N-Arylphenothiazines as strong donors for photoredox catalysis – pushing the frontiers of nucleophilic addition of alcohols to alkenes

• Fabienne Speck,
• David Rombach and
• Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2019, 15, 52–59, doi:10.3762/bjoc.15.5

• after 20 h of irradiation. Keywords: addition; phenothiazine; photochemistry; photoredox catalysis; redox potential; Introduction Visible-light photoredox catalysis has become a precious tool in modern synthetic organic chemistry and experiences a continuously growing interest in industrial

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

• the photocatalytical cycle, photoredox catalysts must be chosen with suitable redox potential to perform an oxidation or a reduction with other additives presented above. Thus, redox potentials of additives are resumed in Table 1. Indeed, additives and photoredox catalysts are involved into redox

• presented in Table 1 because the driving force of its reactivity is more its bond dissociation energy (BDE) than its redox potential. Indeed, this compound obeys to a pure hydrogen transfer mechanism. This corresponds to a hydrogen transfer from (TMS)3SiH to the triplet excited state of the PC. Thus, to

• equation and the redox potential in Table 8) for the electron-transfer reaction is possible both with electron acceptor such as iodonium salt and electron donor such as EDB [76]. In a three-component system A3/Iod/EDB (where Iod stands for bis(4-tert-butylphenyl)iodonium hexafluorophosphate), both

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

• substituents (to modulate the redox potential) on the electrocyclization was examined. In the series of derivatives with 6-membered rings, both the E- and the Z-isomer convert to the closed isomer, whereas for the 7-membered rings no cyclization from the E-isomer was observed. For both stiff and normal

Learning from B₁₂ enzymes: biomimetic and bioinspired catalysts for eco-friendly organic synthesis

• Keishiro Tahara,
• Ling Pan,
• Toshikazu Ono and
• Yoshio Hisaeda

Beilstein J. Org. Chem. 2018, 14, 2553–2567, doi:10.3762/bjoc.14.232

• shown in Figure 2a. The remarkable in vivo and in vitro characters of B12 are summarized as follows: B12 shows good accessibility to Co(I) species with a redox potential (the Co(II)/Co(I) couple in the base-off form) of −500 mV vs the standard hydrogen electrode [21], because of the monoanionic corrin

• -driven catalytic system for the dechlorination of DDT using 1 as catalyst and [Ru(bpy)3]Cl2 as photosensitizer [102]. The redox potential of [Ru(bpy)3]Cl2 for Ru(II)/Ru(I) couple is −1.35 V vs SCE in CH3CN. Thus, 1 was reduced to the Co(I) species by the photosensitizer in the presence of triethanolamine

Bioinspired cobalt cubanes with tunable redox potentials for photocatalytic water oxidation and CO₂ reduction

• Zhishan Luo,
• Yidong Hou,
• Jinshui Zhang,
• Sibo Wang and
• Xinchen Wang

Beilstein J. Org. Chem. 2018, 14, 2331–2339, doi:10.3762/bjoc.14.208

• cubane catalysts. However, most of the researches focused on the oxidative properties of the Co4O4 core [53], and its use for reduction reactions is rarely covered. Theoretically, the redox potential of Co4O4 cubane clusters should be tuned by virtue of different ligand substitutions, thus it is highly

• pyridine ligand provides further insight into the factors that affect the redox potential and tailor the catalytic performance. Furthermore, by exploring the structure–function relationship at the molecular level offers a useful guidance for the design and construction of high-performance earth-abundant

• allows us to scrutinize the interplay between electronic effects and redox potential caused by ligand modifications within the series of Co4O4 cubane clusters. The ligand modification strategy developed here provides a rational, precise and cost-effective way for the chemical design and synthesis of

Applications of organocatalysed visible-light photoredox reactions for medicinal chemistry

• Michael K. Bogdos,
• Emmanuel Pinard and
• John A. Murphy

Beilstein J. Org. Chem. 2018, 14, 2035–2064, doi:10.3762/bjoc.14.179

• half reaction (2) the redox potential is referred to by the notation Ered (Eosin Y/Eosin Y•−). The symbol “*” serves to denote when a species is in an excited electronic state, which then leads the general format adopted in this review to describe redox potentials of photocatalysts to become E*x (Ox

