Z-Selective semihydrogenation of alkynes via Ni/Lewis acid synergistic catalyzed system using DMF as hydrogen source and solvent

• Lei Kang,
• Haifeng Gao and
• Luo Yang

Beilstein J. Org. Chem. 2026, 22, 1004–1012, doi:10.3762/bjoc.22.79

• evaluated the influence of the nickel precursor. As summarized in Table 1, the reaction of 1a was performed in DMF (0.8 mL) at 150 °C for 24 h, using various Ni sources (20 mol %) and Co(OAc)2·4H2O (50 mol %). When NiCl₂ was used, 2a (cis-stilbene) was obtained in 68% GC yield (Table 1, entry 1). In

• proceeded to screen various Lewis acids (50 mol %) for the semihydrogenation of diphenylacetylene (1a). The reactions were conducted in DMF at 150 °C for 24 h, and the results are compiled in Table 2. Unsurprisingly, the Lewis acid proved crucial: in its absence, only a 9% GC yield of 2a was obtained (Table

• temperature was also critical. A significant drop in yield was observed at 130 °C (Table 3, entry 18), and although 140 °C provided an 88% yield (entry 19), optimal conversion required 150 °C (entry 2). The reaction time was optimized to 24 hours; shorter (12 h, Table 3, entry 20) or moderately shorter (18 h

Rh(III)-catalyzed chelation-assisted C–H activation/annulation of 2-arylimidazolines with cyclic diazo-1,3-dicarbonyl compounds: a novel approach to tetracyclic annulated derivatives of 2,3-dihydroimidazo[2,1-a]isoquinoline

• Ivan Lyutin,
• Grigory Kantin,
• Olga Bakulina and
• Dmitry Dar'in

Beilstein J. Org. Chem. 2026, 22, 997–1003, doi:10.3762/bjoc.22.78

• obtaining structurally related 5,6-disubstituted 2,3-dihydroimidazo[2,1-a]isoquinolines 4 (Figure 1c) fused with an additional ring via a Rh(III)-catalyzed chelation-assisted C–H activation/annulation with diazo compounds. 2-Arylimidazolines 2 and various substituted cyclic 1,3-dicarbonyl diazo compounds 3

• 2,5,6,7-tetrahydroimidazo[1,2-f]phenanthridin-8(3H)-one 4a (Table 1). The highest isolated yield of 88% was achieved for a reaction conducted in trifluoroethanol (TFE) at 80 °C for 12 h using 2.5 mol % of [RhCp*Cl2]2, (where Cp* = pentamethylcyclopentediene) and 10 mol % of silver triflimide as a

• , as we were unable to find any published successful examples of Rh(III)-catalyzed chelation-assisted C–H activation/annulation with diazo compounds when such heterocyclic substrates were used as CH-components. Substitution at position 4 of the imidazoline ring with a methyl group resulted in the

The role of spacer length and flexibility in peptide self-assembly

• Julian Link,
• Albin Lahu,
• Manfred Wagner,
• Tanja Weil and
• David Y. W. Ng

Beilstein J. Org. Chem. 2026, 22, 986–996, doi:10.3762/bjoc.22.77

• spectrometry (LC–MS) and NMR spectroscopy (Supporting Information File 1, Figures S7–S24). The target tripeptide (ICA) was synthesized in a microwave-assisted peptide synthesizer using the fluorenylmethyloxycarbonyl (Fmoc) solid-phase peptide synthesis strategy [37], synthesizing the peptide from the C- to N

• materials. Experimental Microwave-assisted peptide synthesis Peptides were synthesized using the Fmoc-SPPS strategy [37], synthesizing the peptide from the C- to N-terminus in a microwave-assisted peptide synthesizer on a Fmoc-ʟ-Ala-Clt-resin at scales of 0.10 mmol. Fmoc-ʟ-Ala-Clt-resin (0.10 mmol) was

• deprotection step using a solution of 8% piperidine (DMF, 2.1 mL) for 80 s at 110 °C. The amino acids (0.5 M in DMF, 1.0 mL), DIC (0.75 M in DMF, 1.0 mL) and Oxyma Pure (0.26 M in DMF, 1.5 mL) were added to the resin and the solution was heated to 105 °C for 60 s and held at that temperature for 30 s. The

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

• unsaturated C–C bonds, enabling precise control without molecular hydrogen or stoichiometric reductants. This review summarizes recent advances in iron-, cobalt-, and nickel-catalyzed electroreduction of alkynes and alkenes, highlighting how electrochemical parameters and catalyst design unlock distinct

