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

• -rich and electron-poor substituents. This reaction was carried out between arylcyclopropanes 5 and acyl fluoride 4 in the presence of NHC (10 mol %) and 4CzIPN (5 mol %). Mechanistic studies showed that the cascade proceeds via nucleophilic ring-opening of a cyclopropyl radical cation D with subsequent

• substrate 7, generating the aryl radical cation C along with the formation of corresponding radical anion of the photocatalyst (PC•–). The reduction potentials are (E1/2(P/P•–) = –1.37V vs SCE for [Ir(dF(CF₃)ppy)₂(dtbbpy)]PF₆ and –1.21V vs SCE for 4CzIPN as an organophotocatalyst. This method permits the C

• was described. Aromatic C(sp2)–H bond acylation was achieved by dual catalysis through cooperative NHC and organophotoredox-catalyzed C–C cross-coupling of a benzo-fused aryl radical cation C with stable ketyl radical B as the key step. LED irradiation of photocatalyst leads to photoexcited PC*, which

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

• cation were consistent with earlier reports [2][26], though the configurations of the intermediates were clearly delineated. The authors proposed that dicarbonyl compound 50 serves as the key intermediate diverging to all Illicium sesquiterpenes, with a retro-Dieckmann condensation and aldol reaction

Ni-promoted reductive cyclization cascade enables a total synthesis of (+)-aglacin B

• Si-Chen Yao,
• Jing-Si Cao,
• Jian Xiao,
• Ya-Wen Wang and
• Yu Peng

Beilstein J. Org. Chem. 2025, 21, 2548–2552, doi:10.3762/bjoc.21.197

• (2) and C (3), featuring a visible light-catalyzed radical cation cascade for the formation of the C8–C8′ and C2–C7′ bonds [6]. Subsequently, they improved the reaction conditions to achieve the racemic synthesis of aglacins A (1) and E (4) as well [7]. In 2021, the Gao group described the total

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

• current interest in the synthesis of complex natural products via photochemical reactions, we decided to achieve such an unusual bond cleavage (Figure 1a, path A) of cyclobutenone by generating a radical cation species via a PET reaction. The synthetic plan is shown in Figure 1c and includes a PET

• -initiated [2 + 2] cyclization of the tryptamine-substituted cyclobutenone K to form the radical cation L, which has a highly functionalized and rigid bicyclo[2.2.0]hexane core. Fragmentation of the C3–C19 bond would afford a redox-active intermediate which upon further reductive quenching would lead to the

• formation of IN1. The radical cation IN1 served as the reference point for DFT investigations. As illustrated in Figure 2a, facilitated by a favorable radical cation–π interaction [31], IN1 proceeds to the first radical addition transition state (TS1), with an energy barrier of 8.3 kcal/mol. This leads to

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

• acted as nucleophile, the stable imine–gold–aryl cation–π–π interaction precluded rearrangement and promoted the capture of imine to form spiro[indoline-3,3'-pyridine] derivatives 67. The Ph3PAuCl/AgNTf2-catalyzed cyclization of N-propargyl-tethered amide enynes efficiently afforded four distinct

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

• occurred to give a radical cation PhSeSePh•+ at the anode. The subsequent cleavage of Se–Se bond formed a radical PhSe• and a cation PhSe+. Further additional oxidation of PhSe• yielded another PhSe+, which worked as the major reactive species and quickly added to C≡C in 13a to form intermediate A. Finally

• phenylselenium cation C and phenylselenium radical B through radical cation species A. Simultaneously, the cathodic reduction of 17a generated anion D and radical B. Then, addition of B with the alkyne portion in 16a gave a radical intermediate E, which proceeded a one-electron oxidation followed by nucleophilic

• addition and then deprotonation to yield the desired 18a via intermediate G. Another possible pathway is that phenylselenium cation C attacked 16a afforded the alkenyl cation G, which underwent cyclization and deprotonation to produce 18a. It should be noted that this conversion proceeded under metal

