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

• suppressing undesired side reactions, most notably hydrogen evolution reactions (HER) (Scheme 12A) [126]. This catalytic platform enabled selective semihydrogenation of both internal and terminal alkynes, including unactivated substrates, with broad tolerance toward heterocycles and alcohol functionalities

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

• Hyejeong Lee Yunmi Lee College of Pharmacy, Duksung Women’s University, Seoul 01369, Republic of Korea Department of Chemistry, Kwangwoon University, Seoul 01897, Republic of Korea 10.3762/bjoc.22.73 Abstract Nitrogen-containing aromatic amines and aza-heterocycles are ubiquitous motifs in

• ; hydroamination; N-heterocycles; Introduction Nitrogen-containing aromatic compounds, particularly aromatic amines and aza-heterocycles, are indispensable structural motifs in pharmaceuticals, agrochemicals, natural products, and advanced functional materials [1][2][3][4]. Their unique electronic characteristics

• aza-heterocycles often exhibit attenuated nucleophilicity, distinct acidity profiles, and potential coordination to metal centers, all of which can significantly influence catalytic reactivity and selectivity [20]. Therefore, the development of catalytic systems that can accommodate the unique

Palladium-catalyzed benzocyclization reactions of quinoline-2-carboxamides via sequential C–H/N–H functionalization

• Shoichi Sugita,
• Kentaro Okano and
• Atsunori Mori

Beilstein J. Org. Chem. 2026, 22, 905–914, doi:10.3762/bjoc.22.71

• ]. Additionally, intramolecular C–H arylation reactions with N-heteroaromatics can be used to synthesize various functional molecules that serve as ligands for metal extraction [36][37][38][39][40][41]. Our group developed a cyclization reaction for the intramolecular C–H arylation with N-heterocycles, such as

Cascade transformation of 2-(diazoacetyl)-2H-azirines to 2-aroyl-3-hydroxy-1H-pyrroles via condensation with aromatic aldehydes

• Timur O. Zanakhov,
• Ekaterina E. Galenko,
• Mikhail S. Novikov and
• Alexander F. Khlebnikov

Beilstein J. Org. Chem. 2026, 22, 897–904, doi:10.3762/bjoc.22.70

• essentially binary synthetic building blocks consisting of a highly strained small ring and an active functional group that are capable of reacting in domino or orthogonal modes. This dual reactivity allows their use in the syntheses of monocyclic heterocycles [11][12][13][14], fused heterocycles [15][16][17

Synthesis and structural elucidation of a novel bis-spirooxindole from isatin and ethylenediamine

• Irene Moreno-Gutiérrez,
• Josefa L. López-Martínez,
• Sonia Berenguel-Gómez,
• Irene Torres-García,
• Duane Choquesillo-Lazarte,
• Manuel Muñoz-Dorado,
• Miriam Álvarez-Corral and
• Ignacio Rodríguez-García

Beilstein J. Org. Chem. 2026, 22, 813–820, doi:10.3762/bjoc.22.63

• , the design and synthesis of spiro-heterocycles – especially spirooxindoles – has continued to expand due to their broad pharmacological relevance and the wide array of modern synthetic strategies now available for their construction, including metal-free, organocatalytic, and transition-metal-mediated

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

• heterocycles and also those looking to use Rongalite as a source of nucleophilic sulfur in other transformations. We are currently examining extensions of this method and other sulfinate reaction development and catalysis. Rongalite as an equivalent of the unstable hyposulfite ion. Sulfone diastereomers 1a and

Synthesis of heterocycles based on azomethine ylides from α-amino acids (or amines) and carbonyl compounds

• Ekaterina V. Berezhnaya,
• Alexander I. Ponyaev,
• Vitali M. Boitsov and
• Alexander V. Stepakov

