Synthesis, optical and electrochemical properties of (D–π)₂-type and (D–π)₂Ph-type fluorescent dyes

• Kosuke Takemura,
• Kazuki Ohira,
• Taiki Higashino,
• Keiichi Imato and
• Yousuke Ooyama

Beilstein J. Org. Chem. 2022, 18, 1047–1054, doi:10.3762/bjoc.18.106

• band, but also intense fluorescence emission both in solution and the solid state. Keywords: (D–π)2 structure; fluorescence; fluorescent dyes; photoabsorption; redox properties; Introduction The design and development of a new type of organic fluorescent dyes have been of considerable scientific and

Electrochemical vicinal oxyazidation of α-arylvinyl acetates

• Yi-Lun Li,
• Zhaojiang Shi,
• Tao Shen and
• Ke-Yin Ye

Beilstein J. Org. Chem. 2022, 18, 1026–1031, doi:10.3762/bjoc.18.103

• have reported a manganese dioxide-catalyzed radical azidation of enol acetates to afford the corresponding azidoketones using dioxygen as the oxidant (Scheme 1A) [14]. The adoption of electrosynthesis in green and sustainable redox transformations has been experiencing a dynamic renaissance [15][16][17

Isolation and biosynthesis of daturamycins from Streptomyces sp. KIB-H1544

• Yin Chen,
• Jinqiu Ren,
• Ruimin Yang,
• Jie Li,
• Sheng-Xiong Huang and
• Yijun Yan

Beilstein J. Org. Chem. 2022, 18, 1009–1016, doi:10.3762/bjoc.18.101

• . Diarylcyclopentenones, characteristic constituents of mushrooms [23], were rarely discovered in Streptomyces species. These components exhibit redox activity and are involved in reducing ferric (Fe3+) in the Fenton-based biological decomposition of lignocellulose [24][25]. The biosynthetic pathway of p-terphenyl was

First example of organocatalysis by cathodic N-heterocyclic carbene generation and accumulation using a divided electrochemical flow cell

• Daniele Rocco,
• Ana A. Folgueiras-Amador,
• Richard C. D. Brown and
• Marta Feroci

Beilstein J. Org. Chem. 2022, 18, 979–990, doi:10.3762/bjoc.18.98

• replaces toxic chemical redox reagents and dangerous procedures [22][23][24][25]. At present, electrosynthesis in batch is more widely used and reported in literature, but some disadvantages can be encountered: the need for high concentrations of supporting electrolyte, poor performance for synthesis such

• improved by 10%, but the yield of 2b increased only 2% (Table 2, entry 3). However, in these experiments methyl ester 3a was isolated (24% yield) as byproduct derived from methanol, which passed through the membrane, reacting with the Breslow intermediate through a redox neutral process (Scheme 5) [19]. We

• with the isopropyl alcohol the formation of the ester was only 37%, probably due to steric hindrance. In two cases (Table 3, entries 1 and 2) oxidation byproducts (esters 4a and 4b) were obtained, where the olefinic double bond is preserved. In contrast to the internal redox reactions of cinnamaldehyde

Electrochemical and spectroscopic properties of twisted dibenzo[g,p]chrysene derivatives

• Tomoya Imai,
• Ryuhei Akasaka,
• Naruhiro Yoshida,
• Toru Amaya and
• Tetsuo Iwasawa

Beilstein J. Org. Chem. 2022, 18, 963–971, doi:10.3762/bjoc.18.96

• voltammogram of DBC-H exhibited a reversible, two-step, two-electron redox process, with Eox1 and Eox2 values of 0.34 V and 0.72 V, respectively (Figure 2a). The value of Eox1 is 0.06 V lower than that of MeO-DBC-1 which does not contain isopropyl groups. This is in contrast to MeO-DBC-3, in which four MeO

• DBC-SMe showed a reversible two-electron redox process, with Eox1 and Eox2 values of 0.41 V and 0.88 V, respectively (Figure 2c) [53]. It is interesting to note that DBC-SMe exhibited a higher oxidation potential than DBC-H despite the electron-donating nature due to mesomeric effects based on lone

• pairs of sulfur atoms. In the CV of DBC-Br, a one-electron redox was observed as a reversible process, but a second redox process was not observed (Figure 2d). On the other hand, both the first and second oxidation processes were observed in the SWV of DBC-Br (Eox1 and Eox2 are 0.79 V and 1.15 V

