Recent advances in organocatalytic atroposelective reactions

• Henrich Szabados and
• Radovan Šebesta

Beilstein J. Org. Chem. 2025, 21, 55–121, doi:10.3762/bjoc.21.6

Surprising acidity for the methylene of 1,3-indenocorannulenes?

• Shi Liu,
• Märt Lõkov,
• Sofja Tshepelevitsh,
• Ivo Leito,
• Kim K. Baldridge and
• Jay S. Siegel

Beilstein J. Org. Chem. 2024, 20, 3144–3150, doi:10.3762/bjoc.20.260

• is more nuanced [10][11]. Subsequently, literature and computational examples reveal a leitmotif for CpH-PAH-based redox-active carbon-rich materials. Results and Discussion From competitive titrations against 9-C6F5-fluorene (pKa = 28.14 in CH3CN) [12][13] and (4-Me-C6F4)(C6H5)CHCN (pKa = 26.98 in

• pentabenzocorannulene would produce air-stable radical and ionic PAHs, and that coupling such fragments would lead to stable redox-active carbon sheets. Conclusion In conclusion, the “surprise” in the surprising pKa for BIC and FIC was in our expectation of the deprotonated forms as poorly delocalized fluorenyl anions

• unforeseen new material designs (e.g., redox-active electrooptical materials). Methods pKa measurements in acetonitrile The experimental setup and methodology for the pKa determination of BFC and FIC in acetonitrile was essentially the same as described in detail in previous papers [12][13]. A brief

Advances in the use of metal-free tetrapyrrolic macrocycles as catalysts

• Mandeep K. Chahal

Beilstein J. Org. Chem. 2024, 20, 3085–3112, doi:10.3762/bjoc.20.257

• . Changes in the reduction or oxidation state can alter redox behavior, thereby affecting catalytic activity. For example, it has been reported that 2,3,5,7,8,10,12,13,15,17,18,20-dodecasubstituted free-base porphyrins and their mono/diprotonated derivatives are highly distorted with a good access to the

• photocatalysts. The results demonstrated that these substituents significantly influenced the redox properties of the porphyrins, yielding up to 86% with the electron-poor meso-tetrakis(pentafluorophenyl)porphyrin (67), compared to H2TPP and other electron-rich systems. This finding indicated that fine-tuning

• batteries, due to the ease of their structural modification, rich redox chemistry, and robust coordination M–N4 environment [100][101][102][103][104][105]. The key processes employed in energy transfer and storage are the oxygen reduction reaction (ORR), hydrogen evolution reaction (HER), and oxygen

Cyclodextrin-based rotaxanes for polymer materials: challenge on simultaneous realization of inexpensive production and defined structures

• Yosuke Akae

Beilstein J. Org. Chem. 2024, 20, 3026–3049, doi:10.3762/bjoc.20.252

• )rotaxane framework The rotaxane framework is often deployed as a molecular device in which the positional relationship between the axle and wheel is controlled by external stimuli [14][32]. Acid–base, photoisomerization, redox, ion recognition, solvent polarity, or heating treatment is generally used for

• stilbene has been generally used to control the position of CD in the rotaxane structure [14][15]. In addition to the photoisomerization–based system, redox-based structural control was reported by Stoddart and co-workers in 2008 using α-CD-based [2]rotaxane bearing a dumbbell molecule comprising

Advances in radical peroxidation with hydroperoxides

• Oleg V. Bityukov,
• Pavel Yu. Serdyuchenko,
• Andrey S. Kirillov,
• Gennady I. Nikishin,
• Vera A. Vil’ and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2024, 20, 2959–3006, doi:10.3762/bjoc.20.249

• photoredox catalysis [26][27][28]. These methods allow selectivity to be controlled despite the presence of the complex cocktail of radical species generated by hydroperoxides under redox or homolysis conditions. The main challenge in selective radical peroxidation is the wide range of possible pathways

• involving radical intermediates from hydroperoxides under redox conditions (Scheme 3). The reactivity of O-centered radicals is less predictable and more diverse depending on radical structure and substrate pattern than the chemistry of C-centered radicals [29][30]. Generally, peroxy radicals have a