Beilstein J. Org. Chem. 2026, 22, 705–741, doi:10.3762/bjoc.22.55

• using benzyl alcohols as aldehyde precursors to prepare fused heterocycles [84]. The authors note that the iridium-catalyzed oxidation of benzyl alcohol 108 to the corresponding aldehyde initially occurs. This is followed by condensation of the aldehyde with proline (103) and subsequent decarboxylation

• spiro-fused heterocycles 116–122 in high yields (Scheme 42). When examining the reaction mechanism, the authors proposed that the first step involves the condensation of phenylenediamine and ninhydrin to form indenoquinoxalin-11-one, which then reacts with proline to yield azomethine ylide. The latter

Photoorganocatalytic trifluoromethylation of (het)arenes in green conditions

• Egor N. Boronin,
• Svetlana E. Kaurkina,
• Milena M. Svetlakova,
• Anton S. Bolshakov,
• Maxim V. Arsenyev,
• Vasilii F. Otvagin,
• Alexey Yu. Fedorov,
• Timothy Noël and
• Alexander V. Nyuchev

Beilstein J. Org. Chem. 2026, 22, 662–671, doi:10.3762/bjoc.22.50

• anisoles and methylanisoles (Scheme S3, Supporting Information File 1). Substrates bearing strongly electron-withdrawing substituents and heterocycles furnished products 24–30 in low and moderate yields. Finally, caffeine underwent trifluoromethylation at a single position to give product 31 in 27% yield

Regioselective approach to 5-arylsulfonylisoxazoles and their antimicrobial activity

• Artem S. Sazonov,
• Dmitry A. Vasilenko,
• Denis V. Porfiriev,
• Yuri K. Grishin,
• Rimma A. Gazzaeva,
• Alisa P. Chernyshova,
• Maxim A. Kryakvin,
• Anna A. Baranova,
• Vera A. Alferova and
• Elena B. Averina

Beilstein J. Org. Chem. 2026, 22, 592–602, doi:10.3762/bjoc.22.45

• -inflammatory, for the treatment of Alzheimer diseases, etc. [10][11][12][13][14][15][16]. Among the sulfonyl-containing heterocycles with confirmed efficacy against microorganisms (bacteria and fungi), sulfonylisoxazoles have attracted considerable attention as potential antibacterial drugs, with the isoxazole

• determined, employing amphotericin B, vancomycin, ampicillin and clotrimazole as reference standards (Table 2). It was found, that most active isoxazole derivatives contain a nitro group in position 3 of the isoxazole cycle. Among 5-sulfonylisoxazoles, 3-nitro-substituted heterocycles 3g–k exhibited potent

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

• tetraureacalix[4]arenes was obtained. Examination of the 1H NMR spectra of the tetraureas in CDCl3 showed that in most cases triazole heterocycles do not intervene the formation of homo- and heterodimeric capsules by these compounds. Thus, considering the synthetic value of CuAAC and amine transformations, p

• ., chloroform) with the inclusion of one of the solvent molecules into the capsules. However, triazole heterocycles attached to the calixarene core can serve as weak hydrogen-bond acceptors [99] and thus may interfere with capsule formation, including the exclusive formation of heterodimeric capsules from the

• exclusive formation of heterocapsular assemblies, which was thus not hindered by the two triazole heterocycles arranged at the narrow rim of the calixarene core. Except for a slight broadening of the signals caused by the limited solubility of the compound, the 1H NMR spectrum obtained for a CDCl3 solution

Design, synthesis and biological evaluation of 2,5-diaryloxazolo[4,5-d]pyrimidin-7-ylamines as selective cytotoxic agents against HeLa cells

• Maryna V. Kachaeva,
• Agnieszka B. Olejniczak,
• Marta Denel-Bobrowska,
• Victor V. Zhirnov,
• Yevheniia S. Velihina,
• Stepan G. Pilyo and
• Volodymyr S. Brovarets

Beilstein J. Org. Chem. 2026, 22, 390–398, doi:10.3762/bjoc.22.27

• activity. They combine purine-like recognition features with the synthetic flexibility of heterocycles, offering a platform for selective targeting of tumor-related enzymes and receptors. Tumor cells overexpress kinases, DNA/RNA polymerases, and metabolic enzymes that bind purine nucleotides. Cancer cell