• ; electroorganic synthesis; reaction mechanism; 3d transition metals; unsaturated C–C bonds; Introduction Reductions of unsaturated C–C bonds Reduction of unsaturated C–C bonds, most notably, alkynes and alkenes, is a synthetic method that has been widely and extensively discussed with a long and rich history

• stereoselective hydrogenation of alkynes under electrochemical and transition-metal-catalyzed conditions. The alkyne semihydrogenation generally benefits from the stronger coordination ability of the C–C triple bonds and the greater accessibility of metal-bound intermediates, thereby often enabling stereocontrol

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

• reduced nitroxides 7a–c (see Supporting Information File 1) confirmed the 7,7,9-triethyl-1,4-dioxa-8-azaspiro[4.5]decane core and revealed distinct alkynyl signatures: a singlet at 3.29 ppm (1H) for 7a, a singlet at 4.28 ppm (2H) for 7b, and two singlets at 3.89 ppm (2H) and 1.46 ppm (9H) for 7c. For the

• bonds afforded the corresponding saturated derivatives 8a–d. Specifically, alkynyl derivatives 7a–c were hydrogenated with H2 over a palladium catalyst, while the allyl derivative 7d was reduced with hydrazine over Raney nickel (Scheme 4). The absence of signals corresponding to alkene protons in the 1H

• spectrum of the nitroxide 9a (TEEPONE) was identical to that reported in the literature [21], and the IR spectrum of 9d was similar, with a strong absorption band at 1716 cm−1, characteristic of the carbonyl (C=O) stretching vibrations. The 1H NMR spectra of the reduced derivatives of 9a,d showed no

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

• pharmaceuticals and functional materials, making efficient C–N bond formation a fundamental transformation in synthetic chemistry. The direct hydroamination of alkenes using (hetero)aromatic N–H nucleophiles offers an atom- and step-economical strategy; however, the reduced nucleophilicity and distinct

• , 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

• remains a primary objective of modern organic synthesis [5][6]. Among the diverse strategies available for C–N bond formation, the direct addition of an N–H bond across a C–C double bond, known as hydroamination, is an ideal transformation considering atom and step economy [7][8][9][10][11][12

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

• 1a–c were treated with 2.5 equiv of n-BuLi in anhydrous THF at −78 °C under a nitrogen atmosphere to generate the corresponding aryllithium intermediates, followed by introduction of CO2 via a balloon. The reaction mixture was then allowed to warm to room temperature and stirred overnight to ensure

• complete trapping of the aryllithium intermediates by CO2. After aqueous quenching and extraction, the crude products were directly subjected to HPLC analysis. To evaluate the generality of this strategy, three brominated SiR precursors 1a–c, all accessible by reported procedures, were selected as model

• ethyl acetate and concentrated before being directly subjected to amide coupling without chromatographic purification. To demonstrate the utility of this strategy for probe construction, we selected three representative SiR scaffolds 1a–c, which were widely used in super-resolution imaging, for direct

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

• University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan 10.3762/bjoc.22.71 Abstract A novel benzocyclization protocol has been developed for the synthesis of quinoline-fused lactams by palladium-catalyzed sequential C–H/N–H functionalization of quinoline-2-carboxamides and 1,2-dihaloarenes. The reaction

• proceeds at the C–H bond on the quinoline adjacent to the amide group and at the amide N–H bond in the presence of 10 mol % Pd(OAc)2 in o-xylene as a solvent to afford the cyclized product in 34% yield. The yield increases to 81% when the reaction is carried out with 80 mol % P(4-MeOC6H4)3 as a ligand and

• corresponding heterocycle-fused compounds. The high chemoselectivity of the 1,2-dihaloarene functional groups is confirmed in this reaction, thus enabling divergent synthesis of various multifused heterocyclic systems. Keywords: C–H activation; chemodivergent synthesis; C–N coupling; fused-ring system

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

• with aromatic aldehydes does not result in the formation of an azirinyl-substituted β-hydroxy-α-diazocarbonyl compound, but is accompanied by a tandem intramolecular cyclization involving the hydroxy group and the C=N bond of the azirine to form a bicyclic intermediate, a 4-diazo-2-oxa-7-azabicyclo

• reaction of 2-(diazoacetyl)-2H-azirines 1 with aromatic aldehydes 2, which does not terminate in condensation to form an azirinyl-substituted β-hydroxy-α-diazocarbonyl compound 3, but is accompanied by a tandem intramolecular cyclization involving the hydroxy group and the azirine C=N bond to form a

• MeCN) for the reaction of azirine 1a and benzaldehyde (2c, Scheme 3). Calculations indicate that condensation and subsequent cyclization should readily occur at room temperature, with only the diastereoisomer (1RR,3SR,6RR)-Phe-C (with the Ph group from benzaldehyde in the equatorial position

