Modern synthetic pathways towards eribulin and its subunits

• Sebastian Dominik Graf

Beilstein J. Org. Chem. 2026, 22, 495–526, doi:10.3762/bjoc.22.37

• proved to be suitable for the cyclization towards 35 and the eventual macrocyclization was achieved via coupling of the alkyl bromide unit with the thioester. Mechanistically, this reaction is enabled by the formation of an intermediate alkylzinc halide, which is produced by single electron transfer

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

• products were detected under the optimized conditions (Scheme 2). Based on our previous reports [48][56], DFT calculations, and cyclic voltammetry (CV) analyses (Figure 1), anodic single-electron transfer (SET) is expected to occur first from 3, generating the electrophilic radical cation [3]·+ as 3 (Eox

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

• a radical pathway. Selectfluor undergoes a single-electron transfer (SET) with Cu(II) to generate the dicationic radical species AI, which abstracts a hydrogen atom from the PMB group to form a benzylic radical intermediate AJ. A subsequent SET process generates an acyliminium intermediate AK, which

• aniline furnishing acetylanilide 158 in 87% yield. A wide range of arylamines bearing electron-donating or electron-withdrawing substituents, as well as heteroarylamines, were also competent nucleophiles, delivering the corresponding amides 159–161 in good yields. EPR studies suggested a single-electron

• -transfer (SET)-driven mechanism. Coordination of the arylamine to the potassium cation followed by deprotonation generates potassium amide salt AB. A SET process forms amine radical AC, which then transfers an electron to the amide, generating radical anion AD. Coupling of AC and AD forms a tetrahedral

Ring contraction and ring expansion reactions in terpenoid biosynthesis and their application to total synthesis

• Nicolas Kratena,
• Nicolas Heinzig and
• Peter Gärtner

Beilstein J. Org. Chem. 2026, 22, 289–343, doi:10.3762/bjoc.22.21

• diradical at the unsaturated ketone (62a), cyclisation to form an intermediary highly substituted cyclopropane (62b) followed by single-electron transfer to the zwitterionic 62c and rearrangement to either the dense connectivity of lumisantonin (63), or carbocation capture by solvolysis of intermediate 64a

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

• reduction of activated aromatic cations (e.g., pyridinium, quinolinium, or benzopyrylium salts), offering mild and chemoselective access to partially or fully saturated heterocycles. More recent advances in single-electron transfer (SET) chemistry, particularly those mediated by photoredox catalysts or

Advances in Zr-mediated radical transformations and applications to total synthesis

• Hiroshige Ogawa and
• Hugh Nakamura

Beilstein J. Org. Chem. 2026, 22, 71–87, doi:10.3762/bjoc.22.3

• hydrogen atom from 1,4-cyclohexadiene to furnish the alcohol product. The active species Cp2ZrIII(OTf) is then regenerated via single-electron transfer (SET) from the Ir photocatalyst. Notably, the addition of thiourea 26 significantly improved the regioselectivity in this reaction. According to NMR

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

• and the acylazolium complex B (Ep = −0.81 V vs SCE), single-electron transfer (SET) reduction of B was thermodynamically feasible; however, the efficiency was found to be significantly low. The oxidation potential was measured to be around [Ep = +0.72 V] vs SCE, indicating that it is sufficiently

Synthesis of the tetracyclic skeleton of Aspidosperma alkaloids via PET-initiated cationic radical-derived interrupted [2 + 2]/retro-Mannich reaction

• Ru-Dong Liu,
• Jian-Yu Long,
• Zhi-Lin Song,
• Zhen Yang and
• Zhong-Chao Zhang

Beilstein J. Org. Chem. 2025, 21, 2470–2478, doi:10.3762/bjoc.21.189

• intricacies of the key PET reaction for formation of the unique bicyclo[2.2.0]hexane unit present in the proposed intermediate L (Figure 1). In the presence of the excited photocatalyst [FCNIr(III)Pic]*, the substrate participates in an oxidative single-electron transfer (SET) process, which leads to the

An Fe(II)-catalyzed synthesis of spiro[indoline-3,2'-pyrrolidine] derivatives

• Elizaveta V. Gradova,
• Nikita A. Ozhegov,
• Roman O. Shcherbakov,
• Alexander G. Tkachenko,
• Larisa Y. Nesterova,
• Elena Y. Mendogralo and
• Maxim G. Uchuskin