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

• (homogeneous). The benefit of the presence of a mediator is the switch of the sluggish heterogeneous electron transfer between electrode and substrate to a rapid homogeneous redox reaction between mediator and substrate. Further, the mediator’s redox potential must be below or above of that of the substrate

• tuning of the redox potential. A single class of ferrocene compounds with similar chemical and physical characteristics, yet covering a broad range of electrochemical potentials should circumvent this problem. To increase the ferrocene/ferrocenium potential, electron-withdrawing substituents are required

• stretching vibration delivers a useful in operando probe substantiating the stability of the redox mediator and enabling quantification of both redox partners and hence estimation of the actual concentration-dependent redox potential in solution. UV–vis spectroelectrochemistry of esters 1–4 Analogous to the

BODIPY-based fluorescent liposomes with sesquiterpene lactone trilobolide

• Ludmila Škorpilová,
• Silvie Rimpelová,
• Michal Jurášek,
• Miloš Buděšínský,
• Jana Lokajová,
• Roman Effenberg,
• Petr Slepička,
• Tomáš Ruml,
• Eva Kmoníčková,
• Pavel B. Drašar and
• Zdeněk Wimmer

Beilstein J. Org. Chem. 2017, 13, 1316–1324, doi:10.3762/bjoc.13.128

• [14][15][16], drugs [17], cell organelle markers, for antibody, peptide and nucleic acid labelling [18][19][20], for pH [21], metal [22][23] and redox potential sensing (well-reviewed in Boens et al. [24]), as well as for the development of photodynamically active agents [25][26]. In this work, we

3,6-Carbazole vs 2,7-carbazole: A comparative study of hole-transporting polymeric materials for inorganic–organic hybrid perovskite solar cells

• Wei Li,
• Munechika Otsuka,
• Takehito Kato,
• Yang Wang,
• Takehiko Mori and
• Tsuyoshi Michinobu

Beilstein J. Org. Chem. 2016, 12, 1401–1409, doi:10.3762/bjoc.12.134

• -EDOT were calculated according to Equation 1: where φFc/Fc+ is the redox potential of the ferrocene/ferrocenium (Fc/Fc+) couple measured under the same conditions (in this case, 0.09 V vs the Ag/Ag+electrode). 2,7-Cbz-EDOT has a deeper HOMO level than 3,6-Cbz-EDOT. This was also the case for the lowest

Synthesis and photophysical characteristics of polyfluorene polyrotaxanes

• Aurica Farcas,
• Giulia Tregnago,
• Ana-Maria Resmerita,
• Pierre-Henri Aubert and
• Franco Cacialli

Beilstein J. Org. Chem. 2015, 11, 2677–2688, doi:10.3762/bjoc.11.288

• gap (ΔEg) using ferrocene (Fc) as reference [51]. The IP, EA energy levels and ΔEg were calculated according to Equations 1–3 [52][53]. where: −4.80 eV represents the position of the Fc+/Fc redox couple in the energetic diagram [51]; +0.44 V is the redox potential of Fc+/Fc vs Ag. As indicated in

Preparative semiconductor photoredox catalysis: An emerging theme in organic synthesis

• David W. Manley and
• John C. Walton

Beilstein J. Org. Chem. 2015, 11, 1570–1582, doi:10.3762/bjoc.11.173

• where the electron can reduce an electron acceptor with a suitable redox potential to a radical anion (A–•) and/or the hole can oxidize an electron donor to the radical cation (D+•, Figure 1). Recombination, whereby the electron drops back down to the VB, occurs in competition with this in the bulk of

• employs an acceptor precursor with a suitable redox potential to pick up e– from the semiconductor with production of a radical anion capable of transforming to a neutral radical. In this case a sacrificial donor is needed to scavenge the holes (usually an alcohol or an amine). Occasionally, as in some of

New tris- and pentakis-fused donors containing extended tetrathiafulvalenes: New positive electrode materials for rechargeable batteries

• Shintaro Iwamoto,
• Yuu Inatomi,
• Daisuke Ogi,
• Satoshi Shibayama,
• Yukiko Murakami,
• Minami Kato,
• Kazuyuki Takahashi,
• Kazuyoshi Tanaka,
• Nobuhiko Hojo and
• Yohji Misaki