Bioinspired total syntheses of natural products: a personal adventure

• Zhengyi Qin,
• Yuting Yang,
• Nuran Yan,
• Xinyu Liang,
• Zhiyu Zhang,
• Yaxuan Duan,
• Huilin Li and
• Xuegong She

Beilstein J. Org. Chem. 2025, 21, 2048–2061, doi:10.3762/bjoc.21.160

• TBS protection in one pot. Oxidation of the primary alcohol using Swern oxidation gave the hydroxy aldehyde 3, which was activated with a formal silicon cation to trigger the Prins cyclization terminated by the tertiary alcohol, affording silylated bicycle 9 directly through the designed bioinspired

• oxa-carbenium cation triggered by an acid to proceed a Friedel–Crafts reaction to afford the dibenzocyclooctene skeleton. On the other hand, eupomatilone would undergo redox transformations to generate another oxa-carbenium cation to undergo a Friedel–Crafts reaction to form a spirocyclic skeleton

• . This oxa-carbenium cation could also undergo hydrolysis to provide a linear skeleton with a hydroxy ketone moiety, and this hydrolysis process is reversible. It is worth noting that Zhou explored the chemical conversion of the eupodienone skeleton to the eupomatilone skeleton through acid-promoted

Aryl iodane-induced cascade arylation–1,2-silyl shift–heterocyclization of propargylsilanes under copper catalysis

• Rasma Kroņkalne,
• Rūdolfs Beļaunieks,
• Armands Sebris,
• Anatoly Mishnev and
• Māris Turks

Beilstein J. Org. Chem. 2025, 21, 1984–1994, doi:10.3762/bjoc.21.154

• stabilized allyl cation intermediates that undergo regioselective trapping by internal O- and N-nucleophiles furnishing functionalized heterocycles. This method provides access to tetrahydrofuran or pyrrolidine frameworks, each bearing a trifunctionalized (E)-configured vinyl side chain. The use of a shorter

• alkynes undergo 1,2-carbofunctionalization, where the highly electrophilic Ar–M species adds to the alkyne, generating a vinyl cation intermediate [7], which typically reacts with an internal nucleophile to form five- [8][9] or six-membered rings [7][9][10] (Scheme 1A). Thus far the internal nucleophilic

• rearrangements via the 1,2-silyl shift, enabled by the β-cation-stabilizing properties of silyl groups [19][20]. This phenomenon has been successfully employed in 1,3-difunctionalization events in both intermolecular [21] and intramolecular fashion [22] (Scheme 1B). Thus far such propargylsilane rearrangements

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

• electron to compound 3 could explain the formation of the fully reduced species 2. In this case, subsequent mesolysis would generate the benzyl radical cation G, which would deliver 2 following a HAT step with the DIPEA radical cation D. To confirm whether O-benzoylated species is indeed an intermediate in

Thermodynamics and polarity-driven properties of fluorinated cyclopropanes

• Matheus P. Freitas

Beilstein J. Org. Chem. 2025, 21, 1742–1747, doi:10.3762/bjoc.21.137

• 1.2.3-c.c., it is capable of interacting with ions and potentially acting as both an anion and a cation carrier. To evaluate this property, Na+ and Cl− ions were simulated in interaction with one and two molecules of 1.2.3-c.c., forming complexes akin to a "sandwich," as illustrated in Figure 3. In

• these complexes, the cation coordinates with the fluorine atoms, while the anion interacts with the positively charged hydrogen atoms. The complexation is thermodynamically favorable when compared to the isolated species (ions and 1.2.3-c.c.), as indicated by the ΔH0 of formation: −32.5 kcal mol−1 for

Influence of the cation in hypophosphite-mediated catalyst-free reductive amination

