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

• metal–alkenyl intermediate. In some cases, this organometallic species can further undergo chain walking, where iterative β-hydride elimination and reinsertion enable migration of the metal center along the carbon skeleton before product release, thereby allowing remote hydrogenation or positional

• through the combination of anodic iron salts and electrochemically generated silyl hydrides, actively participate in the reaction pathway (Scheme 2C) [91]. The authors proposed that the ring-opening product arises from β-carbon elimination of an intermediate generated via migratory insertion, followed by

• chemoselectivity that are difficult to achieve under classical HAT conditions. Substrates featuring a quaternary carbon adjacent to the alkyne exhibited diminished E/Z selectivity, which was tentatively attributed to increased steric hindrance surrounding the putative cobalt–alkene intermediate. Interestingly

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

• subsequent reaction with moderately basic organometallic reagents, such as 2-alkynyl- and 2-allylmagnesium halides, enables the facile introduction of diverse substituents, including those with functional groups. If necessary, the multiple carbon–carbon bonds in the side chain can be subjected to

• alkynyl- or allylmagnesium halides gave 2-alkynyl or 2-allyl-substituted nitroxides. Finally, carbon–carbon multiple bonds were removed via Pd-catalyzed hydrogenation and the nitroxide group was recovered by mild oxidation. This approach was used to prepare both symmetric 2,2,6,6-tetraethyl- and 2,2,6,6

• allyl derivative 7d, extensive signal overlap prevented rigorous simulation, but characteristic terminal vinyl protons at 5.83, 5.28, 5.27 ppm were clearly observed. Elemental analysis and HRMS data were in agreement with the proposed structures. Subsequent hydrogenation of the unsaturated carbon–carbon

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

• the direct hydroamination of alkenes using aromatic amines and aza-heterocyclic N–H nucleophiles under copper catalysis. The primary focus is on the mechanistic paradigms, Cu–amido pathways, Lewis acid activation, and carbon-radical manifolds, and on how these distinct activation modes translate into

• Michael acceptor. This coordination increased the electrophilicity of the β-carbon, facilitating nucleophilic attack. The reaction proceeded efficiently with various activated olefins 14, affording N-substituted products 15 in high yields with good regioselectivities. Notably, the catalytic role of copper

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

• metal affinity [9][10]. It is therefore expected that annulation of the amide moiety in quinoline-2-carboxamides would extend their functionality as biologically active structures, ligands, and extractants. Transition-metal-catalyzed coupling reactions are crucial for constructing carbon–carbon and

• carbon–heteroatom bonds. The classical coupling reactions, such as Kumada–Tamao–Corriu coupling [11][12][13], Sonogashira coupling [14][15], Negishi coupling [16][17], Migita–Kosugi–Stille coupling [18][19][20], Suzuki–Miyaura coupling [21][22], and Hiyama coupling [23][24] involve carbon–halogen and

• carbon–metal species (Scheme 1a). Fagnou and co-workers reported direct arylation reactions with palladium(II) acetate to synthesize biaryl compounds via concerted metalation–deprotonation (CMD; Scheme 1b) [25][26][27]. Buchwald, Hartwig, and co-workers explored carbon–nitrogen coupling reactions that

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

• -conformation and the absolute configurations of 7d’ was unambiguously assigned as 2S and 3S, this means that the benzophenone-imine group and bromophenoxymethyl group should be arranged on the same side of the longest carbon chain to be syn before lactamization, therefore, the absolute configuration of 6d’ was

Diastereodivergent electrophilic trapping of α-boryl lithium derivatives

• Tereza Pavlíčková,
• Noam Orbach and
• Ilan Marek

Beilstein J. Org. Chem. 2026, 22, 882–887, doi:10.3762/bjoc.22.68

• ; Introduction α-Boryl carbanions 1 (Scheme 1), also referred to as boron alkylidenes or borata alkenes, represent a fascinating class of organoboron intermediates characterized by the delocalization of electron density from the negatively charged carbon center toward the electron-deficient boron atom. This

