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

• process relies on the rapid interconversion of the enantiomers in the racemic substrate, which in turn relies on the acid-promoted isomerization between the aromatic indole and the nonaromatic exocyclic enamine intermediate. Very recently, Chen and co-workers reported that using a Mn catalyst with

• 81 was prepared via a Polonovski–Polish reaction and isomerization, which, when adopting the proper conformation, spontaneously underwent an intramolecular [4 + 2] cycloaddition to construct the unsaturated bridged ring of (±)-keramaphidin B in a single transformation. Subsequently, the iminium ion

• protonation during reduction or an isomerization event. Kinetic translocation of the double bond to the correct position enabled an intramolecular Heck reaction, a transformation originally developed by Fukuyama (Scheme 12) [78]. Hydrogenation of (−)-tabersonine to (−)-decahydrotabersonine by Catherine

Reactivity umpolung of the cycloheptatriene core in hexa(methoxycarbonyl)cycloheptatriene

• Dmitry N. Platonov,
• Alexander Yu. Belyy,
• Rinat F. Salikov,
• Kirill S. Erokhin and
• Yury V. Tomilov

Beilstein J. Org. Chem. 2026, 22, 64–70, doi:10.3762/bjoc.22.2

• isomerization. However, these isomerizations are known to proceed as 1,5-sigmatropic shift [32] as observed in the formation of compounds 8 and 9, whereas the formation of products 4 through this pathway would require at least two consequent shifts. Thus, the absence of any intermediate-shift products along

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

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

• having electron-withdrawing groups at the triple bond can easily undergo prototropic isomerization to form corresponding unstable allene structures, particularly in acidic conditions. When N-n-Bu CF3-iminopropargyl alcohol 1h was introduced to the reaction, product 2h was obtained in a slightly lower

Recent advancements in the synthesis of Veratrum alkaloids

• Morwenna Mögel,
• David Berger and
• Philipp Heretsch

Beilstein J. Org. Chem. 2025, 21, 2657–2693, doi:10.3762/bjoc.21.206

• of green for strategic connections, yellow for neutral, e.g., functional group interconversion and isomerization, orange for non-strategic reactions, and red for protecting group (PG) manipulations (Scheme 3). Protecting group manipulations refer to any protection or deprotection of a functional

• introduction of the F-ring and isomerization of the exo-methylene motif in the D-ring. First, the nitrogen was introduced via an α-azidation of the lactone, which itself was then reduced to a lactol, enabling a Horner–Wadsworth–Emmons (HWE) reaction with phosphonate 28 to provide 29. Peterson olefination

• gave the protected sulfonamide 30. For the isomerization of the exo-double bond, an Alder-ene reaction with N-sulfinylbenzenesulfonamide and subsequent desulfurization was the way of choice. Finally, both remaining protecting groups were removed to furnish cyclopamine (6). In total, 6 was prepared in

Recent advances in total synthesis of illisimonin A

• Juan Huang and
• Ming Yang

Beilstein J. Org. Chem. 2025, 21, 2571–2583, doi:10.3762/bjoc.21.199

• the same pot to give 72. Isomerization of the allylic methyl ether to an enol methyl ether was achieved using Crabtree’s catalyst in refluxing THF. Subsequent ketalization with the primary alcohol yielded the bridged ketal 73. A Schenck ene reaction on 73 induced the second olefin isomerization

• -catalyzed oxidative lactonization, yielding 76 with a newly established quaternary center at C1 and isomerization of the double bond to C2=C3. Photocatalyzed isomerization of the C2–C3 double bond in 76 to C3=C4 furnished 77 [39][40]. A Mukaiyama hydration introduced a hydroxy group at C4, accompanied by

Total syntheses of highly oxidative Ryania diterpenoids facilitated by innovations in synthetic strategies

• Zhi-Qi Cao,
• Jin-Bao Qiao and
• Yu-Ming Zhao

Beilstein J. Org. Chem. 2025, 21, 2553–2570, doi:10.3762/bjoc.21.198

• reaction with allyltributylstannane, yielding compound 40. After isomerization of the C11 allyl double bond and introduction of a C6 isobutenyl group, the resulting diene 42 underwent RCM catalyzed by the Hoveyda–Grubbs catalyst to form the pentacyclic skeleton 43, thus completing the C ring of the natural

Effect of a photoswitchable rotaxane on membrane permeabilization across lipid compositions