Introducing a new 7-ring fused diindenone-dithieno[3,2-b:2',3'-d]thiophene unit as a promising component for organic semiconductor materials

• Valentin H. K. Fell,
• Joseph Cameron,
• Alexander L. Kanibolotsky,
• Eman J. Hussien and
• Peter J. Skabara

Beilstein J. Org. Chem. 2022, 18, 944–955, doi:10.3762/bjoc.18.94

• compound, EtH-T-DI-DTT, consisting of seven, fused ring systems, with an electron-rich central DTT core, flanked by electron-withdrawing keto groups. Absorption studies in solution and in the solid state show strong aggregation of the molecules in films. EtH-T-DI-DTT shows excellent redox stability with

Cathodic generation of reactive (phenylthio)difluoromethyl species and its reactions: mechanistic aspects and synthetic applications

• Sadanobu Iwase,
• Shinsuke Inagi and
• Toshio Fuchigami

Beilstein J. Org. Chem. 2022, 18, 872–880, doi:10.3762/bjoc.18.88

• are shown in Figure 1. As shown in Figure 1b, a typical reversible redox couple (E1/2red = −1.69 V vs. SSCE) of o-phthalonitrile was clearly observed. A significantly enhanced cathodic peak current was observed after addition of compound 1 to the solution containing o-phthalonitrile while the anodic

• place. Thus, it was found that o-phthalonitrile should work as an electron transfer catalyst, i.e., a redox mediator. On the bases of the cyclic voltammetric measurements, the cathodic reduction of 1 was carried out at a constant potential using o-phthalonitrile as mediator. As shown in Scheme 5, the

Synthesis of α-(perfluoroalkylsulfonyl)propiophenones: a new set of reagents for the light-mediated perfluoroalkylation of aromatics

• Durbis J. Castillo-Pazos,
• Juan D. Lasso and
• Chao-Jun Li

Beilstein J. Org. Chem. 2022, 18, 788–795, doi:10.3762/bjoc.18.79

• synthetic chemistry, we report the synthesis of a series of bench-stable α-(perfluoroalkylsulfonyl)propiophenones. Their application as photocleavable reagents was tested with electron-rich aromatics under metal-free, redox- and pH-neutral conditions to enable late-stage perfluorooctylation

• halogenation reactions or oxidation. For these reasons, it would be ideal to develop an efficient methodology that allows for the generation of perfluoroalkyl radicals in a mild, redox- and pH-neutral manner, without the assistance of external photocatalysts, heavy metal catalysts, or further additives. Thus

• , the expansion of our previously reported propiophenone family of reagents was envisioned as suitable alternative to produce a bench stable, organic soluble, and iodine-free perfluroalkylation source. In 2017, our group developed a metal-free and redox-neutral protocol for the photoinduced alkylation

Menadione: a platform and a target to valuable compounds synthesis

• Acácio S. de Souza,
• Ruan Carlos B. Ribeiro,
• Dora C. S. Costa,
• Fernanda P. Pauli,
• David R. Pinho,
• Matheus G. de Moraes,
• Fernando de C. da Silva,
• Luana da S. M. Forezi and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2022, 18, 381–419, doi:10.3762/bjoc.18.43

• shown a wide range of biological activities of menadione, such as anticancer [15][16][17][18][19][20][21][22], antibacterial [23][24][25][26], antifungal [27][28], antimalarial [29][30][31][32], antichagasic [33], and anthelmintic [34] effects. In these cases, the redox cycle of menadione, followed by

• , followed by oxidation, thus establishing a redox cycle. The main characteristics of the quinones (Q) redox cycle, comprises the one-electron reduction to generate a semiquinone intermediate (SQ) and the two-electron reduction leading to hydroquinone (HQ), in NAD(P)H oxidase-dependent processes [35][36][37

• •−), hydrogen peroxide (H2O2), hydroxyl radical (•OH), and hydroperoxyl radical (•OOH) (Figure 3) [35]. Additionally, the menadione semiquinone radical can participate in another redox cycle, such as, the Fenton reaction, also resulting in the production of hydroxyl and hydroperoxyl radicals (Figure 3) [39][40

Earth-abundant 3d transition metals on the rise in catalysis

• Nikolaos Kaplaneris and
• Lutz Ackermann

Beilstein J. Org. Chem. 2022, 18, 86–88, doi:10.3762/bjoc.18.8

• underdeveloped. This lack of viable catalysis strategies involving 3d transition metals is largely due to a limited knowledge on the working mode of these metal catalysts, which often involve single-electron-transfer-based redox events. As a consequence, there is a strong demand for efficient and reliable