The trans-influence in gold chemistry from a catalytic perspective

• Manfred Bochmann

Beilstein J. Org. Chem. 2026, 22, 838–856, doi:10.3762/bjoc.22.66

• trialkylphosphines, anionic carbon and hydride ligands. N- and O-lone pair donors (pyridine, water) are weak ligands. The following indicative series is typical for Pt(II), although there may be slight variations in the specific ordering depending on the complex type under investigation: CO, CN−, C2H4 > P(alkyl)3

• , while C^N^C and C^C^N ligand frameworks look like simple structural isomers, their reactivity and analysis of their bonding has shown that replacing the weak N(pyridine) donor by strongly donating anionic carbon leads to profound changes in gold orbital ordering, often with drastic consequences for

• chemical shifts [32][49][50][51][52]. Both neutral and cationic gold(III) hydride pincer complexes could be prepared. They fall into two categories: those of types 8–11 where the hydride ligand is trans to an N donor (shielding, negative δ shifts), and those where the hydride is trans to an anionic carbon

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

• the sulfoxides, the signals of the carbon atoms bearing the OH groups are shifted downfield and appear at δ 148.4–150.0 ppm. The sulfinyl group also influences the signals of aliphatic carbon atoms. For example, in sulfoxide 1a, the signal of the secondary carbon in the isopropyl substituent is

• shifted downfield (δ 54.4 ppm) compared to the analogous carbon atom in thioether 1 (δ 41.9 ppm). These results indicate a pronounced electron-withdrawing effect of the sulfinyl group, as well as the presence of strong intra- and intermolecular O–H···O=S bonds, which is consistent with the IR

• supported by the oxidation potential data. As the number of carbon atoms in the aliphatic hydrocarbon substituents of sulfoxides increases, their activity in the DPPH test diminishes. Compounds 7 and 7a, which contain a naphthyl substituent, exhibit the highest IC50 values among the studied catechols

Total synthesis of the capsular polysaccharide repeating unit towards the development of a glycoconjugate vaccine against Klebsiella pneumoniae ST512

• Shuo Zhang,
• Ondřej Daněk and
• Peter H. Seeberger

Beilstein J. Org. Chem. 2026, 22, 821–827, doi:10.3762/bjoc.22.64

• followed by catalytic hydrogenation over palladium on carbon, affording disaccharide 21 in 47% yield over two steps. Similarly, trisaccharide 22, tetrasaccharide 23, and pentasaccharide 24 were prepared from intermediates 14, 15, and 17, respectively. The analogues 21–24, together with the repeating unit

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

• retained the four-signal pattern of isatin (H4', H5', H6', H7'), slightly shifted by the new structural environment. In the 13C NMR spectrum, the amide carbonyl appeared at δ 176.5 ppm, while a key quaternary carbon at δ 61.0 ppm (C3‘) – formerly the C-3 isatin carbonyl carbon – confirmed the formation of

Knoevenagel condensation of 4,5- and 1,8-diazafluorenes

• Darya S. Cheshkina,
• Christina S. Becker,
• Alina A. Sonina and
• Maxim S. Kazantsev

Beilstein J. Org. Chem. 2026, 22, 803–812, doi:10.3762/bjoc.22.62

• to the iminium cation occurs via the methylene carbon of the corresponding enamine tautomeric form 1B or 2B. Thus, this process is limited by the concentration of this form which is expected to be higher for 1,8-diazafluorene (2) due to the activation by the neighboring nitrogen atoms via the

Preparation of 3-(alkylamino)imidazo[1,2-a]pyridine-2-carbaldehydes via Kornblum oxidation and unexpected ring-opening reactions of the corresponding alcohols under oxidative conditions

• Sandile J. Mkhize,
• Memory Zimuwandeyi,
• Manuel A. Fernandes,
• Amanda L. Rousseau and
• Moira L. Bode