• pairs) can increase water solubility and facilitate salt formation. Introducing amino groups into heterocycles can have a significant impact on the anticancer activity of a compound [4][5]. Many studies have investigated the anticancer potential of heterocycle derivatives containing cytisine, glucamine

Electrosynthetic access to unsymmetrical oxaza[8]helicenes with high chiral stability and strong circularly polarized luminescence (CPL)

• Tin Zar Aye,
• Rubal Sharma,
• Muthu Karuppasamy,
• Daiya Suzuki,
• Haruka Nakajima,
• Yoshitane Imai,
• Mitsuhiro Arisawa,
• Mohamed S. H. Salem and
• Shinobu Takizawa

Beilstein J. Org. Chem. 2026, 22, 372–382, doi:10.3762/bjoc.22.25

• resulting plots show a clockwise diatropic current along the fused heterocycles and benzene rings, in agreement with the ring-current patterns reported for other helicene scaffolds [27] (Figure 2B). Enantiomerization barriers of oxaza[7]helicenes To investigate the enantiomerization (P/M) barriers of oxaza

Base-promoted deacylation of 2-acetyl-2,5-dihydrothiophenes and their oxygen-mediated hydroxylation

• Vladimir G. Ilkin,
• Margarita Likhacheva,
• Igor V. Trushkov,
• Tetyana V. Beryozkina,
• Vera S. Berseneva,
• Vladimir T. Abaev,
• Wim Dehaen and
• Vasiliy A. Bakulev

Beilstein J. Org. Chem. 2026, 22, 192–204, doi:10.3762/bjoc.22.13

• migration in the formed tetrahedral intermediate to afford formate ester; c) hydrolysis of the latter to form phenols [28]. The development of methods for the construction of heterocycles and their modification is an important area of organic synthesis [29]. Although the Dakin oxidation has become a

• convenient tool for the preparation of phenols from aromatic ketones, several specific approaches have been developed for the synthesis of hydroxylated heterocycles [30][31][32][33][34]. The deacylation of ketones is also another important direction of their transformation [35][36][37][38]. Dihydrothiophenes

Total synthesis of natural products based on hydrogenation of aromatic rings

• Haoxiang Wu and
• Xiangbing Qi

Beilstein J. Org. Chem. 2026, 22, 88–122, doi:10.3762/bjoc.22.4

• utility in complex molecule synthesis. Saturated heterocycles containing sp3-hybridized carbons play a pivotal role in natural products as well as pharmaceutical agents, as their three-dimensional structures enable more precise interactions in biological systems [24]. Among the various strategies to

• both homogeneous and heterogeneous systems, the hydrogenation of (hetero)arenes has become a cornerstone of modern synthesis for constructing saturated carbocycles and heterocycles [37]. When an appropriate ligand is paired with a transition-metal catalyst, stereoselective hydrogenation of aromatic

• highlights representative examples that illustrate recent synthetic advances [35][36]. Hydrogenation of monocyclic aromatic rings Hydrogenation of heterocyclic aromatic rings: Despite the widespread application of six-membered aromatic heterocycles in various fields of organic chemistry, reports on their

Synthesis and applications of alkenyl chlorides (vinyl chlorides): a review

• Daniel S. Müller

Beilstein J. Org. Chem. 2026, 22, 1–63, doi:10.3762/bjoc.22.1

Competitive cyclization of ethyl trifluoroacetoacetate and methyl ketones with 1,3-diamino-2-propanol into hydrogenated oxazolo- and pyrimido-condensed pyridones

• Svetlana O. Kushch,
• Marina V. Goryaeva,
• Yanina V. Burgart,
• Marina A. Ezhikova,
• Mikhail I. Kodess,
• Pavel A. Slepukhin,
• Alexandrina S. Volobueva,
• Vladimir V. Zarubaev and
• Victor I. Saloutin