Beilstein J. Org. Chem. 2015, 11, 1136–1147, doi:10.3762/bjoc.11.128

• = −0.04 V) were more negative by 0.13 and 0.16 V than the first redox potential of a TTPY derivative 2e (E1 = +0.12 V) measured under the identical conditions. The first redox waves of 5d and 7d involved two-electron transfer processes, and that E1 of the extended donors 3c and 18 (−0.06 V) was lower than

Donor–acceptor type co-crystals of arylthio-substituted tetrathiafulvalenes and fullerenes

• Xiaofeng Lu,
• Jibin Sun,
• Shangxi Zhang,
• Longfei Ma,
• Lei Liu,
• Hui Qi,
• Yongliang Shao and
• Xiangfeng Shao

Beilstein J. Org. Chem. 2015, 11, 1043–1051, doi:10.3762/bjoc.11.117

• and Discussion Synthesis and compositions On the basis of hundreds of experimental runs, we found that the Ar-S-TTFs possessing the first redox potential (E1/21) smaller than 0.6 V could form the co-crystal-type complexes with fullerene molecules C60 and/or C70, whereas those with E1/21 > 0.6 V could

Glycoluril–tetrathiafulvalene molecular clips: on the influence of electronic and spatial properties for binding neutral accepting guests

• Yoann Cotelle,
• Marie Hardouin-Lerouge,
• Stéphanie Legoupy,
• Olivier Alévêque,
• Eric Levillain and
• Piétrick Hudhomme

Beilstein J. Org. Chem. 2015, 11, 1023–1036, doi:10.3762/bjoc.11.115

• yet reported. The redox potential (+ 0.87 V vs Fc+/Fc) of the NOSbF6 reagent is in agreement to allow the oxidation of TTF units. Chemical oxidation led to the rapid disappearance of the band at 320 nm attributed to the neutral TTF derivative and to the concomitant development of new bands

Bis(vinylenedithio)tetrathiafulvalene analogues of BEDT-TTF

• Erdal Ertas,
• İlknur Demirtas and
• Turan Ozturk

Beilstein J. Org. Chem. 2015, 11, 403–415, doi:10.3762/bjoc.11.46

• at 0 oC, add 20% HCl, then rt, overnight. Reaction and conditions (i) P4S10, NaHCO3, toluene, reflux, 3 h; (ii) P4S10, p-TSA, toluene, reflux, 3 h; (iii) (AcO)2Hg/AcOH, CHCl3, 3 h, rt; (iv) (EtO)3P, 110 °C, N2, 2 h. Ring closure methods and product yields. Redox potential of 29 and ET 3. in 1 mM MeCN

• solution, NaClO4 (0.1 M) vs Ag/AgCl, 100 mVs−1. Redox potential of 32a–d and 33a–c. and ET 3 in 1 mM CH2Cl2 solution, TBABF4 (0.1 M) vs Ag/AgCl, 115 mVs–1. Yields of the products 64, 65, 68–71. Redox potential of ET 3 and its analogues, ACN solution of 0.1 M NaClO4. Acknowledgements We thank Profesor John

An improved procedure for the preparation of Ru(bpz)₃(PF₆)₂ via a high-yielding synthesis of 2,2’-bipyrazine

• Danielle M. Schultz,
• James W. Sawicki and
• Tehshik P. Yoon

Beilstein J. Org. Chem. 2015, 11, 61–65, doi:10.3762/bjoc.11.9

• )32+) [10] has emerged as one of the most useful transition metal photocatalysts for oxidatively induced organic transformations (Figure 1). Due to the electron-deficient nature of its bipyrazyl ligands, the excited state redox potential of 2 is quite positive (+1.45 V vs SCE) [11]. Consequently, it

Redox active dendronized polystyrenes equipped with peripheral triarylamines

• Toshiki Nokami,
• Naoki Musya,
• Tatsuya Morofuji,
• Keiji Takeda,
• Masahiro Takumi,
• Akihiro Shimizu and
• Jun-ichi Yoshida