Beilstein J. Org. Chem. 2026, 22, 763–770, doi:10.3762/bjoc.22.58

• similar reactions on alcohols 17b–d led to the corresponding ring-opened products 18b–d (Scheme 4). The ring-opened products were isolated in yields of 26–36%, with loss of one carbon atom occurring (-CH2OH). To test whether C-2 decarboxylation could have immediately preceded ring-opening, decarboxylated

• mechanism. Oxidative ring-opening of imidazo[1,2-a]pyridines has been reported previously, but in these cases different ring-opened products were identified. These previous results are compared to our present report in Figure 5. Wang and co-workers [30] reported ring-opening accompanied by loss of a carbon

• , rt, 20–24 h. Ester hydrolysis and in situ decarboxylation. Ester reduction to the corresponding alcohols. Reaction yields are provided in parentheses. Oxidative ring-opening with loss of one carbon atom. Yields are provided in parentheses. Oxidative conditions applied to decarboxylated compound 12b

Synthesis and biological evaluation of new brassinosteroid analogs with C-22 benzoate function

• María Núñez,
• Camila Escobar,
• Mario Párraga,
• Mauricio Soto,
• Luis Espinoza-Catalán,
• Katy Díaz and
• Andrés F. Olea

Beilstein J. Org. Chem. 2026, 22, 753–762, doi:10.3762/bjoc.22.57

• 7.2 Hz, H-22b), are assigned to carbinolic hydrogens H-22a and H-22b, respectively. In the 13C NMR spectrum, the signals observed at δ = 166.57, 143.31, 129.40, 128.93, 127.65, and 21.52 ppm, are assigned to carbon ArCOO, C-4’, C-2’, C-3’, C-1’, and CH3-Ar of the benzoate group, respectively. All

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

• dipolarophile can lead to a change in the mechanism and to an effective electrophilicity polarization toward the terminal carbon atom. This finding strongly supports the suitability of moderately activated olefins as dipolarophiles for the catalyzed asymmetric cycloaddition reactions involving azomethine ylides

• reactions proceed with high stereoselectivity, providing products with eleven chiral carbon atoms in three steps. In 2018, Zhang and co-workers presented a sequential process based on a combination of inter- and intramolecular (3 + 2) cycloaddition reactions to prepare highly fused heterocyclic systems

• due to the possibility of cycloaddition at the carbon–oxygen double bond (C=O) of the aldehyde, which acts as an alternative to the carbon–carbon double bond (C=C) [83]. In 2016, Sridharan reported a one-pot iridium-catalyzed three-component dehydrogenation/1,3-dipolar cycloaddition cascade reaction

Anti-invasive and cytotoxic evaluation of a (+)-pinoresinol-based semisynthetic library against glioblastoma

• Chen Zhang,
• Kah Yean Lum,
• Jonathan M. White,
• Paul I. Forster,
• Nicholas Booth,
• Sunita A. Ramesh and
• Rohan A. Davis

Beilstein J. Org. Chem. 2026, 22, 691–704, doi:10.3762/bjoc.22.54

• 7.06 (2H), 6.83 (2H)), as well as two methine (δH 4.75 (2H), 3.11 (2H)), one methylene (δH 4.27/3.90, 4H), and one methoxy signal (δH 3.92, 6H)). The 13C NMR and HSQC spectra of 5 indicated a total of 10 unique carbon signals, including one methoxy (δC 56.6, 2C), two methine (δC 85.4, 53.9, 4C), one

• methylene (δC 71.8, 2C), and six aromatic carbon signals (δC 147.6, 142.9, 133.3, 122.3, 108.4, 108.0, 12C). Comparison of the 1H and 13C NMR data of 5 and (+)-pinoresinol (2) showed a high degree of homology, with the major differences in NMR data associated with a chemical shift of the aryl resonances

