Annulation of a 1,3-dithiole ring to a sterically hindered o-quinone core. Novel ditopic redox-active ligands

• Sergey V. Norkov,
• Anton V. Cherkasov,
• Andrey S. Shavyrin,
• Maxim V. Arsenyev,
• Viacheslav A. Kuropatov and
• Vladimir K. Cherkasov

Beilstein J. Org. Chem. 2021, 17, 273–282, doi:10.3762/bjoc.17.26

• State University, 23 Gagarin Ave, 603950, Nizhny Novgorod, Russia 10.3762/bjoc.17.26 Abstract The fused 1,3-dithiole spacer seems to be very suitable for the functionalization of sterically hindered o-quinones with additional groups capable of coordination of metal ions and/or possessing a redox

• ligand; 1,3-dithiole; ditopic ligand; o-quinone; thiete; Introduction There are a number of methods which may be used for the synthesis of new o-quinones in order to vary their redox properties and coordination abilities. The key features of o-quinones are redox activity as well as chelating

• coordination ability. The redox state of o-quinone (semiquinone or catechol) could be changed both as free species or when it is coordinated to a metal ion as a ligand. Thus, the redox isomerism phenomenon was reported for o-quinone complexes with both transition and non-transition metals [1][2][3]. The

Insight into functionalized-macrocycles-guided supramolecular photocatalysis

• Minzan Zuo,
• Krishnasamy Velmurugan,
• Kaiya Wang,
• Xueqi Tian and
• Xiao-Yu Hu

Beilstein J. Org. Chem. 2021, 17, 139–155, doi:10.3762/bjoc.17.15

• macrocycle has inherent chromophores that can function as photosensitizers, the efficiency of the energy transfer will be higher and the systems will be simplified. 3) Other kinds of macrocycle-based catalysis need to be explored, such as esterification, polymerization, redox reaction, etc. 4) Hyperbranched

Synthesis of tetrafluorinated piperidines from nitrones via a visible-light-promoted annelation reaction

• Vyacheslav I. Supranovich,
• Igor A. Dmitriev and
• Alexander D. Dilman

Beilstein J. Org. Chem. 2020, 16, 3104–3108, doi:10.3762/bjoc.16.260

• from nitrones and a fluorinated building block is described. The annelation is based on a sequence of visible-light-promoted redox processes and a substitution reaction, and involves the cleavage of the N–O bond. The construction of tetrafluorinated piperidines from nitrones. The scope of the

Controlled decomposition of SF₆ by electrochemical reduction

• Sébastien Bouvet,
• Bruce Pégot,
• Stéphane Sengmany,
• Erwan Le Gall,
• Eric Léonel,
• Anne-Marie Goncalves and
• Emmanuel Magnier

Beilstein J. Org. Chem. 2020, 16, 2948–2953, doi:10.3762/bjoc.16.244

• +/Fc. The exact number of electrons for the full consumption of sulfur hexafluoride was determined and this gas further quantitatively transformed into environmentally benign fluoride anion and sulfur by electrochemical reduction. Keywords: electroreduction; fluoride anion; redox potential; sulfur

• , in accordance with the following relation [26]: To the half limiting current (id/2) can be associated the half wave potential noted E1/2. For reversible electrons exchanged at the interface electrode/electrolyte, the half wave potential can be assimilated to the reversible formal potential redox

• on SF6 concentration. From the voltamogram, the half wave potential of SF6 reduction is deduced and corresponds to −2.17 V vs Fc+/Fc (Figure 1). To the best of our knowledge, this was the first determination of the redox potential of sulfur hexafluoride. Pleasingly, this value was compatible with the

Ultrasound-assisted Strecker synthesis of novel 2-(hetero)aryl-2-(arylamino)acetonitrile derivatives

• Emese Gal,
• Luiza Gaina,
• Hermina Petkes,
• Alexandra Pop,
• Castelia Cristea,
• Gabriel Barta,
• Dan Cristian Vodnar and
• Luminiţa Silaghi-Dumitrescu

