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

• . 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

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

• venerable transformations [39][40], allowing the smooth generation of alkyl radicals from carboxylic acid derivatives. One of the main strategies for accessing C(sp3) radicals from carboxylic acids relies on the oxidation of the CO2H group. However, the high oxidation potential of these species makes them

• hydrogen atom source (PhSH). The reaction allows the direct conversion of carboxylic acids, e.g., 3.1 to the corresponding alkanes, e.g., 3.2. The scope includes carboxylic acids that were previously recalcitrant to other oxidative photocatalytic decarboxylations due to their high oxidation potential

Accelerating fragment-based library generation by coupling high-performance photoreactors with benchtop analysis

• Quentin Lefebvre,
• Christophe Salomé and
• Thomas C. Fessard

Beilstein J. Org. Chem. 2020, 16, 982–988, doi:10.3762/bjoc.16.87

• to nickel(0) is believed to occur by β-hydride elimination on a sacrificial amount of amine [10]. The strained character of azaspiro[3,3]heptane might prevent this event. On the other hand, pyramidalization at nitrogen is much more important in azetidines [16][17][18]. This might lower the oxidation

• potential of the arylated product and promote oxidative decomposition. Several spirocyclic compounds with larger ring sizes could be coupled to 3-bromopyridine to give products 4c, 4d, 5a and 5b, provided that steric hindrance was not too high (see 5c). Surprisingly, oxetanes appear to be incompatible with

Copper catalysis with redox-active ligands

• Agnideep Das,
• Yufeng Ren,
• Cheriehan Hessin and
• Marine Desage-El Murr

Beilstein J. Org. Chem. 2020, 16, 858–870, doi:10.3762/bjoc.16.77

• interaction greatly affected the chemical properties. They also reported that complexes that had higher oxidation potential and went through irreversible oxidation were not good catalysts for the oxidation of benzyl alcohol to benzaldehyde (0–30% yields, e.g., PhPhCuO.S.2, O.S.x signifies oxidation state and

• incorporating two copper(I) centers. These specific quinidine ligands have the ability to supply electrons to the metal center thanks to their low oxidation potential and can shuttle up to two electrons to the copper centers. The specific geometry of this ligand also has an influence on the rate of electron

Photophysics and photochemistry of NIR absorbers derived from cyanines: key to new technologies based on chemistry 4.0

• Bernd Strehmel,
• Christian Schmitz,
• Ceren Kütahya,
• Yulian Pang,
• Anke Drewitz and
• Heinz Mustroph

Beilstein J. Org. Chem. 2020, 16, 415–444, doi:10.3762/bjoc.16.40

Visible-light-induced addition of carboxymethanide to styrene from monochloroacetic acid

• Kaj M. van Vliet,
• Nicole S. van Leeuwen,
• Albert M. Brouwer and
• Bas de Bruin

Beilstein J. Org. Chem. 2020, 16, 398–408, doi:10.3762/bjoc.16.38

• voltammetry to determine the oxidation potential (EOx) of monochloroacetic acid in acetonitrile (Figure 2). This way it could be verified, if monochloroacetic acid can quench the excited state of one of the common photoredox catalysts. In Figure 1 the cyclic voltammogram of monochloroacetic acid is shown. One

Synthesis of a dihalogenated pyridinyl silicon rhodamine for mitochondrial imaging by a halogen dance rearrangement

• Jessica Matthias,
• Thines Kanagasundaram,
• Klaus Kopka and
• Carsten S. Kramer

Beilstein J. Org. Chem. 2019, 15, 2333–2343, doi:10.3762/bjoc.15.226

• moiety of silicon rhodamines could tune the HOMO energy level [15]. Depending on the oxidation potential and the HOMO energy level of the benzene moiety, the quantum yield was greatly altered but absorption and emission bands remained unchanged. Thus, the quantum yield shows a direct connection to the

• negative value of the HOMO energy level and/or the oxidation potential [15], but it is also influenced by other factors. Nonradiative quenching (e.g., bond rotation) can effectively contribute to depopulation of the fluorophore’s excited state [28], yielding a lower quantum yield. However, the rational

Small anion-assisted electrochemical potential splitting in a new series of bistriarylamine derivatives: organic mixed valency across a urea bridge and zwitterionization

• Keishiro Tahara,
• Tetsufumi Nakakita,
• Alyona A. Starikova,
• Takashi Ikeda,
• Masaaki Abe and
• Jun-ichi Kikuchi

Beilstein J. Org. Chem. 2019, 15, 2277–2286, doi:10.3762/bjoc.15.220

• substituents R at the para-position of the benzene adjacent to the nitrogen centers were synthesized to tune the oxidation potential of the nitrogen centers (Figure 1). According to a previously reported method for the synthesis of ureas [45], symmetric ureas 1 were synthesized from the corresponding amines