• Udyogi N. K. Conthagamage,
• Lilia Lopez,
• Zuliah A. Abdulsalam and
• Víctor García-López

Beilstein J. Org. Chem. 2025, 21, 2498–2512, doi:10.3762/bjoc.21.192

• bilayers through the shuttling of the macrocycle carrying the ions or through a relay mechanism [10][11]. In one example, the isomerization of an azobenzene photoswitch incorporated into the axle was used to modulate the shuttling rate of the macrocycle and, consequently, the efficiency of potassium ion

• minimal disruption of lipid packing appears to promote water accumulation in this system, and these dominant effects preclude assessing additional contributions from azobenzene isomerization. Likewise, upon light irradiation, rotaxane 2 and axle 3 induced dye release levels (65% and 54%, respectively

• E isomer and residing deeper within the bilayer in the Z isomer. Accordingly, this change in membrane localization influences water accumulation and disrupts lipid packing, thereby modulating membrane permeability. However, even though isomerization still occurs in the more rigid and thicker EYPC

The intramolecular stabilizing effects of O-benzoyl substituents as a driving force of the acid-promoted pyranoside-into-furanoside rearrangement

• Alexey G. Gerbst,
• Sofya P. Nikogosova,
• Darya A. Rastrepaeva,
• Dmitry A. Argunov,
• Vadim B. Krylov and
• Nikolay E. Nifantiev

Beilstein J. Org. Chem. 2025, 21, 2456–2464, doi:10.3762/bjoc.21.187

• , transformation of galactopyranosides to galactofuranosides under the action of TsOH in methanol [29] and silica-supported perchloric acid [30] is known. However, in both these cases di-O-isopropylidene ketals were used that underwent removal upon the isomerization leading to the loss of the aglycon. Recently, we

• resource by Shinya Fushinobu [39]. Results and Discussion In this study three examples of the pyranoside into furanoside isomerization were examined. The first one represented a case where methyl β-ᴅ-galactoside 1 was involved and the reaction resulted in a considerable amount of the furanose form in the

• equilibrium mixture (Figure 3A). Other two examples were the cases in which the isomerization to furanoside gave only minute quantities of product in the equilibrium or did not occur at all (Figure 3B and 3C). We used a DFT B3LYP-D3 approach to study possible driving forces of these reactions. First, the

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

• ring contraction of (S,S)-carveol-derived TBS ether 163b with triethylborane (Scheme 31). This reaction proceeded with isomerization and formation of the intermediate carbocation 181, which underwent 1,2-carbon migration to form the cyclopentane product 182. A sequence of oxidations of borane 182 with

• converted by a series of synthetic transformations to (−)-spirochensilide A (228) with a total yield of 2.2% in 22 steps starting from acetylenic epoxide 229. 4.1 Wagner–Meerwein rearrangement The isomerization of terpenes via cleavage, addition or nucleophilic substitution reactions accompanied by a

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

• ) has led to limitations on the use of chlorinated solvents, toluene, DMF etc., with the implementation of particular prerequisites [89]. The double bond present in oleic acid and methyl oleate may be disadvantageous for these solvents in comparison to methyl laurate. The potential isomerization and

Synthetic study toward vibralactone

• Liang Shi,
• Jiayi Song,
• Yiqing Li,
• Jia-Chen Li,
• Shuqi Li,
• Li Ren,
• Zhi-Yun Liu and
• Hong-Dong Hao

Beilstein J. Org. Chem. 2025, 21, 2376–2382, doi:10.3762/bjoc.21.182

• featuring a novel Pd-catalyzed β-lactone formation [29]. In addition to these approaches, Nelson and co-workers reported a very concise and impressive total synthesis of vibralactone involving photochemical valence isomerization of substituted pyrone, cyclopropanation, and ring expansion [30]. Zeng, Liu and

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

• or upon irradiation with light at 280 nm. Azobenzene Azobenzene is one of the most widely utilized photoresponsive units in the design and synthesis of photoswitchable rotaxanes. These photoswitches undergo trans–cis isomerization and are classified as T-type, due to the thermal reversibility of the

• isomerization (Figure 2) [29]. In 1997, Nakashima and co-workers reported the first rotaxane where the azobenzene was located on the axle, acting as a recognition site for a β-cyclodextrin macrocycle. Photoisomerization of the azobenzene controlled the shuttling of the macrocycle [30]. Later, Stoddart and co