• -scission [31][32], which can lead to side reactions. Some aspects of the rich metal–peroxide redox chemistry have been discussed in previous reviews [33]. Specifically, the radical functionalization of C–C bonds accessed through the transition metal-mediated reduction of organic peroxides has been covered

Synthesis of fluorinated acid-functionalized, electron-rich nickel porphyrins

• Mike Brockmann,
• Jonas Lobbel,
• Lara Unterriker and
• Rainer Herges

Beilstein J. Org. Chem. 2024, 20, 2954–2958, doi:10.3762/bjoc.20.248

• to serve as a proton source for redox reactions at the metal. 3. The electronic properties of the porphyrin, especially the low oxidation potential, should not be increased. We have chosen four-fold meso-3,4,5-trimethoxyphenyl-substituted Ni porphyrin as the electron-rich system, however, the post

The charge transport properties of dicyanomethylene-functionalised violanthrone derivatives

• Sondos A. J. Almahmoud,
• Joseph Cameron,
• Dylan Wilkinson,
• Michele Cariello,
• Claire Wilson,
• Alan A. Wiles,
• Peter J. Skabara and
• Graeme Cooke

Beilstein J. Org. Chem. 2024, 20, 2921–2930, doi:10.3762/bjoc.20.244

• reversible oxidation waves as shown from the CV data (Figure 6 and Table 1). This reversibility is crucial for the regeneration of dyes following redox processes. The compounds display ionisation energies (IEs) of −5.38 eV, −5.34 eV, and −5.40 eV for 3a, 3b, and 3c, respectively, with electron affinities

N-Glycosides of indigo, indirubin, and isoindigo: blue, red, and yellow sugars and their cancerostatic activity

• Peter Langer

Beilstein J. Org. Chem. 2024, 20, 2840–2869, doi:10.3762/bjoc.20.240

• application of the Mukaiyama redox condensation using N-iodosuccinic imide (NIS) afforded 10b. Hydrogenation resulted in defunctionalization to give 10c. Transformation of OH-4 to a triflate and subsequent reaction with sodium azide afforded gluco-configured product 10d. The latter was transformed to

A review of recent advances in electrochemical and photoelectrochemical late-stage functionalization classified by anodic oxidation, cathodic reduction, and paired electrolysis

• Nian Li,
• Ruzal Sitdikov,
• Ajit Prabhakar Kale,
• Joost Steverlynck,
• Bo Li and
• Magnus Rueping

Beilstein J. Org. Chem. 2024, 20, 2500–2566, doi:10.3762/bjoc.20.214

• orbital during enolate formation, thus providing mild redox conditions. After anodic oxidation, a carbon-centered radical at the α-position is formed, which undergoes stereocontrolled C–C-bond formation with the silyl ether, forming a trimethylsilyl (TMS)-ketyl radical. A second anodic one-electron

• ) as the redox mediator, this method showed excellent tolerance across various arenes and alkenes. The selective LSF of biorelevant complex molecules demonstrated significant potential for drug exploration (Scheme 42a). One year later, the same group disclosed the dehydrogenative cross-coupling of two

Synthesis, electrochemical properties, and antioxidant activity of sterically hindered catechols with 1,3,4-oxadiazole, 1,2,4-triazole, thiazole or pyridine fragments

• Daria A. Burmistrova,
• Andrey Galustyan,
• Nadezhda P. Pomortseva,
• Kristina D. Pashaeva,
• Maxim V. Arsenyev,
• Oleg P. Demidov,
• Mikhail A. Kiskin,
• Andrey I. Poddel’sky,
• Nadezhda T. Berberova and
• Ivan V. Smolyaninov

Beilstein J. Org. Chem. 2024, 20, 2378–2391, doi:10.3762/bjoc.20.202

• : antioxidant activity; catechol thioethers; heterocycles; redox-transformations; thiones; Introduction Synthetic derivatives of polyphenols, in particular catechol (hydroquinone), represent a promising group of pharmacologically active substances [1][2]. Catechol-containing compounds demonstrate

• heteroatoms (nitrogen, sulfur, selenium, tellurium, etc.) as well as redox-active functional groups allows one to vary significantly the biological activity of such compounds. Heterocyclic molecular blocks are widely used in medicinal chemistry [12]. Thiazole, oxadiazole, triazole, imidazole, and other