• with that for 1b. This substituent effect on the oxidation potential is typical for the reported NAr3 system [53]. Because the electron-donating group of the NAr3 unit destabilizes the MV state, the potential splitting for 1a is 50 mV smaller than that for 1b (Figure 2, top). Similar substituent

Synthesis of acremines A, B and F and studies on the bisacremines

• Nils Winter and
• Dirk Trauner

Beilstein J. Org. Chem. 2019, 15, 2271–2276, doi:10.3762/bjoc.15.219

• undergo Diels–Alder reactions with electron-rich dienophiles [13][14][15][16][17], treatment of 5 with Fukuzumi’s catalyst [18] under illumination with blue light only led to decomposition of the starting material (Table 1, entry 15). Notably, a photoredox catalyst with a lower oxidation potential could

Naphthalene diimides with improved solubility for visible light photoredox catalysis

• Barbara Reiß and
• Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2019, 15, 2043–2051, doi:10.3762/bjoc.15.201

• oxidation potential of 0.38 V vs SCE [59]. Together with the reduction potential of Ered = 0.69 V and E00 = 3.25 eV for NDI 1 (vide infra), this electron transfer is clearly exergonic (ΔG = Eox − Ered − E00 = −2.2 eV). NDI 6 shows a strong and broad fluorescence in CH2Cl2 with a maximum at 640 nm and a

Selenophene-containing heterotriacenes by a C–Se coupling/cyclization reaction

• Pierre-Olivier Schwartz,
• Sebastian Förtsch,
• Astrid Vogt,
• Elena Mena-Osteritz and
• Peter Bäuerle

Beilstein J. Org. Chem. 2019, 15, 1379–1393, doi:10.3762/bjoc.15.138

• ., a lowering of the oxidation potential with increasing number of selenium atoms (vide supra), seems to be blurred for the polymers. Published data for P(DTT) P1 is very similar showing an onset potential of −0.12 V vs Fc/Fc+ (calculated from 0.37 V vs Ag/AgCl) [46][52]. The redox characteristic of P1

Organometallic vs organic photoredox catalysts for photocuring reactions in the visible region

• Aude-Héloise Bonardi,
• Frédéric Dumur,
• Guillaume Noirbent,
• Jacques Lalevée and
• Didier Gigmes

Beilstein J. Org. Chem. 2018, 14, 3025–3046, doi:10.3762/bjoc.14.282

• electronically excited state which significantly changes the distribution of electrons in the molecule. Thus, chemical properties such as reactivity, oxidation potential or reduction potential change drastically. With appropriate donors or acceptors, electron charge transfer is possible via this excited state

• equation: where Eox is the oxidation potential of the electron donor, Ered the reduction potential of the electron acceptor, E* the excited state energy level and C the coulombic term for the initially formed ion pair (if there are ions in solution). For polar solvent, C is neglected. (TMS)3SiH is not

• photopolymerization initiation as shown in [53] (see Part 3). For this purpose, the Ir complex was more interesting than the Ru one because of the longer excited state lifetime, lower oxidation potential leading to higher interaction rate constants with additives used for ring-opening photopolymerization (e.g

Oxidative and reductive cyclization in stiff dithienylethenes

• Michael Kleinwächter,
• Ellen Teichmann,
• Lutz Grubert,
• Martin Herder and
• Stefan Hecht

Beilstein J. Org. Chem. 2018, 14, 2812–2821, doi:10.3762/bjoc.14.259

• Table S1 (Supporting Information File 1). For most ring-open compounds investigated, the E-isomer displayed a higher or at least equal oxidation potential when compared to the Z-isomer. This difference for both open isomers is rather surprising in view of their very similar absorption maxima in first

• line with the largely reduced HOMO–LUMO gap of the colored closed isomers implying an energetically higher and thus more accessible HOMO level. The first and second oxidation potential are shifted depending on the electron-donating or electron-withdrawing character of the attached substituents

• oxidation potential, hollow circles to the second oxidation potential (if available). For detailed data, see Table S1, for all respective cyclovoltammograms, see Figure S10 to Figure S27 in Supporting Information File 1. Cyclic voltammograms of sDTE66-PhCN. The reduction of a) E-sDTE66-PhCN (black line) is

Synthesis of aryl sulfides via radical–radical cross coupling of electron-rich arenes using visible light photoredox catalysis

• Amrita Das,
• Mitasree Maity,
• Simon Malcherek,
• Burkhard König and
• Julia Rehbein

