts have drug-like properties. The physicochemical profile was determined

Conformational analysis of difluoromethylornithine: factors influencing its gas-phase and bioactive conformations

• Matheus P. Freitas

Beilstein J. Org. Chem. 2026, 22, 237–243, doi:10.3762/bjoc.22.17

• bioconformation observed in crystallographic data corresponds to a type-II structure, imposed by strong hydrogen bonding of the amino and carboxyl groups with surrounding residues. Thus, DFMO’s intrinsic conformational preferences are dictated by stereoelectronic effects, but these can be overridden by specific

• balance shifts, since strong intermolecular interactions – especially hydrogen bonding with amino acid residues – favor a type-II geometry as the predominant bioconformation. Nevertheless, when different conformers engage in comparable intermolecular interactions, intramolecular effects such as the gauche

• )/CBS level of theory. Color labels: H = white, C = grey, N = blue, O = red, F = electric blue. (S)-DFMO bound within the active site of human arginase I obtained from the Protein Data Bank (3GN0) (https://doi.org/10.2210/pdb3gn0/pdb, [21]). Dotted lines represent hydrogen-bonding interactions with

Screwing the helical chirality through terminal peri-functionalization

• Devesh Chandra,
• Sachin and
• Upendra Sharma

Beilstein J. Org. Chem. 2026, 22, 205–212, doi:10.3762/bjoc.22.14

• enantioselectivity. Notably, [6]helicene 3k was also readily produced, via kinetic resolution (Scheme 1). Computational studies suggested that hydrogen bonding and π interactions between the reactants and catalyst L1 controlled the stereochemical output of the products 3. The catalyst proximate both reactants to

• each other via hydrogen-bonding interaction, locking the relative orientation of the substrates producing the chiral [4]carbohelicene via peri-terminal functionalization (Figure 2). To examine the utility of the developed protocol, the reaction was scaled up to a 2 mmol scale and the product was

• nucleophilic substitution reactions (Scheme 5). A stereochemical model was proposed for the phospha-Michael addition, indicating that enantioselectivity was primarily influenced by steric effects arising from hydrogen bonding and ion pairing between the peptide mimetic phosphonium salt (PPS)-activated

Improved synthesis and physicochemical characterization of the selective serotonin 2A receptor agonist 25CN-NBOH

• Adrian G. Rossebø,
• Hannah G. Kolberg,
• Anders E. Tønder,
• Louise Kjaerulff,
• Poul Erik Hansen,
• Karla A. Frydenvang,
• Jesper Østergaard and
• Jesper L. Kristensen

Beilstein J. Org. Chem. 2026, 22, 175–184, doi:10.3762/bjoc.22.11

• relatively high solubility. Intramolecular hydrogen bonding Previous pharmacokinetic investigations showed that 1 displays high permeability in the MDCK assay (apical–basal 29 × 10−6 cm/s and basal–apical 20 × 10−6 cm/s) [6], a well-established in vitro model for assessing blood–brain barrier (BBB

• isotope effect observable as changes in the 13C NMR chemical shift [18][19]. DFT calculations were based on a truncated model (Figure 6a) containing the essential elements for intramolecular hydrogen bonding. The structure was considered both in vacuum as well as with DMSO or water as implicit solvents

• performed using the Gaussian 16 software [29]. A truncated model of 1 containing the essential elements for hydrogen bonding was used (see Figure 6a). The structure was geometry-optimized in the gas phase using the B3LYP/6-31G(d,p) level of theory. The effect of the solvent was considered using the PCM

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

• available drugs [1]. These structures exhibit unique properties that influence pharmacokinetic and pharmacodynamic parameters, including lipophilicity, polarity, hydrogen-bonding capacity, and toxicological profiles [2][3][4]. Among them, five-membered multi-heterocyclic (FMMH) rings are privileged

• through intramolecular hydrogen bonding. By comparing the data for λabs and λem, it is evident that the compounds exhibit significant Stokes shifts with values above 2,100 cm−1, reflecting their stability in the excited state [87][88][89]. The highest values of Stokes shifts were observed in polar protic

Efficient solid-phase synthesis and structural characterization of segetalins A–H, J and K

• Liangyu Liu,
• Wanqiu Lu,
• Quanping Guo and
• Zhaoqing Xu

Beilstein J. Org. Chem. 2025, 21, 2612–2617, doi:10.3762/bjoc.21.202

• –220 nm and a maximum below 200 nm. CD spectroscopy revealed that cyclic topology shifts characteristic peaks and stabilizes secondary structures through cooperative ring size/sequence/solvent effects [30]. TFE disrupts the hydrogen-bonding network of water, reduces solvent polarity, and enhances the

Visible-light-driven NHC and organophotoredox dual catalysis for the synthesis of carbonyl compounds

• Vasudevan Dhayalan

Beilstein J. Org. Chem. 2025, 21, 2584–2603, doi:10.3762/bjoc.21.200

• process, such as being environmentally friendly, offering operational simplicity, lower cost, and easy availability, reducing waste and toxicity, as well as providing excellent chemo-, regio-, and enantioselectivity through fine-tuned hydrogen bonding or covalent activation modes. Furthermore, the

Isoorotamide-based peptide nucleic acid nucleobases with extended linkers aimed at distal base recognition of adenosine in double helical RNA

• Grant D. Walby,
• Brandon R. Tessier,
• Tristan L. Mabee,
• Jennah M. Hoke,
• Hallie M. Bleam,
• Angelina Giglio-Tos,
• Emily E. Harding,
• Vladislavs Baskevics,
• Martins Katkevics,
• Eriks Rozners and
• James A. MacKay