• Natalia Lebedeva,
• Fedor Kliuev,
• Olesya Zvereva,
• Klim Biriukov,
• Evgeniya Podyacheva,
• Maria Godovikova,
• Oleg I. Afanasyev and
• Denis Chusov

Beilstein J. Org. Chem. 2025, 21, 1661–1670, doi:10.3762/bjoc.21.130

• hypophosphorous acid are commercially available in bulk amounts, however, their usage is understudied in organic processes. While NaH2PO2 has proved to be an efficient four-electron reductant in the catalyst-free reductive amination, the influence of cation in hypophosphite salt has not been studied yet. This

• investigation of cation influence on the efficiency of reductive amination, a commercially available NaH2PO2, and in situ synthesized LiH2PO2, NaH2PO2, KH2PO2, RbH2PO2, and CsH2PO2 were compared. To account for the reactivity of H3PO2 as is, the reaction outcome both for the neutral XH2PO2 (where X is Li, Na, K

• has shown clear influence of the cation in the hypophosphite salt on the effectiveness of the reductive amination. The acidity of the reaction media was a key factor affecting the equilibrium in the interaction between carbonyl compounds and amines. Intermediately acidic media is the optimal for the

On the aromaticity and photophysics of 1-arylbenzo[a]imidazo[5,1,2-cd]indolizines as bicolor fluorescent molecules for barium tagging in the study of double-beta decay of ¹³⁶Xe

• Eric Iván Velazco-Cabral,
• Fernando Auria-Luna,
• Juan Molina-Canteras,
• Miguel A. Vázquez,
• Iván Rivilla and
• Fernando P. Cossío

Beilstein J. Org. Chem. 2025, 21, 1627–1638, doi:10.3762/bjoc.21.126

• fluorescent moieties constitute promising candidates to detect Ba2+ cations [8][9] (Figure 2). Another essential component is an aza-crown ether of appropriate dimensions to capture the barium cation. In addition, one para-disubstituted phenyl (or aryl) group is installed to generate selective cation–π

• efficiency of crown ethers as components in cation-selective fluorescent probes has been extensively explored [7][30], to the best of our knowledge no previous computational DFT studies on the selectivity of crown ethers of different sizes with Ba2+ have been reported. Therefore, we explored (Scheme 2A) the

• binding between this cation and 12-crown-4 (16a, n = 1), 15-crown-5 (16b, n = 2), 18-crown-6 (16c, n = 3) and 21-crown-7 (16d, n = 4), to form Ba2+·crown ethers 15a–d. We compared the corresponding binding energies by means of the following isodesmic equation: Where the different terms correspond to Gibbs

Thermodynamic equilibrium between locally excited and charge transfer states in perylene–phenothiazine dyads

• Issei Fukunaga,
• Shunsuke Kobashi,
• Yuki Nagai,
• Hiroki Horita,
• Hiromitsu Maeda and
• Yoichi Kobayashi

Beilstein J. Org. Chem. 2025, 21, 1577–1586, doi:10.3762/bjoc.21.121

• anion of the Pe moiety. Additionally, a shoulder signal observed near 500 nm was attributed to the radical cation of the PTZ(TPA) unit. However, although previous studies selectively excited the Pe moiety and attributed the 725 nm band to the LE state of Pe moiety, such an assignment may not be directly

• attributable to the Pe radical anion and the PTZ(TPA) radical cation appeared at ≈600 and ≈500 nm, respectively (Figure 7). The electron transfer time constant was determined to be 7.6 ps, significantly slower than that of Pe–PTZ(TPA)2 (120 fs or faster), reflecting the effect of the phenyl spacer that

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

• oxidative state PC1* that interacts with morpholine (8a) to generate the corresponding aminium radical cation. To gain a better understanding of the process, the formation of the enaminone product 9a was monitored overtime by 1H NMR, which confirmed that the the reaction was complete within 2 h. Furthermore

• . 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

Ambident reactivity of enolizable 5-mercapto-1H-tetrazoles in trapping reactions with in situ-generated thiocarbonyl S-methanides derived from sterically crowded cycloaliphatic thioketones