Beilstein J. Org. Chem. 2018, 14, 2520–2528, doi:10.3762/bjoc.14.228

• (dtbpy)]PF6 as the photocatalyst. The reaction was carried out under nitrogen under visible-light irradiation at 455 nm. The oxidation potential of this test arene is 1.02 V vs SCE, which allows oxidation by [Ir(dF(CF3)ppy)2(dtbpy)]PF6 having an estimated excited state oxidation potential of 1.21 V vs

• addition of 1,2,4-trimethoxybenzene (oxidation potential 1.02 V vs SCE, Figure 3a). The values are similar to the estimated excited state oxidation potential of [Ir(dF(CF3)ppy)2(dtbpy)]PF6 ( +1.21 V vs SCE in acetonitrile). On the other hand, the luminescence was quenched negligible on addition of diphenyl

• )]PF6 and also did not give a sulfenylated product under our photocatalytic conditions. This is rationalized by the oxidation potential of anisole of 1.76 V vs SCE, which is higher than the estimated excited state oxidation potential of the photocatalyst. To elucidate, if the 1,3,5-TMB radical cation

Tetrathiafulvalene – a redox-switchable building block to control motion in mechanically interlocked molecules

• Hendrik V. Schröder and
• Christoph A. Schalley

Beilstein J. Org. Chem. 2018, 14, 2163–2185, doi:10.3762/bjoc.14.190

• so-called mixed-valence dimer (12) ●+. A mixed-valence dimer can be identified by splitting of the first TTF oxidation potential into two distinguishable waves. This change in redox behavior can be followed by electrochemical methods such as cyclic voltammetry. Another indication for a mixed-valence

• latter technique revealed an increase of oxidation potential for the first one-electron oxidation, but a second oxidation potential similar to that of the free axle. This indicates that the wheel already moves away from the TTF station upon the first oxidation to the TTF●+ radical cation. Another example

Rational design of boron-dipyrromethene (BODIPY) reporter dyes for cucurbit[7]uril

• Mohammad A. Alnajjar,
• Jürgen Bartelmeß,
• Robert Hein,
• Pichandi Ashokkumar,
• Mohamed Nilam,
• Werner M. Nau,
• Knut Rurack and
• Andreas Hennig

Beilstein J. Org. Chem. 2018, 14, 1961–1971, doi:10.3762/bjoc.14.171

• the 2,8-diethyl-1,3,7,9-tetramethyl-BODIPY core acceptor of 3 in acetonitrile [47], an oxidation potential of +0.0625 V for the aniline donor [48][49], and the vibrational zero electronic energy was determined as 2.46 eV from absorption and emission spectra. This gave ∆G values of −87.6 kJ mol−1 for 1

Recent advances in hypervalent iodine(III)-catalyzed functionalization of alkenes

• Xiang Li,
• Pinhong Chen and
• Guosheng Liu

Beilstein J. Org. Chem. 2018, 14, 1813–1825, doi:10.3762/bjoc.14.154

• first hypervalent iodine(III)-catalyzed reaction, in which the iodine(III) reagent was in situ generated by anodic oxidation under electrochemical conditions [36]. Critical to success of this process is that the oxidation potential of the catalysts should be much lower than those of the substrates and

Polysubstituted ferrocenes as tunable redox mediators

• Sven D. Waniek,
• Jan Klett,
• Christoph Förster and
• Katja Heinze

Beilstein J. Org. Chem. 2018, 14, 1004–1015, doi:10.3762/bjoc.14.86

• essentially reversible behaviour for the ferrocene/ferrocenium oxidation process (Figure 1, Figure S1, Supporting Information File 1). The electrochemical potentials cover a wide range, E1/2 = 260–900 mV vs FcH/FcH+ (Figure 1, Table 1). The oxidation potential of the tetraester 4 is very high with E1/2 = 900

Anodic oxidation of bisamides from diaminoalkanes by constant current electrolysis

• Tatiana Golub and
• James Y. Becker

Beilstein J. Org. Chem. 2018, 14, 861–868, doi:10.3762/bjoc.14.72

• studied by cyclic voltammetry and all of their redox potentials were found to be irreversible in acetonitrile. Their first oxidation potentials (in the range of 2.1–2.35 V vs Ag/AgCl) are summarized in Table 1. The first and second columns indicate that the longer the spacer the higher the oxidation

• potential. Also it is not surprising that the derivative with EWG (IV) is more difficult to oxidize than that with EDG (III). All bisamides derivatives exhibit one irreversible cathodic wave (not shown, at −2.2 to −2.4 V). Constant current electrolysis (CCE) at a current density of 20 mA/cm2 was carried out