• ) < 1,3,4-oxadiazole derivatives (1.37–1.39 V). The redox properties of catechols 1–9 were studied by cyclic voltammetry (CV) (Table 1). In the anodic area, the electrochemical profile for catechol thioethers 1–5 represents two successive irreversible oxidative stages. The first two-electron peak is

Improved deconvolution of natural products’ protein targets using diagnostic ions from chemical proteomics linkers

• Andreas Wiest and
• Pavel Kielkowski

Beilstein J. Org. Chem. 2024, 20, 2323–2341, doi:10.3762/bjoc.20.199

• acid, base, or redox-labile parts of the linker [52]. Most recently, Wozniak et al. mapped the binding sites of a large small molecules library, which were equipped with a photo-crosslinker [110]. The study used the acid-cleavable dialkoxydiphenylsilane (DADPS) linker to release the probe–peptide

Hydrogen-bond activation enables aziridination of unactivated olefins with simple iminoiodinanes

• Phong Thai,
• Lauv Patel,
• Diyasha Manna and
• David C. Powers

Beilstein J. Org. Chem. 2024, 20, 2305–2312, doi:10.3762/bjoc.20.197

• of the sulfonamide resulted in O–H proton signal of HFIP being at 5.64 ppm with FWHM = 11.3 Hz. Second, to evaluate the impact of HFIP on the redox chemistry of PhINTs, we collected cyclic voltammograms (CVs) of iminoiodinane 2c in MeCN in the presence of varying HFIP increments (Scheme 4b). The CV

Synthesis and reactivity of the di(9-anthryl)methyl radical

• Tomohiko Nishiuchi,
• Kazuma Takahashi,
• Yuta Makihara and
• Takashi Kubo

Beilstein J. Org. Chem. 2024, 20, 2254–2260, doi:10.3762/bjoc.20.193

• spectroscopy under ambient conditions. The CV of DAntM species showed a reversible wave at E1/2 = −0.20 V (V vs Fc/Fc+) (Figure 5a) [39]. This redox potential is close to that of TAntM radical and cation [17]. Additionally, at a scan rate of 0.1 V s−1, the current peak intensity on the anodic side (from

• radical to cation) was significantly lower than that on the cathodic side (from cation to radical), resulting in an irreversible redox wave. However, by increasing the scan rate, the current peak intensity on the anodic side gradually increased, and the difference in current intensity between the anodic

• and cathodic sides became smaller, resulting in a reversible redox wave (Figure 5b). This indicates that the generated DAntM radical rapidly decomposes during the CV measurement, leading to the irreversible redox wave at slow scan rate. The UV–vis spectra of the DAntM radical and cation were shown in

Natural resorcylic lactones derived from alternariol

• Joachim Podlech

Beilstein J. Org. Chem. 2024, 20, 2171–2207, doi:10.3762/bjoc.20.187

• determined by NMR spectroscopy and unambiguously confirmed by total syntheses [44][177]. It showed cytotoxic activity against SW1116 cells with an IC50 value of 12 μg/mL [168]. Chlorinated alternariol derivatives (Figure 9) together with the respective redox-modified natural products (Figure 20, vide infra

Efficacy of radical reactions of isocyanides with heteroatom radicals in organic synthesis

• Akiya Ogawa and
• Yuki Yamamoto

Beilstein J. Org. Chem. 2024, 20, 2114–2128, doi:10.3762/bjoc.20.182

• –heteroatom bonded compound (E–E) upon heating or photoirradiation. Similarly, E• adds to 1 to form 2, which undergoes atom (or group)-transfer from E–E to give the 1,1-addition product 4 with regeneration of E• [17][18]. In method 3, the photoinduced redox reaction of a heteroatom compound takes place using

Multicomponent syntheses of pyrazoles via (3 + 2)-cyclocondensation and (3 + 2)-cycloaddition key steps

• Ignaz Betcke,
• Alissa C. Götzinger,
• Maryna M. Kornet and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2024, 20, 2024–2077, doi:10.3762/bjoc.20.178