• collected on a Rigaku XtaLAB synergy diffractometer using Cu Kα radiation at 100.0(1) K using an Oxford Cryostream cooling device. The structure was solved by direct methods and difference Fourier synthesis [36]. Hydrogen atoms bound to the carbon atom were placed at their idealized positions and included

Synthesis of depressin, cryptomeridiol and 4-epi-cryptomeridiol enabled by a terpenoid chiral pool-producing platform

• Yao Kong,
• Tao Wang,
• Chen Wang,
• Pengcheng Zhang,
• Yuanning Liu,
• Kaibiao Wang,
• Fen Liu,
• Hongli Jia and
• Zhengren Xu

Beilstein J. Org. Chem. 2026, 22, 683–690, doi:10.3762/bjoc.22.53

• cyclases; Introduction Terpenoids are one of the most important family of natural products that have been found to be produced in all domains of life. Although containing only carbon, hydrogen and oxygen atoms in most cases, over 100,000 terpenoid structures containing diverse skeletons and rich oxidative

• pathway, have been adopted to provide the two key five-carbon building blocks DMAPP and IPP. With the recent advancement in the field of synthetic biology, more chiral terpenes (e.g., guaia-6,10(14)-diene [7][8], drimenol [9][10], and ent-atiserenoic acid [11] as shown in Figure 1b) became easily

• -carbon alcohols prenol and isoprenol. Late-stage redox modification of the casbene skeleton allowed us to synthesize depressin in nine steps, while transannular cyclization of the germacrene A skeleton followed by hydration has made cryptomeridiol and 4-epi-cryptomeridiol easily accessible in two steps

Advantages of PROTACs in achieving selective degradation of homologous protein families

• Luxi Yang,
• Xinfei Mao,
• Jingyi Zhang,
• Jing Shu,
• Wenhai Huang,
• Xiaowu Dong,
• Yinqiao Chen and
• Mingfei Wu

Beilstein J. Org. Chem. 2026, 22, 628–661, doi:10.3762/bjoc.22.49

• pharmaceutical chemists. In 2019, Gray, Zhang and co-workers designed a PROTAC-1 (1) to degrade CDK4/6 [21]. To construct compound 1 they used the CDK4/6 inhibitor palbociclib as the POI ligand, pomalidomide, which combines with CRBN as the E3 ligand and a 4-carbon alkyl linker to connect them. The compound can

• C5-linker series (Figure 7). As for these compounds, the difference is the number of carbon atoms (n) between nexturastat A and the triazole fragment or the number of carbon atoms (m) between pomalidomide and the triazole fragment. It was found that compound 20d (DC50 = 1.64 ± 0.24 nM) with a medium

• , the resulting PROTAC showed a robust selective degradation of p38δ. Compound 33 degraded p38δ with a DC50 of 46.17 ± 9.85 nM and Dmax of 99.41 ± 3.31% but did not degrade α, β, or γ at all. In some cases, even changing single carbon atoms of the linker segment may cause a surprising change in the

Computational prediction of C–H hydricities and their use in predicting the regioselectivity of electron-rich C–H functionalisation reactions

• Rasmus M. Borup,
• Nicolai Ree and
• Jan H. Jensen

Beilstein J. Org. Chem. 2026, 22, 603–610, doi:10.3762/bjoc.22.46

• primarily anthracene derivatives and benzyl C–H bonds, suggesting potential systematic errors in QM computations or experimental measurements. Radical and cation stabilities generally follow the trend: tertiary > secondary > primary methyl carbon stability. Our study also explores the correlation between

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

• regioselectivity (Figure 4). In the protonated intermediate 12 derived from epoxide 9a, the carbon atom preferentially attacked by chloride bears a relatively more positive charge, which is consistent with an electronically favoured nucleophilic attack. In contrast, for the protonated intermediate 15 derived from

• epoxide 9b, the more positively charged epoxide carbon is sterically shielded by the neighbouring ester carbonyl group. As a result, nucleophilic attack occurs at the sterically more accessible, albeit less positively charged, epoxide carbon. These observations indicate that the regioselectivity of