Beilstein J. Org. Chem. 2025, 21, 2383–2388, doi:10.3762/bjoc.21.183

• bond cleavage to generate an N-imidoyl radical intermediate that undergoes intramolecular cyclization to yield the spirocyclic product (Scheme 1, path g) [14]. Notably, iron is known to exhibit similar behavior in single-electron transfer (SET) processes [15][16][17]. In fact, we previously

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

• can further undergo ring-opening or rearrangement reaction to assemble complex molecular frameworks. Additionally, quinone photoredox reactions involving single-electron transfer (SET) processes provide novel strategies for the stereoselective synthesis of useful structures such as spiroketals. This

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

• include the use of transition metals or photoredox catalysts. In photoredox catalysis, radical generation often involves single-electron transfer (SET) to or from a photoexcited state of a photoredox catalyst, usually a metal complex or organic molecule. Two other notable strategies for radical generation

• ]. MacMillan obtained chiral free radicals by stoichiometric single electron transfer (SET) oxidation of enamines, formed by the reaction between chiral secondary amines and aldehydes. This mode of activation was called SOMO (singly occupied molecular orbital) catalysis and was employed in several organic

• 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

Electrochemical cyclization of alkynes to construct five-membered nitrogen-heterocyclic rings

• Lifen Peng,
• Ting Wang,
• Zhiwen Yuan,
• Bin Li,
• Zilong Tang,
• Xirong Liu,
• Hui Li,
• Guofang Jiang,
• Chunling Zeng,
• Henry N. C. Wong and
• Xiao-Shui Peng

Beilstein J. Org. Chem. 2025, 21, 2173–2201, doi:10.3762/bjoc.21.166

• ] generated [Cp2Fe]+ along with cathodic reduction of MeOH to H2 and MeO− acting as a base. Deprotonation of 1a using MeO− produced the anion A, which underwent single-electron transfer (SET) with [Cp2Fe]+ to give the nitrogen-centered radical B with regeneration of [Cp2Fe] [164][165][166][167][168][169][170

• a plausible reaction mechanism. Initially, the anodization of diphenyl diselenide produced phenylselenium radical A and selenium cation B, the single-electron transfer on the anode could also transformed A into B. Addition of B to 37a formed the intermediate C that underwent intramolecular

• along with the generation of OH− through reduction of H2O at the cathode. In the presence of OH−, deprotonation of 48 underwent smoothly to generate the anion species B. The single-electron transfer from B to A gave amidyl radical C with the regeneration of 47. The 5-exo-dig annulation of C provided

Photochemical reduction of acylimidazolium salts

• Michael Jakob,
• Nick Bechler,
• Hassan Abdelwahab,
• Fabian Weber,
• Janos Wasternack,
• Leonardo Kleebauer,
• Jan P. Götze and
• Matthew N. Hopkinson

Beilstein J. Org. Chem. 2025, 21, 1973–1983, doi:10.3762/bjoc.21.153

• photocatalyst radical anion ([PC]·−) and the DIPEA radical cation D (Scheme 1). Single-electron transfer from [PC]·− to the benzoylazolium species 1 would then regenerate the ground-state photocatalyst and afford the Breslow radical anion C, which could in turn react with D in a hydrogen-atom-transfer (HAT

• conditions monitored over 48 h by 1H NMR. Plausible mechanism for the photocatalytic reduction of benzoylimidazolium salt 1 with DIPEA. [PC] = photocatalyst; SET = single-electron transfer; HAT = hydrogen atom transfer. Plausible mechanism for the photocatalyst-free reduction of benzoylimidazolium salt 1

General method for the synthesis of enaminones via photocatalysis

• Paula Pérez-Ramos,
• Raquel G. Soengas and
• Humberto Rodríguez-Solla

Beilstein J. Org. Chem. 2025, 21, 1535–1543, doi:10.3762/bjoc.21.116

• . Simultaneously, acridinium photocatalyst PC1 absorbed energy and transitioned from the ground state to excited state under visible-light irradiation. This excited state PC1* is quenched by the amine, generating the amine radical cation and PC1 radical via a single-electron transfer (SET) process. Then, the C−Br

Photoredox-catalyzed arylation of isonitriles by diaryliodonium salts towards benzamides