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

• enhance the formation of transition state B. The highly diastereomic ratio of 6a in syn-form may be generated from transition state B. The formation of intermediate C is the rate-limiting step. When intermediate C is formed, the protonation happened rapidly to afford 6a in high enantioselectivity. The

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

• their stereoselective reactions remains challenging. Here, we examine the diastereoselective generation and trapping of α-boryl lithium species formed by ring opening of substituted iodomethylcyclopropanes. After lithium–iodine exchange and selective C–C bond cleavage, these intermediates react with a

• delocalization leads to the formation of a partial π C–B bond (Scheme 1) [1][2], which provides a unique stabilization to the carbanionic center and affects its reactivity towards electrophiles. In recent years, α-boryl carbanions have attracted significant attention as highly versatile intermediates capable of

• engaging in diverse bond-forming processes, including C–C, C–O and C–N bond formations [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. Despite their growing utility, controlling the stereoselectivity in substitution reactions of α-boryl carbanions remains a formidable

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

• of proteins are linear polypeptide chains, possessing a single N- and C-terminus and hence presenting these regions as attractive targets for site-specific modification. Indeed, over 80% of protein termini are solvent-exposed and chemically accessible [5]. Notably, the N-terminal amine and C-terminal

• cysteine [15]. These intermediates enable downstream chemical conjugations such as Pictet–Spengler condensation [16][17][18] and Horner–Wadsworth–Emmons (HWE) olefination [19] (Scheme 2c). With respect to C-terminal modification, one of the earliest strategies involved the use of intein-mediated protein

• splicing to generate a C-terminal thioester from recombinantly expressed proteins [20][21][22]. One distinctive feature of the C-terminal carboxylate is its lower oxidation potential compared to the side chains of aspartate or glutamate, making it more amenable to selective redox-based modifications. 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

• . This effect is probably more dominant in gold chemistry than in most other transition-metal complexes; it can on occasions appear even more important than the formal oxidation state and d-electron count. Tilset and co-workers have recently summarised the importance of the trans-influence in C^N

• electron-rich trialkylphosphines, increased the proportion of N-bonded thiocyanate [24]. More recently, Espinet and co-workers used solution microcalorimetry with in-situ generated HI to provide bond dissociation energy scales for the Au–C bonds in R–Au(PPh3) (R = Me, aryl or alkynyl), and further to

• determine the effect of ligands L in the protolysis of LAuPh, where reaction enthalpies were shown to decrease in the order P(OPh)3 > PPh3 ≈ PMe3 > IPr > PCy3 (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene). Depending on L these protolysis enthalpies with HI span a range of 50 kJ/mol. The Au–C

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

• distances range from 1.512 to 1.532 Å, which in most compounds except 4a is longer than the average sulfoxide bond length of 1.489–1.515 Å [45][46] and close to the bond length in DMSO [47]. The S–C(cat) bond distances range in the narrow range of values 1.782–1.789 Å. The S–C(R) distance varies in the

• range of 1.838–1.892 Å. If the C(R) atom is aromatic as in the case of 7a, the average S–C distance has a tendency to be slightly shorter (1.804 Å) due to a possibility of weak conjugation of the π-system in the aromatic ring with the S=O double bond, but nevertheless close to the corresponding value

• for 6a. The O–S–C(cat) and O–S–C(R) bond angles vary in the ranges of 104.2(2)–106.75(7)° and 103.6(3)–110.0(3)°, respectively. The torsion angle (C(R)–S–C(cat)–C(OH)) between the plane of the aromatic ring of the catechol fragment and the hydrocarbon group at the sulfur atom ranges from 66.7° to 84.3

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

• approaches [2][3][4][5]. In this context, comprehensive medicinal chemistry studies consistently highlight the prominence of isatin-derived frameworks among bioactive and anticancer agents [6]. The remarkable reactivity of the isatin scaffold arises from its dual functionality, combining an electrophilic C-3

• aromatic pattern of the isatin core. The IR spectrum showed a strong imine C=N band at 1610 cm−1, and the absence of the C-3 carbonyl stretching band confirmed complete condensation. The 13C NMR spectrum revealed multiple sets of closely related signals, consistent with the presence of three C=N

• 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

• products in acidic media subjecting the condensation products 3b and 4b to heating in glacial acetic acid at 50 °C for 6 hours revealing that compound 3b was stable whereas compound 4b decomposed into the starting reagents (see the TLC data in Supporting Information File 1, Figure S3). Apparently, after