Beilstein J. Org. Chem. 2025, 21, 2716–2729, doi:10.3762/bjoc.21.209

• starting substrates in multicomponent syntheses [17][18][19]; at the same time, they often show extraordinary reactivity. For example, the introduction of polyfluoroalkyl-3-oxo esters into the aforementioned Hantzsch and Biginelli reactions leads to the hydrated heterocycles, which can provide insight into

• functional group, the presence of which should affect their diastereomeric structure. We have found only one work describing the use of 1,3-diaminopropan-2-ol to form heterocycles, where it is reported to react with chloroacetaldehyde and carbon dioxide as an N,N-dinucleophile only, giving hexahydro[1,3

• –1628 cm−1 and NH2 groups at ν 3376–3272 cm−1. The structures of the obtained heterocycles 4 and 5 contain three stereocenters, so one could expect the formation of up to 8 stereoisomers in each case. Analysis of the 19F NMR spectra showed that from two to four diastereomers of

Tandem hydrothiocyanation/cyclization of CF₃-iminopropargyl alcohols with NaSCN in the presence of AcOH

• Ruslan S. Shulgin,
• Ol’ga G. Volostnykh,
• Anton V. Stepanov,
• Igor’ A. Ushakov,
• Alexander V. Vashchenko and
• Olesya A. Shemyakina

Beilstein J. Org. Chem. 2025, 21, 2694–2702, doi:10.3762/bjoc.21.207

• , thioethers, disulfides, phosphonothioates, and trifluoromethyl sulfides. Additionally, due to the presence of two electrophilic sites (the sulfur atom and the carbon of the nitrile function), thiocyanates can readily undergo domino-type intramolecular cyclization reactions to form heterocycles. So, if a

Synthesis of new tetra- and pentacyclic, methylenedioxy- and ethylenedioxy-substituted derivatives of the dibenzo[c,f][1,2]thiazepine ring system

• Gábor Berecz,
• András Dancsó,
• Mária Tóthné Lauritz,
• Loránd Kiss,
• Gyula Simig and
• Balázs Volk

Beilstein J. Org. Chem. 2025, 21, 2645–2656, doi:10.3762/bjoc.21.205

• ; Friedel–Crafts reaction; heterocycles; new ring systems; Introduction In our prior report [1] we disclosed the synthesis of new fused ring derivatives of the dibenzo[c,f][1,2]thiazepine skeleton (1, Figure 1) shown by general structure 2. In recent publications we have also reported the synthesis of new

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

• (intramolecular charge transfer) process. Keywords: fluorescence; hybridization; imidazo[1,2-a]pyridines; Knoevenagel reaction; thiazolidinone; Introduction Heterocycles are compounds of significant interest to organic chemists as drug candidates due to their already widespread presence in many commercially

• scaffolds for several synthetic or natural compounds [5]. Five-membered heterocycles include the thiazolidinone nucleus, characterized by two heteroatoms and a carbonyl group on the fourth carbon, as seen in compounds like rhodanine and thiazolidine-2,4-dione derivatives (Figure 1). These privileged

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

• Studer et al., which belongs to the class of aryl and heteroaryl electrophilic substitutions and is a highly versatile synthetic transformation in traditional organic chemistry. A highly regioselective dual catalytic approach for the novel acylation of electron-rich benzo-fused arenes or heterocycles 15

Pentacyclic aromatic heterocycles from Pd-catalyzed annulation of 1,5-diaryl-1,2,3-triazoles

• Kaylen D. Lathrum,
• Emily M. Hanneken,
• Katelyn R. Grzelak and
• James T. Fletcher

Beilstein J. Org. Chem. 2025, 21, 2524–2534, doi:10.3762/bjoc.21.194

• Kaylen D. Lathrum Emily M. Hanneken Katelyn R. Grzelak James T. Fletcher Department of Chemistry and Biochemistry, Creighton University, 2500 California Avenue, Omaha, NE 68178, USA 10.3762/bjoc.21.194 Abstract A series of pentacyclic aromatic heterocycles representing functionalized