Beilstein J. Org. Chem. 2025, 21, 2513–2523, doi:10.3762/bjoc.21.193

• possible base pairs (G–C, A–U, C–G, and U–A). Notably, each synthetic nucleobase takes advantage of favorable hydrogen bonding interactions to the proximal nucleobase in the Watson–Crick base pair. Strong binding has been reported for purine recognition given the propensity for two Hoogsteen hydrogen bonds

• single hydrogen bond [29][30]. In efforts toward improving pyrimidine recognition, several groups have explored PNA nucleobase monomers using extended nucleobases to utilize maximum hydrogen bonding interactions across the Hoogsteen face of the Watson–Crick base pair [13][15]. Notable examples of the PNA

• recognize U–A without formally hydrogen-bonding to U. This distal base recognition approach utilized design elements of our previous Io series [35][36], particularly Io5 chosen for its synthetic simplicity and the ability to further functionalize the aromatic phenyl group. Three new nucleobases, Db1, Db2

Catalytic enantioselective synthesis of selenium-containing atropisomers via C–Se bond formations

• Qi-Sen Gao,
• Zheng-Wei Wei and
• Zhi-Min Chen

Beilstein J. Org. Chem. 2025, 21, 2447–2455, doi:10.3762/bjoc.21.186

• .1 initially engages substrate 7 through hydrogen bonding, forming intermediate Int 7. Subsequently, deprotonation of the naphthol group by quinuclidine yields intermediate Int 8. This intermediate then undergoes nucleophilic attack on the selenium atom in substrate 8, leading to the formation of the

• (Scheme 4). In 2025, Yang, Lu, and co-workers employed bifunctional catalysts, including chiral thiourea derivatives or chiral phosphoric acid, to activate alkynes and selenols through multiple hydrogen-bonding interactions, thereby achieving an enantioselective hydroselenation of alkynes [22]. All

The high potential of methyl laurate as a recyclable competitor to conventional toxic solvents in [3 + 2] cycloaddition reactions

• Ayhan Yıldırım and
• Mustafa Göker

Beilstein J. Org. Chem. 2025, 21, 2389–2415, doi:10.3762/bjoc.21.184

• but not limited to methyl laurate, has found application in a variety of direct and indirect food additive applications [94]. The Hansen solubility parameter is a numerical expression that quantifies a molecule's cohesive energy density from non-polar, polar, and hydrogen-bonding interactions. It is a

• space is shown in Figure 8a. The distribution of these selected solvents with other organic solvents in the 3D Hansen solubility space is determined by three Hansen solubility parameters (HSPs): dispersion (δD), polarity (δP), and hydrogen bonding (δH). As is well established, information about their

• potential hazard associated with their utilization as a solvent in the aforementioned reactions. For the solute component C,N-diphenylnitrone, the dispersion, polarity, and hydrogen bonding values for nitrone were determined as δD = 16.6, δP = 7.6 and δH = 8.7. Figure 8b clearly shows the position of the

Conformational effects on iodide binding: a comparative study of flexible and rigid carbazole macrocyclic analogs

• Guang-Wei Zhang,
• Yong Zhang,
• Le Shi,
• Chuang Gao,
• Hong-Yu Li and
• Lei Xue

Beilstein J. Org. Chem. 2025, 21, 2369–2375, doi:10.3762/bjoc.21.181

• mechanism, while rigid WDGs are limited by the preorganization effect and can only achieve weak hydrogen bonding through conformational selection. In addition, the changes in the chemical shifts of the above two structures lead us to believe that the two structural analogs undergo conformational changes

Rotaxanes with integrated photoswitches: design principles, functional behavior, and emerging applications

• Jullyane Emi Matsushima,
• Khushbu,
• Zuliah Abdulsalam,
• Udyogi Navodya Kulathilaka Conthagamage and
• Víctor García-López

Beilstein J. Org. Chem. 2025, 21, 2345–2366, doi:10.3762/bjoc.21.179

• –guest interaction induces a chiral signal, while the azobenzene chromophore imparts photoswitching properties to the molecule. Furthermore, solvent-mediated hydrogen-bonding interactions tailored within the inner cyclodextrin cavity, combined with photocontrolled isomerization of the azo moiety, enable

• form selective hydrogen bonds between the carbonyl oxygen of the fumaramide unit and the N–H groups of benzylic amide rings. Upon isomerization to the cis isomer, the hydrogen-bonding interactions are weakened, enabling the macrocycle to migrate to a second recognition station [61]. Despite their

• site, enabling precise control over molecular motion [71]. The incorporation of pyridyl-acyl hydrazone units is demonstrated to enable high binding (>95%) and reversible macrocycle shuttling between two binding sites (98%). Moreover, structural analysis revealed distinct intercomponent hydrogen-bonding

Enantioselective radical chemistry: a bright future ahead

• Anna C. Renner,
• Sagar S. Thorat,
• Hariharaputhiran Subramanian and
• Mukund P. Sibi

Beilstein J. Org. Chem. 2025, 21, 2283–2296, doi:10.3762/bjoc.21.174

• , transition-metal catalysis, and enzyme catalysis. Progress in enantioselective reactions using these approaches is discussed with the help of one or two examples in each category to highlight the outstanding achievements in the past three decades. Other modes of catalysis relying on hydrogen-bonding [13][14

• current limitations in the scope and capabilities of enantioselective radical chemistry. The existing literature features a predominant use of nucleophilic radicals, a small number of H-atom donors, and limited application of hydrogen-bonding catalysis in radical reactions. Further studies on

• enantioselective transformations of electrophilic radicals, alternative H-atom sources, and additional modes of catalysis (including hydrogen-bonding catalysis) would be valuable. Additionally, the development of more efficient methods, using lower catalyst loadings, remains an important goal for ongoing research