• additionally due to C–H···π intramolecular interactions: φ1 = 106.8(2)° (N3–C13–C12–C5) and φ2 = 99.6(2)° (N4–C18–C12–C5) (Figure 2a). The molecules of 4,5-DPDAF are packed into stacks due to π-stacking interactions between diazafluorenes which are stabilized by C–H···N interactions between pyridine and

• diazafluorene fragments along (a + b) (Figure 2b). The stacks of molecules are linked together via π···π and C–H···π interactions between pyridine fragments (Figure 2c). To further evaluate the complexation behavior of 4,5-DPDAF we co-crystallized the compound with ZnCl2 resulting in a unique complex (Zn–4,5

Synthetic study of vic-bromination of diarylacetylenes, easy purification and separation

• Akane Togo,
• Hiyono Suzuki,
• Yuto Akai,
• Makoto Matsumoto,
• Yoshinori Suzuma,
• Hidehiko Kodama and
• Kouichi Matsumoto

Beilstein J. Org. Chem. 2026, 22, 795–802, doi:10.3762/bjoc.22.61

• isomers are formed together might be due to the equilibrium between A and C, although there are many unknown points. Conclusion In summary, we have developed a simple and selective procedure of the synthesis of (E)-1,2-dibromo-1,2-diphenylethylene from diphenylacetylene by using NBS and FeBr3 in CH2Cl2

• ; HRMS (ESI) m/z: [M + Na]+ calcd for C14H11Br2, 336.9222; found, 336.9215. Selected and previous reports for bromination of diphenylacetylenes (a–c), and this work (d). Gram-scale synthesis of (a), and control experiments of (b), (c) and (d). n.r. = no reaction. Plausible reaction mechanism of the

• ., Ltd. for various supports in this work. Finally, we wish to express our acknowledgments for Kindai University Joint Research Center for use of facilities. Funding This work was financially supported in part by JSPS KAKENHI (JP24K08506) (Grant-in-Aid for Scientific Research [C]) and 2025 Kindai

Halogenated azobenzene acrylates: from efficient solution photoswitching to stable solid-state photochromic materials

• Martina Vachtlová,
• Michaela Fecková,
• Vítězslav Zima,
• Jan Podlesný,
• Milan Klikar,
• Oldřich Pytela,
• Patrik Pařík,
• Jakub Opršal,
• Eliška Juhaňáková,
• Veronika Chrtová and
• Filip Bureš

Beilstein J. Org. Chem. 2026, 22, 782–794, doi:10.3762/bjoc.22.60

• arrangement. Kinetics studies identified the most stable Z-isomer of the difluoro derivative (τ1/2 = 3.74/6.59 h at 60 °C in DCE/CDCl3). The monofluoro derivative embedded in a polystyrene film demonstrated photoresponsive behavior and remarkable stability by maintaining a macroscopically visible color change

• viscous liquids or slowly solidified powders, due to the long aliphatic polymerizable pendant, which significantly suppresses facile crystallization. Hence, the target molecules were obtained as semi-crystalline solids undergoing a melting process (1a–c) or as viscous liquids (1d–f) where only a glass

• normal conditions (20 °C, 101.325 kPa) with a Tg = −49 °C, monochloro analogue 1c is a crystalline solid with Tm = 33 °C. From this perspective, the chlorine atom is at the size boundary, thus the number of appended chlorine atoms most likely determines the degree of supramolecular organization, as

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

• afford triazoles IXa,c,d or, in case of product IXb with (R)-alanine methyl ester. The absolute stereochemistry of IXb is R. All compounds with defined absolute configuration described below were synthesized from IXb, thereby preserving the absolute stereochemistry and affording the corresponding R

• enantiomer. The synthetic routes of compounds Z1–15 are shown in Scheme 6. First, intermediates 2 and 3 were reacted under basic conditions in MeCN to obtain intermediate 4 which was subsequently reacted with bromides IXa–c to get compounds Z1–3 in 80–91% yield. Then, compounds Z1–3 were treated with with

• dioxaborolane 7 or boronic acid 9 and IXa–c. Next, Z16–18 and Z23–25 were obtained by Williamson ether synthesis from the intermediates 8, 10 and isoxazole intermediates 2. Finally, hydrolysis in the presence of LiOH and reduction in the presence of lithium aluminum hydride provided target compounds Z19–22 and

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

• oxidation conditions, reaction in the presence of DMSO and NaHCO3 under conventional or microwave heating to ≈100 °C, were applied to the bromides derived from these alcohols by treatment with PBr3, resulting in the desired aldehydes which successfully underwent reductive amination reactions with 2