• -workers developed a rotaxane where the azobenzene was located between two phenyl rings that work as recognition sites for a CBPQT4+ macrocycle. Likewise, isomerization of the azobenzene modulates the shuttling of the macrocycle among the recognition sites [31]. In the same year, Anderson and co-workers

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

• -strain between the methyl group at C10 and the substituent at C8 restricts the free rotation of the C8–C13 bond (although this steric hindrance can be circumvented through chair–boat isomerization of the six-membered ring, the barrier for this isomerization is relatively high), resulting in a

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

• isomerization reactions of cyclic meso-epoxides as part of a bimetallic titanium/cobalt catalytic system [64]. Photoredox catalysis in radical reactions The ability of a photocatalyst (organic small molecule or transition-metal complex) to undergo single electron transfer (SET) to a variety of organic

Pathway economy in cyclization of 1,n-enynes

• Hezhen Han,
• Wenjie Mao,
• Bin Lin,
• Maosheng Cheng,
• Lu Yang and
• Yongxiang Liu

Beilstein J. Org. Chem. 2025, 21, 2260–2282, doi:10.3762/bjoc.21.173

• 2021, the Shibata group reported a gold-catalyzed ring isomerization strategy to synthesize medium-sized nitrogen heterocycles (Scheme 12) [19]. The seven-membered dibenzo[b,d]azepine and eight-membered dibenzo[b,d]azocine frameworks were successfully obtained through the modulation of alkyne terminal

• /cycloisomerization sequences. In 2019 and 2020, Liu and co-workers achieved pathway-controlled cyclization–isomerization of tryptamine-ynamides using ligand-influenced silver catalytic systems (Scheme 19) [27][28][29]. To circumvent decomposition caused by the inherent high reactivity of ynamides under catalytic

• (Scheme 28, path b). When IPrAuNTf2 was used as the catalyst, product 138 was obtained via a 6-exo-dig cyclization, whereas when Ph3PAuNTf2 was employed as the catalyst, product 139 was exclusively obtained through a hydroarylation/isomerization/elimination pathway. This work disclosed an unprecedented

Pd-catalyzed dehydrogenative arylation of arylhydrazines to access non-symmetric azobenzenes, including tetra-ortho derivatives

• Loris Geminiani,
• Kathrin Junge,
• Matthias Beller and
• Jean-François Soulé

Beilstein J. Org. Chem. 2025, 21, 2234–2242, doi:10.3762/bjoc.21.170

• of applications, including molecular switches, sensors, and light-controlled materials [1][2][3][4][5][6][7][8]. The photoswitching behavior arises from the reversible photoisomerization between the E- and Z-forms of the azobenzene chromophore, driven by the isomerization of the N–N double bond. This

C2 to C6 biobased carbonyl platforms for fine chemistry

• Jingjing Jiang,
• Muhammad Noman Haider Tariq,
• Florence Popowycz,
• Yanlong Gu and
• Yves Queneau

Beilstein J. Org. Chem. 2025, 21, 2103–2172, doi:10.3762/bjoc.21.165

• catalysis. The mechanism first involves the isomerization of xylose into xylulose under Lewis acid-type catalysis, and the subsequent dehydration of xylulose into furfural under Brønsted acid-type catalysis (Scheme 47). Humins are naturally formed in all processes involving the acid-catalyzed degradation of

• isomerization and hydrogenation (Scheme 70, route b2). The accepted mechanism of the rehydration of HMF under acidic conditions leading to the formation of levulinic acid and formic acid proposed by Horvat [224] is depicted in Scheme 71. Levulinic acid can be converted into various derivatives, such as esters

Solar thermal fuels: azobenzene as a cyclic photon–heat transduction platform

• Jie Yan,
• Shaodong Sun,
• Minghao Wang and
• Si Wu

Beilstein J. Org. Chem. 2025, 21, 2036–2047, doi:10.3762/bjoc.21.159

• thermal fuels based on photoswitchable molecules are highly promising candidates for capturing and storing solar energy as heat [6][7]. In such systems, low-energy ground-state molecules absorb solar radiation and undergo isomerization to form high-energy photoexcited states (metastable configurations

• [47], where the azobenzene moieties undergo reversible photoisomerization and thermally induced reverse isomerization, enabling "energy charging–discharging" cycles (Figure 4a). Under ultraviolet (UV) irradiation (254 nm), the closely packed diacetylene polymers undergo polymerization to form π