• . In cases where the α,β-unsaturated carbonyl compounds contain a heteroatom in the β-position, aromatization is triggered by elimination under redox-neutral conditions. Tasch et al. successfully coupled aryl halides with α-bromocinnamaldehyde (51) using a Masuda borylation Suzuki cross-coupling (MBSC

Harnessing the versatility of hydrazones through electrosynthetic oxidative transformations

• Aurélie Claraz

Beilstein J. Org. Chem. 2024, 20, 1988–2004, doi:10.3762/bjoc.20.175

• drive oxidative and reductive processes precludes the reliance on toxic or dangerous redox reagents [32]. The explosive renewal of interest in this technology and the resulting recent achievements have brought it at the forefront of organic synthesis. Electrooxidative transformations of hydrazones offer

• -diphenylethylene proceeded with similar efficiency, thereby excluding any radical pathway. As such, it was proposed that the catalytic electrooxidation of iodide (ENH4I = 0.41 V and 0.75 V vs Ag/AgCl in dimethylacetamide for I−/I3− and I3−/I2 redox couples) into iodine provided a green and mild tool to in situ

• , imidazole, pyrazole and triazoles (Scheme 23) [72]. Cyclic voltammetry studies confirmed that the azoles were redox inactive in the scan window while benzaldehyde-derived morpholino hydrazone could be readily oxidized at 1.18 V vs SCE in CH3CN supporting the route (a) of the general mechanism in Scheme 20

Radical reactivity of antiaromatic Ni(II) norcorroles with azo radical initiators

• Siham Asyiqin Shafie,
• Ryo Nozawa,
• Hideaki Takano and
• Hiroshi Shinokubo

Beilstein J. Org. Chem. 2024, 20, 1967–1972, doi:10.3762/bjoc.20.172

• physical properties, such as reversible redox properties [4][5] and stacked-ring aromaticity [6][7][8][9][10]. While Ni(II) norcorroles are stable under ambient conditions despite the distinct 16π-antiaromaticity, they show unique reactivities with various reagents due to the high-lying HOMO and low-lying

Novel oxidative routes to N-arylpyridoindazolium salts

• Oleg A. Levitskiy,
• Yuri K. Grishin and
• Tatiana V. Magdesieva

Beilstein J. Org. Chem. 2024, 20, 1906–1913, doi:10.3762/bjoc.20.166

• . Voltammetry studies of the electrochemical behavior of the novel pyridoindazolium salts and the starting diarylamines were performed confirming a possibility for their reversible redox interconversion. Results and Discussion Chemical oxidation Three previously reported ortho-pyridine-substituted diarylamines

• testing confirmed that oxidation of the pyridyl-containing amines results in the intramolecular heterocyclization yielding pyridoindazolium salts. The reduction of N-arylpyridoindazoliums in the presence of a source of protons restores the starting diarylamines. Redox-interconversion between diarylamines

• into the reaction mixture (Figure 4a,b). Notably, the effect was more pronounced in the presence of lutidine, especially in the case of TEMPO. The difference between the oxidation potential of A3 and the potential of the TEMPO/TEMPO+ redox couple is rather significant (ca. 0.35 V); the base additives

A facile three-component route to powerful 5-aryldeazaalloxazine photocatalysts

• Ivana Weisheitelová,
• Radek Cibulka,
• Marek Sikorski and
• Tetiana Pavlovska

Beilstein J. Org. Chem. 2024, 20, 1831–1838, doi:10.3762/bjoc.20.161

• of applications in medicinal chemistry, chemosensors, polymers and catalysis [1][2][3][4][5][6][7][8]. Among them, flavins (Fl) are essential redox-active natural compounds that act as enzyme cofactors in numerous biochemical processes [9]. Structurally related to flavins are isomeric alloxazines

• of photocatalysts by tuning their redox and photophysical properties. Thus, we successfully developed a one-pot, three-component synthetic method with those substituents in 5-aryldeazaflavins 1 on the deazaisoalloxazine core or on the phenyl ring by condensation of N-substituted anilines, aromatic

Synthesis of polycyclic aromatic quinones by continuous flow electrochemical oxidation: anodic methoxylation of polycyclic aromatic phenols (PAPs)