• Grzegorz Mlostoń,
• Małgorzata Celeda,
• Marcin Palusiak,
• Heinz Heimgartner,
• Marta Denel-Bobrowska and
• Agnieszka B. Olejniczak

Beilstein J. Org. Chem. 2025, 21, 1508–1519, doi:10.3762/bjoc.21.113

• terminal S‒CH2 position, leading to the formation of the sulfonium cation 11 and the delocalized heterocyclic anion 12 (Scheme 6). In the next step, competitive addition of both intermediate species yields either thioaminals 9 or dithioacetals 10. However, a slow isomerization of the thermodynamically less

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

• conditions is due to a favorable formation of EWG-substituted aryl radicals from the iodonium cation, based on their reduction potentials and bond-dissociation energies calculated by Romanczyk and Kurek [45]. The reduction potential in SET reactions for iodonium salts with EWG-substituted aryls significantly

Advances in nitrogen-containing helicenes: synthesis, chiroptical properties, and optoelectronic applications

• Meng Qiu,
• Jing Du,
• Nai-Te Yao,
• Xin-Yue Wang and
• Han-Yuan Gong

Beilstein J. Org. Chem. 2025, 21, 1422–1453, doi:10.3762/bjoc.21.106

• electronic behaviors reminiscent of nitrogen-doped azulenes, featuring strong absorption dissymmetry factors (|gabs|) at 345 nm – 1.2 × 10−2 for compound 20a, 1.0 × 10−2 for 20d, and 1.3 × 10−2 for 20e (Table 5). Notably, the radical cation form of compound 20e (20e•+) exhibits pronounced CD signals

• BCPL value of 13.2 M−1 cm−1. Notably, compound 21c undergoes reversible redox interconversion to its radical cation 21c•+ and dicationic 21c2+ states via chemical oxidation, enabling controllable switching between antiaromatic and aromatic configurations. These results provide a compelling strategy for

• | value of 1.6 × 10−3. In addition, both 29a and 29b demonstrate redox activity, undergoing reversible formation of radical anions, dianions, and radical cations. The radical cation 29b•+, in particular, exhibits a broad near-infrared (NIR) absorption band extending to 3000 nm, highlighting its potential

Tautomerism and switching in 7-hydroxy-8-(azophenyl)quinoline and similar compounds

• Lidia Zaharieva,
• Vera Deneva,
• Fadhil S. Kamounah,
• Nikolay Vassilev,
• Ivan Angelov,
• Michael Pittelkow and
• Liudmil Antonov

Beilstein J. Org. Chem. 2025, 21, 1404–1421, doi:10.3762/bjoc.21.105

• the diazonium salts are made alkaline the para-fluorine atom is so readily replaced by a hydroxy group, and that the 4-hydroxy-2,3,5,6-tetrafluorobenzene cation is the entity formed first [90][91]. A 50 mL round-bottomed flask equipped with a mini magnet was charged with pentafluoroaniline (0.64 g

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

• a preparation of oxetanes via silicon-directed electrophilic cyclisation of homoallylic alcohols 49 (Scheme 12) [46]. The reaction was promoted by a bromonium cation and moderate to high yields of oxetanes 50 were obtained. The authors claim the reaction was diastereospecific for disubstituted

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

• the concurrent generation of the carbon cation 55. This cation was subsequently trapped by a nucleophile, leading to the formation of product 54. This system demonstrated a broad applicability for the general nucleophilic amination of benzylic C–H bonds. The substrate's scope and selectivity were

• it into the byproduct 46 and generating a carbon-centered radical 62. Species 62 is trapped by heteroarene 60, leading to the formation of the intermediate 63. This intermediate 63 undergoes SET and proton transfer with the assistance of O-anion 64 and the Br-5CzBN+• radical cation, delivering the