• visible light under sunlight irradiation [59], achieving a solar efficiency of 0.4% and a solid-state isomerization efficiency of 72.7% (Figure 5b). Feng and co-workers reported the synthesis of three azopyridine polymers (ortho-, meta-, and para-) [60], with the m-azopyridine polymer exhibiting a

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

• Leticia A. Gomes and
• Steven A. Lopez

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

• starting materials for different types of reactions including thermal isomerization to cyclopentenes [36][37][38] and 1,4-pentadienes [37][38], chemical electron-transfer oxidations to cyclopentene [39] and cycloaddition reactions with electron-deficient alkenes and alkynes [38][40][41] (Scheme 1b

Enantioselective desymmetrization strategy of prochiral 1,3-diols in natural product synthesis

• Lihua Wei,
• Rui Yang,
• Zhifeng Shi and
• Zhiqiang Ma

Beilstein J. Org. Chem. 2025, 21, 1932–1963, doi:10.3762/bjoc.21.151

• into (−)-talaromycin B (232) in six steps. For (+)-talaromycin A (235) (Scheme 28b), a three-step transformation of 230 gave 233, and subsequent isomerization at the C6 spirocenter with TFA produced compound 234, which was converted into 235 in three additional steps. The introduction of an inducing

Synthesis of N-doped chiral macrocycles by regioselective palladium-catalyzed arylation

• Shuhai Qiu and
• Junzhi Liu

Beilstein J. Org. Chem. 2025, 21, 1917–1923, doi:10.3762/bjoc.21.149

• rings. In the molecular arrangement, a pair of enantiomers exists in each cell for MC3 (Figure 2d). Considering the C–C single bonds between the π-subunits, isomerization among different molecular configurations might occur via rotations. To further investigate the conformational stability of MC3

• , theoretical calculations were performed to evaluate the energy barriers of isomerization. As shown in Figure S3 (Supporting Information File 1), the configuration observed in the crystal structure has the lower energy by 24.0 kcal mol−1 than that of the isomeric structure with two pyrene units at the same

Chiral phosphoric acid-catalyzed asymmetric synthesis of helically chiral, planarly chiral and inherently chiral molecules

• Wei Liu and
• Xiaoyu Yang

Beilstein J. Org. Chem. 2025, 21, 1864–1889, doi:10.3762/bjoc.21.145

• removing the less soluble racemic products. Detailed studies were conducted to explore the reaction mechanism, focusing specifically on the role of the 2-acylanilines 73 as co-catalysts. Based on the experimental results and previous research, a plausible mechanism was proposed. Isomerization of substrates

Research progress on calixarene/pillararene-based controlled drug release systems

• Liu-Huan Yi,
• Jian Qin,
• Si-Ran Lu,
• Liu-Pan Yang,
• Li-Li Wang and
• Huan Yao

Beilstein J. Org. Chem. 2025, 21, 1757–1785, doi:10.3762/bjoc.21.139

• -affinity host–guest interactions between PA5 and these groups (mainly through phosphonate-quaternary ammonium ion pairing) [90]. Azobenzene guest molecules can achieve dual functions (on and off) as ligands through photo-induced cis-trans isomerization. Using pillar[6]arene as the ion channel, the host

• employed as an external trigger for supramolecular systems. Azobenzene can regulate geometry, shape, and interfacial curvature under ultraviolet or visible light irradiation. It undergoes cis–trans isomerization, which can trigger alterations in bioactivity or assembly configurations. Methods for creating

Preparation of a furfural-derived enantioenriched vinyloxazoline building block and exploring its reactivity

• Madara Darzina,
• Anna Lielpetere and
• Aigars Jirgensons

Beilstein J. Org. Chem. 2025, 21, 1737–1741, doi:10.3762/bjoc.21.136

• methoxymethyl group cleavage, O-to-N rearrangement, and isomerization of the double bond. An oxazoline ring formation in the resulting unsaturated amides provided the corresponding enantioenriched vinyloxazoline. The reactivity of the electron-deficient double bond in the vinyloxazoline was explored in several

• electrolysis conditions and its removal was compatible with the double bond and acetal functions in ester 3d (see Supporting Information File 1 for attempts of other protecting groups such as Boc, Troc, and tfa). However, Pd-catalyzed N-Alloc deprotection induced isomerization of the double bond leading to the