• ester 13b into the corresponding amide using AlCl3 were not promising and therefore the hydrolysis of this ester to corresponding carboxylic acid 14 was tested. Using KOH in MeOH at 35–40 °C for the ester hydrolysis reaction resulted in decarboxylated compound 12b being isolated as the sole product in

• ester being recovered. Thus, for the preparation of the aldehydes we opted for reduction of the esters 13a–d and 13f to their corresponding alcohol derivatives (17) followed by oxidation to the aldehyde. Esters 13a–c were readily converted into the corresponding alcohols 17a–c in excellent yields of 92

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

• characterization of new brassinosteroid (BR) analogs, in which substituents with different electronegativities and molecular sizes have been attached to a C-22 benzoate function, are described. The biological activities of all new compounds were evaluated by using the rice lamina inclination test (RLIT) and

• inhibition of root growth of Arabidopsis thaliana. The RLIT data is compared with those previously reported for two series of compounds having the same substitution pattern at C-22 but different structure in ring A. This comparison revealed that a 2α,3α-dihydroxy configuration is more active than a 3

• matter of current interest. For example, derivatives of teasterone (3), compounds 4–11, and castasterone, compounds 12–14, with benzoyl function at C-22 (Figure 2) have been synthesized, and their bioactivities have been evaluated by BSIB, RLIT, and inhibition of root and hypocotyl elongation in A

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

• structure somewhat rotated out of planarity (dihedral angles between aromatic C–C and vinylic CH are 34°). This presumably still allows for some conjugative stabilization from the aromatic rings to the enone π-systems and reduces eclipsing interactions between the ortho-methyl groups and the vinylic H

• demonstrates the general viability of sulfinate addition to produce C-tertiary sulfones, but also implies steric limits to these processes in double intermolecular conjugate addition with Rongalite as the nucleophile. Our approach was to use competition experiments to indicate the relative reactivity of

• methanesulfinate or p-toluenesulfinate and 1 equivalent of Rongalite (50 °C, AcOH/H2O, o/n) led to a mixture of products. These results are tabulated in Table 1. Mixtures of cyclic and acyclic products were obtained in both cases. Our initial interpretation was that the ratios reflected the relative rates of

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

• heating were used. Notably, this process can proceed solvent-free at 140 °C, which is suitable for less reactive substrates. Various exo-cyclic alkenes obtained from cyclic (hetero)aliphatic ketones such as cyclobutanone, azetidinone, thienone, as well as endo-(hetero)cyclic alkenes containing oxygen

• 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

• -nitro-1,2-diphenylcyclopropene 127 in primary, secondary, and tertiary alcohols, as well as using certain thiols. The authors suggest that the reactions proceed via a stage of heterolytic cleavage of the C–N bond of the starting 3-nitro-1,2-diphenylcyclopropene to form a cyclopropenyl cation, which then

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

• were recorded at 25 °C on a Bruker AVANCE III HD 500 or HDX 800 MHz NMR spectrometer equipped with a cryoprobe. The 1H and 13C chemical shifts were referenced to solvent peaks for CDCl3 at δH 7.26 and δC 77.2, respectively. UHPLC–LRESIMS analysis was performed using a previously reported method [32

• detailed below. The previously described plant compounds salicifoliol (1) [15][16] and (+)-pinoresinol (2) [17] were identified following 1D and 2D NMR (1H, 13C, COSY, HSQC, HMBC, and ROESY), [α]D, MS data analysis, and comparison with literature values. (+)-Salicifoliol (1): clear gum; [α]D25 +36.4 (c

• 0.09, MeOH); lit. [α]D25 +56.3 (c 0.06, MeOH) [33]; see Supporting Information File 1 for 1H and 13C NMR data in CDCl3; LRESIMS m/z: [M + H]+ 251, [M − H]− 249. (+)-Pinoresinol (2): brown gum; [α]D25 +55.5 (c 0.07, MeOH); lit. [α]D25 +20.0 (c 0.75, MeOH) [34]; UV–vis (MeOH) λmax (log ε) 230 (3.94), 279

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

• (TBHP, 0.6 equiv), which was added at 0 °C in three portions, affording 13-hydroxycasbene (8) as a single diastereomer in 48% isolated yield at milligram scale. The reaction could be performed on a gram scale albeit with a diminished isolated yield (39%, 79% brsm). We thought that with the most reactive

• -cryptomeridiol (3). Synthesis of depressin (1), cryptomeridiol (2), and 4-epi-cryptomeridiol (3). a) Synthetic route of 1 starting from casbene (4). b) Preparation of 2,4-nitrophenylhydrazone derivative of 13-ketocasbene (9) for X-ray diffraction. c) Synthetic route of 2 and 3 starting from germacrene A (5