1,2-Naphthoquinone-4-sulfonic acid salts in organic synthesis

• Ruan Carlos B. Ribeiro,
• Patricia G. Ferreira,
• Amanda de A. Borges,
• Luana da S. M. Forezi,
• Fernando de Carvalho da Silva and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2022, 18, 53–69, doi:10.3762/bjoc.18.5

• electrons through a redox cycle promoted by the 1,2- or 1,4-naphthoquinone system. In this cycle, transient reactive oxygen (ROS) and nitrogen (RNS) species are formed as free radicals, peroxides, superoxide anions, radical anions, or dianions. These species generated inside cells accelerate hypoxia and

• addition to the sulfonic acid substitution reaction of position C4 of β-NQS, quinone can be involved in a redox process and, therefore, can be used as an electrode in electrochemical processes. Subsequently, Legua and co-workers [56][57] applied this method to determine amphetamines in urine. Figure 3

• cleaner and form the substitution product at position C4. Fieser and Fieser were the first to study tautomerism between 4-arylamino-1,2-naphthoquinone A and 2-hydroxy-1,4-naphthoquinone-4-arylimine B (Scheme 3C) using the redox potential compared to the pH of the medium. It was observed that

Recent advances and perspectives in ruthenium-catalyzed cyanation reactions

• Thaipparambil Aneeja,
• Cheriya Mukkolakkal Abdulla Afsina,
• Padinjare Veetil Saranya and
• Gopinathan Anilkumar

Beilstein J. Org. Chem. 2022, 18, 37–52, doi:10.3762/bjoc.18.4

• metal. Ruthenium complexes have astonishing characteristics such as high electron transfer ability, low redox potentials, high Lewis acidity, and greater stabilities of the reactive metallic species like oxometals, metallacycles, and metal carbene complexes [27]. The wide availability of highly reactive

DABCO-promoted photocatalytic C–H functionalization of aldehydes

• Bruno Maia da Silva Santos,
• Mariana dos Santos Dupim,
• Cauê Paula de Souza,
• Thiago Messias Cardozo and
• Fernanda Gadini Finelli

Beilstein J. Org. Chem. 2021, 17, 2959–2967, doi:10.3762/bjoc.17.205

• criterias, expanding the range of catalyst choices. This, in turn, can lead to exciting alternatives in terms of functionalizations, selectivities, and can help to illuminate some of the hazy mechanistic aspects of HAT catalysis with bicyclic amines. Redox potentials of representative nitrogenated HAT

Iron-catalyzed domino coupling reactions of π-systems

• Austin Pounder and
• William Tam

Beilstein J. Org. Chem. 2021, 17, 2848–2893, doi:10.3762/bjoc.17.196

• thermal conditions or through the Fe redox cycle, can abstract the aldehydic hydrogen to form the acyl radical 71. Subsequent radical addition to the alkene 68 to form 72 followed by cyclization with the nitrile affords the iminyl radical 73 which can abstract a hydrogen atom to form the more stable imine

• variety of electron-donating and electron-withdrawing groups, though bulky silanes 92 afforded the products in reduced yield. The reaction proceeds through the formation of a silicon-centered radical generated via a Fe redox cycle (vide supra). Sequential attack on the alkenyl π-system followed by radical

Recent advances in the asymmetric phosphoric acid-catalyzed synthesis of axially chiral compounds

• Alemayehu Gashaw Woldegiorgis and
• Xufeng Lin

Beilstein J. Org. Chem. 2021, 17, 2729–2764, doi:10.3762/bjoc.17.185

• poor chemoselectivity [40]. However, the realization of this redox-neutral aryl–aryl cross-coupling is a formidable challenge. Therefore, the discovery of efficient catalysts and ligands to achieve high stereoselectivity is a fundamental issue in catalytic asymmetric synthesis [14]. In this section, we

Visible-light-mediated copper photocatalysis for organic syntheses

• Yajing Zhang,
• Qian Wang,
• Zongsheng Yan,
• Donglai Ma and
• Yuguang Zheng

Beilstein J. Org. Chem. 2021, 17, 2520–2542, doi:10.3762/bjoc.17.169

• ; however, they suffer from relatively poor photostability [14][15][16]. Transition-metal-photoredox catalysts, such as ruthenium and iridium polypyridyl complexes, exhibit high redox potentials, long excited state lifetimes, and strong absorption [17][18][19][20]. However, high cost and their scarcity