Beilstein J. Org. Chem. 2020, 16, 2929–2936, doi:10.3762/bjoc.16.242

• frequencies between 20 and 100 kHz were reported in the literature as optimal to enhance the nucleation and fragmentation rates, but the exact optimal frequency is probably reactor and system specific [8]. The exciting properties of the heterocyclic phenothiazine core displaying tunable chemical, redox

• ferrocene unit displays a remarkably reversible one-electron oxidation behavior offering interesting fields of applications for its derivatives as redox mediators in sensor applications [10]. Medicinal applications of ferrocene derivatives grafted on different pharmacophoric units greatly benefit from the

Synthesis and characterization of S,N-heterotetracenes

• Astrid Vogt,
• Florian Henne,
• Christoph Wetzel,
• Elena Mena-Osteritz and
• Peter Bäuerle

Beilstein J. Org. Chem. 2020, 16, 2636–2644, doi:10.3762/bjoc.16.214

• precursors and amines [11][12], the series of S,N-heteroacenes has been systematically extended from pentamer SN5 [13][14] up to a stable and still soluble S,N-heterotridecacene SN13 [7][15][16][17]. Correlation of, e.g., absorption or redox potentials vs conjugated chain length led to interesting structure

• are shifted down-field (Hα 7.67, Hß 7.49 ppm) compared to SN4 13. MALDI–HRMS of all synthesized S,N-heteroacenes showed only a single peak for the molecular ions accounting for their purity. Optical and redox properties of S,N-heteroacenes 9, 13, 19, 22, and 33 in comparison to tetrathienoacene (TTA

• planar and conformationally restricted systems [48]. In order to get information about the redox properties and energetics of the frontier orbitals, the S,N-heteroacenes were studied by cyclic voltammetry and all potentials were referenced against the ferrocene/ferricenium couple (Table 1). In the series

Thermodynamic and electrochemical study of tailor-made crown ethers for redox-switchable (pseudo)rotaxanes

• Henrik Hupatz,
• Marius Gaedke,
• Hendrik V. Schröder,
• Julia Beerhues,
• Arto Valkonen,
• Fabian Klautzsch,
• Sebastian Müller,
• Felix Witte,
• Kari Rissanen,
• Biprajit Sarkar and
• Christoph A. Schalley

Beilstein J. Org. Chem. 2020, 16, 2576–2588, doi:10.3762/bjoc.16.209

• synthetic molecular machines. Developing switchable and specifically designed crown ethers enables the implementation of function into molecular assemblies. Seven tailor-made redox-active crown ethers incorporating tetrathiafulvalene (TTF) or naphthalene diimide (NDI) as redox-switchable building blocks are

• described with regard to their potential to form redox-switchable rotaxanes. A combination of isothermal titration calorimetry and voltammetric techniques reveals correlations between the binding energies and redox-switching properties of the corresponding pseudorotaxanes with secondary ammonium ions. For

• corresponding free macrocycle. The detailed understanding of the thermodynamic and electrochemical properties of the tailor-made crown ethers lays the foundation for the construction of new types of molecular redox switches with emergent properties. Keywords: crown ether; isothermal titration calorimetry

Palladium nanoparticles supported on chitin-based nanomaterials as heterogeneous catalysts for the Heck coupling reaction

• Tony Jin,
• Malickah Hicks,
• Davis Kurdyla,
• Sabahudin Hrapovic,
• Edmond Lam and
• Audrey Moores

Beilstein J. Org. Chem. 2020, 16, 2477–2483, doi:10.3762/bjoc.16.201

• FTIR and PXRD showed little to no structural change to the biomaterials after metal deposition. Heck coupling results demonstrate the importance of using ChNCs as opposed to ChsNCs in order to control the redox chemistry of Pd, with full product yield in relatively mild conditions using PdNP@ChNC. TEM

Recent developments in enantioselective photocatalysis

• Callum Prentice,
• James Morrisson,
• Andrew D. Smith and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2020, 16, 2363–2441, doi:10.3762/bjoc.16.197

• , which are photocatalytically generated in situ from redox-active esters 242 (Scheme 38) [99]. The mechanism advanced by Wang et al. proposes that 241 acts as a sacrificial reductant to generate the reduced photocatalyst, which can then reduce 242 in a second SET step to give α-amino radical 242• after