• observed for these annulated molecules, while their analogous non-annulated control compounds were not bioactive. Keywords: annulation; arenes; antimicrobials; fused-ring systems; UV–vis spectroscopy; Introduction Polycyclic aromatic heterocycles are a diverse class of small molecules with utility in a

• , there remains a wide range of chemical space representing these heterocycles that has not yet been explored. Hence, there is an ongoing interest in identifying synthetic strategies to access unreported ring structures and in characterizing the resulting physical and biological properties of such

Palladium-catalyzed regioselective C1-selective nitration of carbazoles

• Vikash Kumar,
• Jyothis Dharaniyedath,
• Aiswarya T P,
• Sk Ariyan,
• Chitrothu Venkatesh and
• Parthasarathy Gandeepan

Beilstein J. Org. Chem. 2025, 21, 2479–2488, doi:10.3762/bjoc.21.190

• developed a regioselective protocol for the direct C1–H nitration of carbazoles, an important class of heterocycles with wide-ranging applications in materials science and natural products chemistry. The transformation proceeds using commercially available Pd2(dba)3 as the catalyst and silver nitrate as the

Ex-situ generation of gaseous nitriles in two-chamber glassware for facile haloacetimidate synthesis

• Nikolai B. Akselvoll,
• Jonas T. Larsen and
• Christian M. Pedersen

Beilstein J. Org. Chem. 2025, 21, 2465–2469, doi:10.3762/bjoc.21.188

• of various trifluoromethyl-containing aza-heterocycles, such as pyridines [2], pyridinones and pyrimidinones [3], tetrazoles [4], tetrazapentalenes [5] and uracil [6]. In addition, it has also been used for the synthesis of fluoro-substituted ketones [7] and substituted trifluoroacetamides via the

• sufficient to be used in a subsequent reaction, hence demonstrating the advantage of using a two-chamber system compared to a one-pot setup, where excess reagents would be present in the crude. As mentioned in the introduction, trifluoroacetonitrile is often used to synthesize a variety of heterocycles via

Transformation of the cyclohexane ring to the cyclopentane fragment of biologically active compounds

• Natalya Akhmetdinova,
• Ilgiz Biktagirov and
• Liliya Kh. Faizullina

Beilstein J. Org. Chem. 2025, 21, 2416–2446, doi:10.3762/bjoc.21.185

• % yield. Jin et al. [85] reported an efficient photoinduced carboborative ring contraction of monounsaturated six-membered carbo- and heterocycles, allowing the regio- and stereoselective synthesis of functionalized cyclopentanes at gram scales. This method leads to the formation of compounds with

Recent advances in Norrish–Yang cyclization and dicarbonyl photoredox reactions for natural product synthesis

• Peng-Xi Luo,
• Jin-Xuan Yang,
• Shao-Min Fu and
• Bo Liu

Beilstein J. Org. Chem. 2025, 21, 2315–2333, doi:10.3762/bjoc.21.177

• congested structures in complex bicyclic systems. 2 Alkaloids 2.1 Lycoplatyrine A In 2020, Sarpong's group disclosed their progress toward a robust and broadly applicable strategy for the C–H functionalization of piperidines and related saturated N-heterocycles. This approach involves lactamization via

• ring, constructing 86 – setting the stage for the group’s key reaction, in which α-hydroxy-β-lactams (e.g., 87) serve as surrogates for α-metalated N-heterocycles in Pd-catalyzed coupling with aryl halides. Both enantiomers of 87 (only one shown in Scheme 10) participated in a Pd-catalyzed

• epimers. This strategy merges photochemical selectivity with cross-coupling efficiency, avoiding reactive metal incompatibility and enabling precise stereocontrol for chiral nitrogen heterocycles. 3 Antibiotics 3.1 Synthetic study toward γ-rubromycin Since 2017, Suzuki's group has developed a