• photoredox catalysis of CuI complexes with different ligands were investigated by Reiser’s group [21]. Other studies have since provided more information on the photoredox mechanisms underlying the catalysis of copper complexes [37]. In general, redox-active copper complexes include CuI and CuII complexes

• ). In 2020, Zhang’s group [77] described the photoinduced copper-catalyzed decarboxylative alkynylation of redox-active esters with terminal alkynes. N-Hydroxy-tetrachlorophthalimide (TCNHPI, 36) derived from carboxylic acids was identified as the ideal radical precursor. Under irradiation, the CuI

Synthesis and investigation on optical and electrochemical properties of 2,4-diaryl-9-chloro-5,6,7,8-tetrahydroacridines

• Najeh Tka,
• Mohamed Adnene Hadj Ayed,
• Mourad Ben Braiek,
• Mahjoub Jabli and
• Peter Langer

Beilstein J. Org. Chem. 2021, 17, 2450–2461, doi:10.3762/bjoc.17.162

• reference electrode was calibrated using the ferrocene/ferrocenium (Fc/Fc+) redox system [67], the HOMO and LUMO energies were calculated by using the following equations: Here, VFOC is the potential value of Fc/Fc+ under the same experimental conditions (0.52 V) and 4.8 eV is the HOMO energy value of Fc

Photoredox catalysis in nickel-catalyzed C–H functionalization

• Lusina Mantry,
• Rajaram Maayuri,
• Vikash Kumar and
• Parthasarathy Gandeepan

Beilstein J. Org. Chem. 2021, 17, 2209–2259, doi:10.3762/bjoc.17.143

• developments, which enables a diverse range of previously inaccessible organic transformations in milder reaction conditions [31][32][33][34][35][36][37][38][39][40]. Here, by absorbing visible light, a photocatalyst can function as a single-electron redox mediator through an oxidative or reductive quenching

• cycle (Figure 1), thereby facilitating redox-neutral transformations in the absence of stoichiometric oxidants/reductants. Given the tendency of nickel to mediate the reactions via Ni(0), Ni(I), Ni(II), and Ni(III) intermediates by both giving and accepting a single electron from a photocatalyst or

• . Arylation of α-amino C(sp3)‒H bonds by in situ generated aryl tosylates from phenols. Formylation of aryl chlorides through redox-neutral 2-functionalization of 1,3-dioxolane (13). Photochemical C(sp3)–H arylation via a dual polyoxometalate HAT and nickel catalytic manifold. Photochemical nickel-catalyzed α

On the application of 3d metals for C–H activation toward bioactive compounds: The key step for the synthesis of silver bullets

• Renato L. Carvalho,
• Amanda S. de Miranda,
• Mateus P. Nunes,
• Roberto S. Gomes,
• Guilherme A. M. Jardim and
• Eufrânio N. da Silva Júnior

Beilstein J. Org. Chem. 2021, 17, 1849–1938, doi:10.3762/bjoc.17.126

• involving organochromium species generated from alkyl halides [115][116]. Whereas its toxicity has hindered the use of Cr(VI) in organic synthesis, the less toxic Cr(III) and Cr(II) salts have been exploited as plausible catalysts in organic synthesis [117][118]. A good example is a redox-neutral reaction

• manganese is 3d54s2 with a high redox potential due to the high number of available oxidation states (−3 to +7), allowing the formation of compounds with a coordination number of up to 7 [127]. These properties associated with a low toxicity and low cost make manganese a metal with great potential in

• , operating under mild conditions without the need of directing groups, using traceless electrons as sole redox reagents, presenting high scope and chemoselectivity. The robustness of the reaction was proved by the late-stage modification of pharmaceutically relevant compounds by promoting the azidation of a

Natural products in the predatory defence of the filamentous fungal pathogen Aspergillus fumigatus

• Jana M. Boysen,
• Nauman Saeed and
• Falk Hillmann

Beilstein J. Org. Chem. 2021, 17, 1814–1827, doi:10.3762/bjoc.17.124

• the GT concentration at sub-lethal levels via redox cycling and S-methylation of active disulfides in GT, respectively [117][118]. Furthermore, in terms of exogenous factors, not only GT itself but several other biotic and abiotic factors, including neutrophilic granulocytes, media composition, pH