Recent advances and future challenges in the bottom-up synthesis of azulene-embedded nanographenes

• Bartłomiej Pigulski

Beilstein J. Org. Chem. 2025, 21, 1272–1305, doi:10.3762/bjoc.21.99

• by a naphthalene-to-azulene rearrangement. The alternative radical cation mechanism has a higher energy barrier than the arenium cation-mediated reaction. Notably, only one of the pentagon–heptagon pairs exhibits an azulene-like electronic structure and aromaticity, as confirmed by the analysis of

• calculated NICS values. Similarly, Liu and co-workers reported the synthesis of two related nanographenes from precursor 38 (Scheme 6) [47]. Oxidation using DDQ/TfOH yielded two PAHs 39 and 40 in 34% and 22% yield, respectively. The authors postulated here formation of azulene moiety through radical cation

• ]. Notably, PAH 109 forms an air-stable radical cation after oxidation. A similar intramolecular oxidation of two adjacent azulene units was also reported with the use of FeCl3 as an oxidant [73] or in one step during Suzuki coupling between 1,8-dibromonaphthalene and borylated azulene [74]. The ease of

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

• cation B and an α-carbon radical A. The α-carbon radical A then undergoes intermolecular radical addition to the acrylamide, forming a new carbon-centered radical intermediate C, which subsequently undergoes intramolecular cyclization to yield the oxindole product 88a via homolytic aromatic substitution

Synthesis of β-ketophosphonates through aerobic copper(II)-mediated phosphorylation of enol acetates

• Alexander S. Budnikov,
• Igor B. Krylov,
• Fedor K. Monin,
• Valentina M. Merkulova,
• Alexey I. Ilovaisky,
• Liu Yan,
• Bing Yu and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2025, 21, 1192–1200, doi:10.3762/bjoc.21.96

• . Alternatively, 3 can be formed by hydrolysis of benzylic cation I [71]. Conclusion In summary, we have disclosed an aerobic copper(II)-mediated phosphorylation of enol acetates with H-phosphonates leading to substituted β-ketophosphonates. The suggested method is versatile and can also be applied to phosphine

Gold extraction at the molecular level using α- and β-cyclodextrins

• Susana Santos Braga

Beilstein J. Org. Chem. 2025, 21, 1116–1125, doi:10.3762/bjoc.21.89

• -precipitation yields from aqueous solutions of α-CD (20 mM) and MAuBr4 (10 mM) (M = Na/K/Rb/Cs) measured at 20 °C by UV–vis spectrophotometry. Right) Structures of the adducts present in co-precipitates with different alkali metals. Reproduced from Z. Liu et al. [40], “Cation-Dependent Gold Recovery with α

Supramolecular assembly of hypervalent iodine macrocycles and alkali metals

• Krishna Pandey,
• Lucas X. Orton,
• Grayson Venus,
• Waseem A. Hussain,
• Toby Woods,
• Lichang Wang and
• Kyle N. Plunkett

Beilstein J. Org. Chem. 2025, 21, 1095–1103, doi:10.3762/bjoc.21.87

• at Urbana-Champaign, Urbana, IL, 61801, United States 10.3762/bjoc.21.87 Abstract This study explores the solution- and solid-state assembly of phenylalanine-based hypervalent iodine macrocycles (HIMs) with lithium and sodium cations. The metal cation binding of HIMs was evaluated by addition of

• pattern of assembly between HIM and metal cation in 2:1 ratio. While association with sodium leads to a polymer-like network, the lithium crystal structure was limited to dimeric assemblies of HIM. In the lithium-coordinating complex, the oxygen–lithium–oxygen bond angle is approximately 98.83

• Buckminster fullerene into long range assembled structures (Figure 1B) [20]. In this contribution, we explored the cation binding abilities of HIMs with first group alkali metals such as lithium and sodium. The phenylalanine-based HIM 1 used in this study was re-synthesized following the previously reported