The selective electrochemical fluorination of S-alkyl benzothioate and its derivatives

• Shunsuke Kuribayashi,
• Tomoyuki Kurioka,
• Shinsuke Inagi,
• Ho-Jung Lu,
• Biing-Jiun Uang and
• Toshio Fuchigami

Beilstein J. Org. Chem. 2018, 14, 389–396, doi:10.3762/bjoc.14.27

• these compounds have rather high oxidation potentials. DFT calculation of 1a indicated that the highest occupied molecular orbital (HOMO) is located at the sulfur atom (Figure 2). Although sulfur atoms are easily oxidized, the oxidation potential of 1a was found to be extremely high, that is due to the

• . Regardless of the electrolytic conditions, the anodic fluorination proceeded to provide the desired fluorinated product 2a except for the electrolysis performed in dimethoxyethane (DME) as the solvent (Table 1, entry 3). The oxidation potential of 1a is rather high, while that of DME is relatively low [24

Synthesis of fluoro-functionalized diaryl-λ³-iodonium salts and their cytotoxicity against human lymphoma U937 cells

• Prajwalita Das,
• Etsuko Tokunaga,
• Hidehiko Akiyama,
• Hiroki Doi,
• Norimichi Saito and
• Norio Shibata

Beilstein J. Org. Chem. 2018, 14, 364–372, doi:10.3762/bjoc.14.24

• biological evaluation, this is the first report to highlight the cytotoxicity of diaryliodonium salts against U937 cells. Since diaryliodonium salts are fundamentally oxidizing agents, there might be a stronger correlation between cytotoxicity and the oxidation potential of these salts. We will continue the

Recent advances on organic blue thermally activated delayed fluorescence (TADF) emitters for organic light-emitting diodes (OLEDs)

• Thanh-Tuân Bui,
• Fabrice Goubard,
• Malika Ibrahim-Ouali,
• Didier Gigmes and
• Frédéric Dumur

Beilstein J. Org. Chem. 2018, 14, 282–308, doi:10.3762/bjoc.14.18

• dihedral angle of T21–T23 contributed to spatially separate the HOMO from the LUMO orbitals. By electrochemistry, an appreciable reduction of the oxidation potential was detected (+0.87 V) for T21 which is substituted at the 1,8-positions of the donor whereas T20, T22 and T23 exhibited the same oxidation

• - and T23-based devices, respectively. As anticipated, a lower color purity was obtained for T21-based devices resulting from its lower oxidation potential. Recently, a significant enhancement of blue OLED performances was obtained by replacing the triazine acceptor by a 2,4,6-triphenylpyrimidine unit

Vinylphosphonium and 2-aminovinylphosphonium salts – preparation and applications in organic synthesis

• Anna Kuźnik,
• Roman Mazurkiewicz and
• Beata Fryczkowska

Beilstein J. Org. Chem. 2017, 13, 2710–2738, doi:10.3762/bjoc.13.269

• under a nitrogen atmosphere in dichloromethane solution on a graphite anode and a cathode of stainless steel at a constant current of 20 mA (Scheme 12). Depending on the cycloalkene used, the target vinylphosphonium salt was obtained in a yield of 53–66% [19]. Since the oxidation potential of

Synthesis and application of trifluoroethoxy-substituted phthalocyanines and subphthalocyanines

• Satoru Mori and
• Norio Shibata

Beilstein J. Org. Chem. 2017, 13, 2273–2296, doi:10.3762/bjoc.13.224

• electronegativity of fluorine and has been successfully isolated. In measurements of cyclic voltammetry, iron phthalocyanines with an alkoxy group show a lower first oxidation potential than unsubstituted iron phthalocyanine, but TFEO-FePc shows a more difficult oxidation process than unsubstituted iron

Diastereoselective anodic hetero- and homo-coupling of menthol-, 8-methylmenthol- and 8-phenylmenthol-2-alkylmalonates

• Matthias C. Letzel,
• Hans J. Schäfer and
• Roland Fröhlich

Beilstein J. Org. Chem. 2017, 13, 33–42, doi:10.3762/bjoc.13.5

• literature [25], where the oxidation potential for anisole and toluene was determined to be 1.15 V and 1.35 V (vs Ag/Ag+), respectively. In the Kolbe electrolysis a critical potential of 1.9 to 2.2 V (vs Ag/AgCl) has to be exceeded. At this potential the coverage of the electrode with carboxylate ions

• increases sharply, the oxygen evolution is inhibited, solvent oxidation is retarded and the Kolbe electrolysis is promoted [26]. If in the carboxylate an additional electrophore with a lower oxidation potential than the critical potential is present it is oxidized instead of the carboxylate group. This is