• , temperature and aeration, are known to regulate gliotoxin biosynthesis [115][119][120]. The biological activity of ETP’s like gliotoxin is mediated by the active disulfide bridge that targets vulnerable thiols or catalyses oxidative burst formation via redox cycling [78]. In previous studies, these cytotoxic

Chemical approaches to discover the full potential of peptide nucleic acids in biomedical applications

• Nikita Brodyagin,
• Martins Katkevics,
• Venubabu Kotikam,
• Christopher A. Ryan and
• Eriks Rozners

Beilstein J. Org. Chem. 2021, 17, 1641–1688, doi:10.3762/bjoc.17.116

Recent advances in the application of isoindigo derivatives in materials chemistry

• Andrei V. Bogdanov and
• Vladimir F. Mironov

Beilstein J. Org. Chem. 2021, 17, 1533–1564, doi:10.3762/bjoc.17.111

• trinitrotoluene) in solution was demonstrated (Scheme 30) [110][111]. Miscellaneous applications Taking into account the high thermal, atmospheric, mechanical, and redox stability of isoindigo polymers, various scientific groups focused their studies on the development of new directions for the practical

• , such as staining efficiency (362 cm2⋅C−1 at 1050 nm), fast switching time (0.5 s), high optical contrast (59% at 1500 nm), and redox stability (<8% after 4000 cycles). Poly(isoindigothiophene) 65 containing sulfonate groups in the side chain was used as an anionic photoactive polyelectrolyte in a

• , the first work on combining polyaromatic acceptor and heterocyclic donor fragments in one macromolecule on the isoindigo platform showed the possibility of designing one-component nonfullerene solar cells. The high stability of polymeric isoindigo in air, at elevated temperature, under redox

Icilio Guareschi and his amazing “1897 reaction”

• Gian Cesare Tron,
• Alberto Minassi,
• Giovanni Sorba,
• Mara Fausone and
• Giovanni Appendino

Beilstein J. Org. Chem. 2021, 17, 1335–1351, doi:10.3762/bjoc.17.93

• ”, formally an internal redox reaction where the heterocyclic system is oxidatively aromatized and one of the substituents at C-4 reductively lost as a hydrocarbon. The reaction involves the treatment of a ketone with a solution of ethylcyanoacetate in ethanolic ammonia [7]. A precipitate of the ammonium salt

• terms of overall redox transformation, the reaction formally “hydrolyses” a ketone into a hydrocarbon and a carboxylic acid, and the mechanism remained a black box for over a century, being eventually clarified only in 2007 by a team of British and Russian chemists [8]. One important starting

Photoinduced post-modification of graphitic carbon nitride-embedded hydrogels: synthesis of 'hydrophobic hydrogels' and pore substructuring

• Cansu Esen and
• Baris Kumru

Beilstein J. Org. Chem. 2021, 17, 1323–1334, doi:10.3762/bjoc.17.92

• novelty. Here, a metal-free semiconductor graphitic carbon nitride (g-CN)-embedded hydrogel as an initial network was synthesized via redox-couple initiation under dark conditions. Post-photomodification of so-formed hydrogel, thanks to the photoactivity of the embedded g-CN nanosheets, was exemplified in

• yellow powder was ultrasonicated in water to obtain a g-CN aqueous colloidal dispersion. The freshly prepared CM/water colloidal dispersion was mixed with water-soluble monomer (N,N-dimethylacrylamide, DMA) and crosslinker (N,N’-methylenebisacrylamide, MBA) followed by the addition of the redox couple

• , ascorbic acid/hydrogen peroxide, respectively. The mixture was immediately placed in a Petri dish to complete the gelation via free radical polymerization under dark conditions. After 3 hours, the resulting hydrogel was purified with water to remove the unreacted species (monomers and redox mediators

Synthesis of 10-O-aryl-substituted berberine derivatives by Chan–Evans–Lam coupling and investigation of their DNA-binding properties

• Peter Jonas Wickhorst,
• Mathilda Blachnik,
• Denisa Lagumdzija and
• Heiko Ihmels

Beilstein J. Org. Chem. 2021, 17, 991–1000, doi:10.3762/bjoc.17.81

• berberrubine (1b), which has been shown to give no products in an Ullmann reaction [31]. Furthermore, the sensitivity of the isoquinolinium unit towards alkaline conditions and redox-active transition metal ions, especially under aerobic conditions, may also cause the low yields [35][36][37]. Unfortunately