• Nadezhda M. Metalnikova,
• Nikita S. Antonkin,
• Tuan K. Nguyen,
• Natalia S. Soldatova,
• Alexander V. Nyuchev,
• Mikhail A. Kinzhalov and
• Pavel S. Postnikov

Beilstein J. Org. Chem. 2025, 21, 1480–1488, doi:10.3762/bjoc.21.110

• reactivity pattern in the current transformation, a reaction mechanism was proposed taking into the account the known data and control experiments (Scheme 4). Upon irradiation with blue light, the Ru(II) catalyst undergoes photoexcitation, followed by an oxidative single-electron transfer (SET) process with

Oxetanes: formation, reactivity and total syntheses of natural products

• Peter Gabko,
• Martin Kalník and
• Maroš Bella

Beilstein J. Org. Chem. 2025, 21, 1324–1373, doi:10.3762/bjoc.21.101

• reduction of the Ni(II) pre-catalyst) via oxidative addition, radical coupling and reductive elimination. The last step is a single-electron transfer between the resulting Ir(II) and Ni(I) complexes, regenerating the active catalysts and closing the two cycles. In 2021, Romanov-Michailidis and Knowles et al

Recent advances in amidyl radical-mediated photocatalytic direct intermolecular hydrogen atom transfer

• Hao-Sen Wang,
• Lin Li,
• Xin Chen,
• Jian-Li Wu,
• Kai Sun,
• Xiao-Lan Chen,
• Ling-Bo Qu and
• Bing Yu

Beilstein J. Org. Chem. 2025, 21, 1306–1323, doi:10.3762/bjoc.21.100

• amidyl radicals from HRP: (a) direct single-electron oxidation of amide HRP in the presence of photocatalyst and a base via a proton-coupled electron transfer (PCET) process by the cleavage of the N–H bond; (b) single-electron reduction of HRP catalyzed by photocatalyst via a single-electron transfer

Recent advances in oxidative radical difunctionalization of N-arylacrylamides enabled by carbon radical reagents

• Jiangfei Chen,
• Yi-Lin Qu,
• Ming Yuan,
• Xiang-Mei Wu,
• Heng-Pei Jiang,
• Ying Fu and
• Shengrong Guo

Beilstein J. Org. Chem. 2025, 21, 1207–1271, doi:10.3762/bjoc.21.98

• -mediated process. Based on the experimental results, a detailed reaction mechanism was proposed (Scheme 8). The reaction begins with the oxidative cleavage of an α-C(sp3)–H bond in acetonitrile (15) by the Sc(OTf)3/Ag2O system, generating an alkyl radical A through a single-electron-transfer (SET) process

• the cathode. This deprotonation leads to the formation of a carbanion, which undergoes single-electron transfer (SET) with Cp2Fe+, resulting in the generation of a carbon-centered radical. This radical subsequently undergoes intramolecular cyclization with the aryl ring to form the final oxindole or

• experiments, which suggested that the transformation proceeds via a radical pathway. The proposed mechanism begins with the excitation of 4CzIPN by visible light, followed by a single-electron transfer that generates a radical intermediate (Scheme 28). A cascade of bond-forming reactions then occurs, leading

Recent advances in synthetic approaches for bioactive cinnamic acid derivatives

• Betty A. Kustiana,
• Galuh Widiyarti and
• Teni Ernawati

Beilstein J. Org. Chem. 2025, 21, 1031–1086, doi:10.3762/bjoc.21.85

• nitrilium salt 92 followed by carboxylate attack (93) and Mumm rearrangement (Scheme 27) [63]. Furthermore, Maruoka and co-workers (2020) developed a one-pot transamidation reaction catalyzed by Cu via acid fluoride 48 (Scheme 28) [64]. In this work, single-electron transfer (SET) between Selectfluor and

Recent advances in controllable/divergent synthesis

• Jilei Cao,
• Leiyang Bai and
• Xuefeng Jiang

Beilstein J. Org. Chem. 2025, 21, 890–914, doi:10.3762/bjoc.21.73

• mechanistic experiments and DFT calculations, the authors proposed a possible mechanism for the reaction: first, DPZ is excited by light to form the excited state DPZ*, which then oxidizes bromide ions through single-electron transfer to generate corresponding radical anions. These radical anions undergo