• Hiwot M. Tiruye,
• Solon Economopoulos and
• Kåre B. Jørgensen

Beilstein J. Org. Chem. 2024, 20, 1746–1757, doi:10.3762/bjoc.20.153

• after removal of solvents from the reaction mixture. Thus, Et4NOTs can easily be recycled and reused for a greener reaction. Voltammetric studies To investigate their redox behaviour, PAPs 1a,b (Figure 1A), 3a–c (Figure 1C), and 6a–c (Figure 1E) were scanned between +2.2 V and −1.5 V. All compounds

• radical and a naphthyloxy cation leading to the formation of 5. Our CV studies exhibit oxidation peaks, which seem in line with what to expect for an electrochemical oxidation of PAPs. Through the cyclic voltammetry experiments for the investigation of the redox behavior of the PAPs, an estimation of

• hexafluorophosphate ([NBu4] [PF6]) solution in acetonitrile. The solvent was dried and degassed using N2 prior to each experiment. All experiments were conducted at room temperature. All redox potentials were calibrated against ferrocene/ferrocenium (Fc/Fc+) redox couple. Cyclic voltammograms of PAPs first scan at

New triazinephosphonate dopants for Nafion proton exchange membranes (PEM)

• Fátima C. Teixeira,
• António P. S. Teixeira and
• C. M. Rangel

Beilstein J. Org. Chem. 2024, 20, 1623–1634, doi:10.3762/bjoc.20.145

• combinatorial chemistry [35], in analytical chemistry, in electrochemical redox processes, in crystal engineering, and as fluorescent, light emitting, corrosion inhibitors or several other materials [36][37][38][39][40][41][42]. The most used triazine is 1,3,5-triazine (or s-triazine) that can provide

Tetrabutylammonium iodide-catalyzed oxidative α-azidation of β-ketocarbonyl compounds using sodium azide

• Christopher Mairhofer,
• David Naderer and
• Mario Waser

Beilstein J. Org. Chem. 2024, 20, 1510–1517, doi:10.3762/bjoc.20.135

• ][25][26][27][28][29][30][31]. Such oxidative coupling strategies of two inherently nucleophilic species allow for the direct utilization of simple starting materials in an efficient manner and especially the use of quaternary ammonium iodides as redox active catalysts has emerged as a powerful

Electrophotochemical metal-catalyzed synthesis of alkylnitriles from simple aliphatic carboxylic acids

• Yukang Wang,
• Yan Yao and
• Niankai Fu

Beilstein J. Org. Chem. 2024, 20, 1497–1503, doi:10.3762/bjoc.20.133

• ][18]. Owing to the prevalence of aliphatic carboxylic acids in biomass and natural products, decarboxylative cyanation represents one of the most straightforward and attractive approaches to accessing alkylnitriles [19][20]. As an elegant example, Barton demonstrated the application of redox-active

• plate as the cathode, was electrolyzed with a cell potential of 2.3 V (corresponding to an initial anodic potential of 0.10 V versus the ferrocenium ion/ferrocene redox couple) under the irradiation of 400 nm light-emitting diodes (LEDs). Through systematic optimization, we found that the use of readily

Generation of alkyl and acyl radicals by visible-light photoredox catalysis: direct activation of C–O bonds in organic transformations

• Mithu Roy,
• Bitan Sardar,
• Itu Mallick and
• Dipankar Srimani

Beilstein J. Org. Chem. 2024, 20, 1348–1375, doi:10.3762/bjoc.20.119

• becomes significant. C(sp3)–O bonds are ubiquitous in nature and can be easily found in biochemical feedstocks, such as alcohols and acids. On the other hand, alcohols and acids are easily accessible. Although the starting materials are abundant, the C–O bond strength and the high redox potential impede

• , such as iridium complexes or organic dyes, and activating agents, including dimethyl dicarbonate (DMDC) and PPh3. Redox-active esters are created when activating agents and carboxylic acids react. These esters can then be reduced using a photoredox catalyst to produce the acyl radical. In 2019, Doyle

• interesting. However, direct C–O bond activation of alcohols by visible light is limited due to the large redox potential and the high C–O bond energy. As such, the conversion of alcohols to redox-active groups is necessary to tackle this issue. In this section, we will discuss various types of