Synthetic approaches to bowl-shaped π-conjugated sumanene and its congeners

• Shakeel Alvi and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 2212–2259, doi:10.3762/bjoc.16.186

• potential applications ranging from the chemistry perspective to materials science and technology [1][2][3][4]. As we know that bowled (curved) surfaces are universal in nature for example our planets as well as atomic orbitals possess the curvature which generally affects the charge-transport, redox, self

• furnish compound 132 (Scheme 34). Since polyanilines are interesting π-conjugated polymers that contain characteristic conductivity by acid doping, environmental stability, optical and redox properties. Therefore, bridging of oligoaniline as a spacer between the functional units can lead toward the

Photosensitized direct C–H fluorination and trifluoromethylation in organic synthesis

• Shahboz Yakubov and
• Joshua P. Barham

Beilstein J. Org. Chem. 2020, 16, 2151–2192, doi:10.3762/bjoc.16.183

• ). An unfortunate consequence of this is that there are many organic molecules with redox potentials that lie beyond the range of those of the excited photocatalyst [87]. The transiently generated (ultralow concentration of) the excited-state catalyst does not persist long enough even for slightly

• endergonic SET, so no reaction occurs. Moreover, C–H bonds are not redox-active. To circumvent those issues, SET can be leveraged to generate an HAT agent to activate C–H bonds. For the purposes of this review, we label this reaction class involving redox processes as PRC. ii) Photochemical reactions in

• can function as an energy donor to activate the relatively lower triplet energy of the energy acceptor through an overall PS TTET process [91][92][93][94][95][96][97][98][99][100]. In contrast to PRC, the mechanism of TTET occurs in a way that does not depend on the redox potential of the molecules or

Azo-dimethylaminopyridine-functionalized Ni(II)-porphyrin as a photoswitchable nucleophilic catalyst

• Jannis Ludwig,
• Julian Helberg,
• Hendrik Zipse and
• Rainer Herges

Beilstein J. Org. Chem. 2020, 16, 2119–2126, doi:10.3762/bjoc.16.179

• following several approaches using a variety of photochromic systems. Feringa et al. recently published a review including systems based on double bond isomerizations [1]. An earlier review from the same group summarized light and redox responsive catalytic systems including azobenzenes, diarylethenes

Design, synthesis and application of carbazole macrocycles in anion sensors

• Alo Rüütel,
• Ville Yrjänä,
• Sandip A. Kadam,
• Indrek Saar,
• Mihkel Ilisson,
• Astrid Darnell,
• Kristjan Haav,
• Tõiv Haljasorg,
• Lauri Toom,
• Johan Bobacka and
• Ivo Leito

Beilstein J. Org. Chem. 2020, 16, 1901–1914, doi:10.3762/bjoc.16.157

• sensor prototypes. EIS measurements were used primarily to ensure that the solid contact had a sufficiently large redox capacitance and to compare the influence of the ionophore upon the spectra, if any could be observed. Examples of the recorded impedance spectra are shown in Figure 7. The membrane bulk

• frequencies showed that the solid contacts had large redox capacitances [33]. The low-frequency regions showed some differences between the different membranes and MC005 stood out due to the presence of a partial semicircle that was absent in all other membranes. The low-frequency region is associated with

When metal-catalyzed C–H functionalization meets visible-light photocatalysis

• Lucas Guillemard and
• Joanna Wencel-Delord

Beilstein J. Org. Chem. 2020, 16, 1754–1804, doi:10.3762/bjoc.16.147

• selecting judiciously a PC with adequate redox potentials, the ground state of the latter could be regenerated by means of a mild and abundant oxidant such as molecular oxygen. The overall process thus allowed the replacement of stoichiometric amounts of external oxidants with a suitable PC. Following this

NHC-catalyzed enantioselective synthesis of β-trifluoromethyl-β-hydroxyamides

• Alyn T. Davies,
• Mark D. Greenhalgh,
• Alexandra M. Z. Slawin and
• Andrew D. Smith

Beilstein J. Org. Chem. 2020, 16, 1572–1578, doi:10.3762/bjoc.16.129

• opening with allylamine. Purification gave 17 and 18, respectively, in a moderate yield as single diastereoisomers and with a good enantioselectivity. The mechanism of this NHC redox process is believed to proceed through the following mechanism (Scheme 3): After deprotonation of the triazolium salt