Melifoliox B, a novel phloroglucin derivative isolated from Melicope barbigera (Rutaceae) and synthesis of new oxidation products from melifoliones A and B

• Horst Weber,
• Kim-Thao Tran-Cong,
• Bernhard Mayer,
• Guido J. Reiss,
• Iryna S. Konovalova,
• Marc S. Appelhans,
• Kenneth R. Wood and
• Claus M. Passreiter

Beilstein J. Org. Chem. 2026, 22, 535–546, doi:10.3762/bjoc.22.39

• careful analysis of the 2D NMR spectra (HSQC, HMBC) all carbon signals of both isomers could be unambiguously assigned to the corresponding atoms (Table 2). This clearly shows that the data given in literature [4] must be corrected. Oxidation of melifoliones Mixtures of melifolione A (1) and melifolione B

Synthesis and uranyl(VI) extraction performance of a calix[4]pyrrole–tetrahydroxamic acid receptor

• Sara Karnib,
• Rana Baydoun,
• Wissam Zaidan,
• Nancy AlHaddad,
• Omar El Samad,
• Bilal Nsouli,
• Francine Cazier-Dennin and
• Pierre-Edouard Danjou

Beilstein J. Org. Chem. 2026, 22, 486–494, doi:10.3762/bjoc.22.36

• their 2,5-positions through sp3-hybridized meso-carbon atoms [10]. The ability of CPs to selectively bind anions [11], cations, ion pairs and neutral guest species, combined with the versatility to introduce diverse functional groups, has enabled the fabrication of calix[4]pyrrole-based supramolecular

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

• active site [17]. Hence, we decided to functionalize this position with an alkyl linker consisting of 9 carbon atoms to mitigate any steric clashes between the HDAC inhibitor and the nanogold particle, which could be detrimental to the probe binding affinity (Figure 1). Further to this, we previously

• clearly visualized in association with the CoREST complex by cryo-EM; however, its absence in side-view 2D classes prevented precise localization of the HDAC catalytic domain. We speculate that the flexibility of the 9-carbon alkyl linker, and additional flexible linker to the nanogold particles, may have

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

• reference to 13C NMR signals of the starting material 12, the 13C NMR spectrum of compound 7 exhibits four additional aromatic carbon resonances, which are consistent with the phenyl ring carbons of phenyl selanyl function tethered to the naphthalimide core. The signal at 142 ppm is assigned to the ipso

• carbon directly attached to the selenium atom. The resonance observed at 136 ppm corresponds to the chemically equivalent ortho carbons. The meta carbons appear as a single signal at 130 ppm, while the para carbon is observed at 127 ppm. The reduced number of aromatic signals arises from the chemical

• equivalence of the ortho and meta carbon pairs, confirming the proposed structure. In contrast, with reference to the 13C NMR signals of starting material 12, compound 8 exhibited eight new 13C NMR peaks in the aliphatic region (14–32 ppm), which is attributed to the incorporation of an octyl selenide unit

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

• %) with the calculated values. The carbon and hydrogen contents were determined using the Pregl gravimetric method, nitrogen by using Dumas' gasometric micromethod, and chlorine by the mercurimetric method. N-Methyl-ᴅ-glucamine and (−)-cytisine ((1R,5S)-1,2,3,4,5,6-hexahydro-1,5-methano-8H-pyrido[1,2-a

Non-central chirality in organic chemistry

• Ken Tanaka and
• Naohiko Yoshikai

Beilstein J. Org. Chem. 2026, 22, 370–371, doi:10.3762/bjoc.22.24

• ; chiroptical properties; molecular chirality; Chirality is a foundational concept in organic chemistry, traditionally framed around tetrahedral carbon stereocenters. Over the past decades, however, it has become increasingly clear that molecular handedness is not confined to localized points in space. Axes