• single-electron transfer with substrate 72 to form radical intermediate Int-70, completing the DPZ catalytic cycle. Intermediate Int-70 adds to substrate 73 to form radical intermediate Int-71, which further adds to hydrogen-bond-activated substrate 74 to form hydrogen-bonded complex Int-72. When Na3PO4

• is used as the inorganic base, bromine radicals abstract hydrogen to form product 75; whereas when Na2HPO4 is used as the inorganic base, its weaker basicity leads to protonation of complex Int-72 to form intermediate Int-73, which then preferentially undergoes single-electron transfer with the DPZ

Light-enabled intramolecular [2 + 2] cycloaddition via photoactivation of simple alkenylboronic esters

• Lewis McGhie,
• Hannah M. Kortman,
• Jenna Rumpf,
• Peter H. Seeberger and
• John J. Molloy

Beilstein J. Org. Chem. 2025, 21, 854–863, doi:10.3762/bjoc.21.69

• detrimental to reactivity leading to substrate degradation. Given the ease of access and enhanced stability of pinacol esters to column chromatography, this motif was advanced for further reaction design. Cyclic voltammetry analysis of 1a indicates that single-electron-transfer processes with the excited

Formaldehyde surrogates in multicomponent reactions

• Cecilia I. Attorresi,
• Javier A. Ramírez and
• Bernhard Westermann

Beilstein J. Org. Chem. 2025, 21, 564–595, doi:10.3762/bjoc.21.45

• salts and TEMPO as the radical initiator/oxidant couple that promoted the intramolecular radical cyclization of suitable 1,3-dicarbonyl Ugi adducts 54 and 55 (Scheme 45) [108][109]. The stabilization of the enol in the 1,3-dicarbonyl Ugi adduct allows single-electron transfer (SET) with the anion

Photomechanochemistry: harnessing mechanical forces to enhance photochemical reactions

• Francesco Mele,
• Ana M. Constantin,
• Andrea Porcheddu,
• Raimondo Maggi,
• Giovanni Maestri,
• Nicola Della Ca’ and
• Luca Capaldo

Beilstein J. Org. Chem. 2025, 21, 458–472, doi:10.3762/bjoc.21.33

• transform molecules. Intriguingly, photocatalysts typically absorb harmless visible light and can be chosen ad hoc to trigger the desired chemistry. Indeed, the photocatalyst–substrate interaction can occur via energy transfer [4][5][6][7][8], single-electron transfer [9][10][11][12], or hydrogen-atom

• in enhancing the mixing efficiency and increasing the exposure of the surface of the reaction mixture to light. Additionally, the formation of compound 8.2 was associated with the observation of an initial molten state of the mixture, which could have promoted single-electron-transfer processes that

Electrochemical synthesis of cyclic biaryl λ³-bromanes from 2,2’-dibromobiphenyls

• Andrejs Savkins and
• Igors Sokolovs

Beilstein J. Org. Chem. 2025, 21, 451–457, doi:10.3762/bjoc.21.32

• oxidation) and 6b (one-electron oxidation) into the respective bromine(III) species (Scheme 3C) [17] demonstrated a more similar behaviour to 6b suggesting that revealed oxidation is a single-electron-transfer process. It is important to note that this comparison assumes that the diffusion coefficients of

Red light excitation: illuminating photocatalysis in a new spectrum

• Lucas Fortier,
• Corentin Lefebvre and
• Norbert Hoffmann

Beilstein J. Org. Chem. 2025, 21, 296–326, doi:10.3762/bjoc.21.22

• unsaturated ring structure derived from squaric acid [47], has attracted attention due to its ability to promote single-electron transfer [48]. These compounds exhibit significant NIR fluorescence, making them valuable in applications such as biomolecule probing. Additionally, squaraine derivatives are well

• of these compounds in the field of photocatalysis [49]. The study has included a detailed mechanistic investigation to differentiate between competing single-electron transfer and energy transfer pathways. Through both experimental measurements and theoretical calculations, the authors have

• and mechanistic investigations of the near-IR-photocatalyzed aza-Henry reaction, the authors have proposed either a single-electron transfer or an energy transfer mechanism. Additionally, the reaction displayed an unexpected sensitivity to the light wavelength used. Employing a higher-energy light