Five-component, one-pot synthesis of an electroactive rotaxane comprising a bisferrocene macrocycle

• Natalie Lagesse,
• Luca Pisciottani,
• Maxime Douarre,
• Pascale Godard,
• Brice Kauffmann,
• Vicente Martí-Centelles and
• Nathan D. McClenaghan

Beilstein J. Org. Chem. 2020, 16, 1564–1571, doi:10.3762/bjoc.16.128

• prove a valuable component for the construction of novel redox-active supramolecular systems, such as rotaxanes with strongly binding H-bonding templating sites, or indeed juxtaposed into existing functional architectures and benchmark variants. Results and Discussion Synthesis Our first approach to the

• . Rotaxane 1a presents a reversible redox transition at E1/2 = 0.51 V (that corresponds to E1/2 = +0.47 V vs SCE), where E1/2 = (Epa + Epc)/2 (Figure 6). As only one oxidation wave was observed, this showed that the two metal centres were electronically decoupled, while the oxidation potential of ferrocene

• was E1/2 = +0.380 V vs SCE showing that rotaxane 1a retained the redox properties of the parent ferrocene [21][22]. Importantly, the full reversibility of the one electron oxidation–reduction process attested to the stability of the electroactive system. Solid-state X-ray structure The solid-state

Heterogeneous photocatalysis in flow chemical reactors

• Christopher G. Thomson,
• Ai-Lan Lee and
• Filipe Vilela

Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125

• , wide electrochemical redox potentials, and photostability. However, these photocatalysts present serious drawbacks, such as toxicity, limited availability, and the overall cost of rare transition metal elements. This reduces their long-term viability, especially at an industrial scale. Heterogeneous

• , preventing recombination and expanding the redox potentials of the fused material [7]. The history and recent developments of these materials was reviewed by Anusuyadevi, Marre, Yu, and co-workers [7][196]. As briefly mentioned in Section 1.3, upconversion photocatalysis is a developing field of research

4-Hydroxy-3-methyl-2(1H)-quinolone, originally discovered from a Brassicaceae plant, produced by a soil bacterium of the genus Burkholderia sp.: determination of a preferred tautomer and antioxidant activity

• Dandan Li,
• Naoya Oku,
• Yukiko Shinozaki,
• Yoichi Kurokawa and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2020, 16, 1489–1494, doi:10.3762/bjoc.16.124

• immunity [33], among which redox enzymes and antioxidants are the direct countermeasures to neutralize the toxicity of ROS [34]. Limited examples of antioxidants include catecholamine melanin from a fungus Cryptococcus neoformans [35], 1,8-dihydroxynaphthalene melanin from fungi Wangiella dermatitidis and

Oxime radicals: generation, properties and application in organic synthesis

• Igor B. Krylov,
• Stanislav A. Paveliev,
• Alexander S. Budnikov and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2020, 16, 1234–1276, doi:10.3762/bjoc.16.107

• developed rapidly during the last years, and we believe that this review is essential for the demonstration of a new face of the chemistry of this class of N-oxyl radicals. There are reports on the iminoxyl radical involvement in redox processes occurring in living organisms, for example, in microsomal

Activated carbon as catalyst support: precursors, preparation, modification and characterization

• Melanie Iwanow,
• Tobias Gärtner,
• Volker Sieber and
• Burkhard König

Beilstein J. Org. Chem. 2020, 16, 1188–1202, doi:10.3762/bjoc.16.104

Photocatalysis with organic dyes: facile access to reactive intermediates for synthesis

• Stephanie G. E. Amos,
• Marion Garreau,
• Luca Buzzetti and
• Jerome Waser

Beilstein J. Org. Chem. 2020, 16, 1163–1187, doi:10.3762/bjoc.16.103

• electronically excited species. These reactive intermediates are then used to forge new chemical bonds or to induce structural modifications within the organic substrates. The versatility of these metal complexes is due to their wide operational redox windows, which allows them to interact via their excited

• transition metal-based photocatalysts [14][15][16][17][18]. In addition to their ready availability and low cost, these molecules are often biocompatible, and they can be easily functionalized in order to modulate their spectroscopical and redox features. In the last years, several classes of organic dyes

• each of these steps, the role of A or D is assumed by a redox-active agent, either the substrate, a sacrificial electron donor/acceptor, or a reactive intermediate. This approach, usually named photoredox catalysis, has known a remarkable growth in the last decade and has given access to both neutral

Synthesis and properties of quinazoline-based versatile exciplex-forming compounds

• Rasa Keruckiene,
• Simona Vekteryte,
• Ervinas Urbonas,
• Matas Guzauskas,
• Eigirdas Skuodis,
• Dmytro Volyniuk and
• Juozas V. Grazulevicius

Beilstein J. Org. Chem. 2020, 16, 1142–1153, doi:10.3762/bjoc.16.101

• . The potentials were calibrated against the standard ferrocene/ferrocenium (Fc/Fc+) redox system [24]. The ground-state geometries were optimized by using the B3LYP (Becke three parameters hybrid functional with Lee–Yang–Perdew correlation) [25] functional at the 6-31G (d, p) level of theory in vacuum

Synthesis of novel multifunctional carbazole-based molecules and their thermal, electrochemical and optical properties

• Nuray Altinolcek,
• Ahmet Battal,
• Mustafa Tavasli,
• William J. Peveler,
• Holly A. Yu and
• Peter J. Skabara

Beilstein J. Org. Chem. 2020, 16, 1066–1074, doi:10.3762/bjoc.16.93

• of compounds 7a and 7b are depicted in Figure 1. Thermal properties of compounds 7a and 7b are also summarised in Table 1. Electrochemical properties The redox behaviour of compounds 7a and 7b was investigated by cyclic voltammetry in dichloromethane solution under argon atmosphere using

• tetrabutylammonium hexafluorophosphate as the electrolyte (Figure 2). A platinum disk was used as a working electrode, silver wire as the reference electrode and platinum wire as the counter electrode. The ferrocene-ferrocenium redox couple was used as an internal reference. At positive potentials, compounds 7a and

Synthesis and properties of tetrathiafulvalenes bearing 6-aryl-1,4-dithiafulvenes

• Aya Yoshimura,
• Hitoshi Kimura,
• Kohei Kagawa,
• Mayuka Yoshioka,
• Toshiki Itou,
• Dhananjayan Vasu,
• Takashi Shirahata,
• Hideki Yorimitsu and
• Yohji Misaki

Beilstein J. Org. Chem. 2020, 16, 974–981, doi:10.3762/bjoc.16.86

• Abstract Novel multistage redox tetrathiafulvalenes (TTFs) bearing 6-aryl-1,4-dithiafulvene moieties were synthesized by palladium-catalyzed direct C–H arylation. In the presence of a catalytic amount of Pd(OAc)2, P(t-Bu3)·HBF4, and an excess of Cs2CO3, the C–H arylation of TTF with several aryl bromides

• of 1,3-dithiole rings to aromatic rings appears very appealing since these allow to produce novel multistage redox systems. However, such molecules could formerly not be synthesized by conventional approaches. In 2011, a breakthrough synthesis of arylated TTF derivatives by a palladium-catalyzed

• direct C–H arylation was reported, and the structural and electrochemical properties of the products were clarified [30]. This motivated us to synthesize novel multistage redox-TTFs bearing 1,3-dithiole rings on aromatic rings, 1–3 (Figure 1). In addition, we focused on cross-conjugated systems with 1,3

Recent applications of porphyrins as photocatalysts in organic synthesis: batch and continuous flow approaches

• Rodrigo Costa e Silva,
• Luely Oliveira da Silva,
• Aloisio de Andrade Bartolomeu,
• Timothy John Brocksom and
• Kleber Thiago de Oliveira

Beilstein J. Org. Chem. 2020, 16, 917–955, doi:10.3762/bjoc.16.83

• , planarity and special electronic characteristics to these compounds. As it is well-known, tetrapyrrolic compounds are considered to be the “pigments of life” since they play a key role in essential biological processes, such as photosynthesis (chlorophylls and bacteriochlorophylls), redox reactions for