Beilstein J. Org. Chem. 2014, 10, 3097–3103, doi:10.3762/bjoc.10.326

• and Pd[P(t-Bu)3]2 as a catalyst [30] to obtain the dendrimer 5 having peripheral diarylamino groups in a yield of 77%. Compound 5 can serve as the precursor of dendritic diarylcarbenium ions having peripheral triarylamine structures. However, its redox potential (E1/2 = 0.79 V vs SCE) is much lower

Recent advances in the electrochemical construction of heterocycles

• Robert Francke

Beilstein J. Org. Chem. 2014, 10, 2858–2873, doi:10.3762/bjoc.10.303

• electrochemical reaction leads to an Umpolung of the functional group with the lower redox potential, triggering the ring-closure reaction between a nucleophilic and an electrophilic site. Another possibility for an intramolecular ring closure is represented by electrochemically induced radical cyclization

Solution processable diketopyrrolopyrrole (DPP) cored small molecules with BODIPY end groups as novel donors for organic solar cells

• Diego Cortizo-Lacalle,
• Calvyn T. Howells,
• Upendra K. Pandey,
• Joseph Cameron,
• Neil J. Findlay,
• Anto Regis Inigo,
• Tell Tuttle,
• Peter J. Skabara and
• Ifor D. W. Samuel

Beilstein J. Org. Chem. 2014, 10, 2683–2695, doi:10.3762/bjoc.10.283

• acetonitrile. In both cases, a Ag wire reference electrode and a Pt counter-electrode, in the presence of Bu4NPF6 (0.1 M), were used. All the values are quoted versus the redox potential of the ferrocene/ferrocenium couple. Normalised UV–vis absorption spectra of 9 (black), 10 (red) and DPP core (11, green) in

An integrated photocatalytic/enzymatic system for the reduction of CO₂ to methanol in bioglycerol–water

• Michele Aresta,
• Angela Dibenedetto,
• Tomasz Baran,
• Antonella Angelini,
• Przemysław Łabuz and
• Wojciech Macyk

Beilstein J. Org. Chem. 2014, 10, 2556–2565, doi:10.3762/bjoc.10.267

• thermodynamically and kinetically possible. This enables identification of the intermediates in the reaction pathway of the photocatalytic cycle based on [CrF5(H2O)]2−@TiO2 as an exciton generator and confirmation that the rhodium complex is an e−-transfer agent. The redox potential of the [Cp*Rh(bpy)H2O]2+/[Cp*Rh

• (bpy)H]+ couple was determined by Steckhan et al. and was shown to be equal to −0.32 V vs NHE. The redox potential of the conduction band of [CrF5(H2O)]2−@TiO2 is −0.58 V vs NHE, as measured in the present study using a previously published methodology [24]. The electrode covered by [CrF5(H2O)]2−@TiO2

On the mechanism of photocatalytic reactions with eosin Y

• Michal Majek,
• Fabiana Filace and
• Axel Jacobi von Wangelin

Beilstein J. Org. Chem. 2014, 10, 981–989, doi:10.3762/bjoc.10.97

• -carbonyl, and aryl moieties [9][10]. Among them, eosin Y, the 2’,4’,5’,7’-tetrabromo derivative of fluorescein, has been most widely employed. The redox potential of the EY+/EY* pair of 1.1 V (vs. SCE) is experimentally not available as both of the compounds are short-lived intermediates. However, the

• redox potential can be obtained indirectly via analysis of the thermodynamic cycle involving the energy of the triplet state eosin Y* (T1) (derived from fluorescence measurements) and the energy of the radical cation eosin Y+• (derived from cyclovoltammetric experiments, for more details see Supporting

• thermodynamic feasibility of a redox process is determined by the difference of redox potentials of the two half reactions. The redox potential of most arenediazonium salts (redox pair I/II, Scheme 2) is close to 0 V vs. SCE [23][24]. The redox potentials of the short-lived adducts III/IV are unknown and

Direct and indirect single electron transfer (SET)-photochemical approaches for the preparation of novel phthalimide and naphthalimide-based lariat-type crown ethers

• Dae Won Cho,
• Patrick S. Mariano and
• Ung Chan Yoon

Beilstein J. Org. Chem. 2014, 10, 514–527, doi:10.3762/bjoc.10.47

• being controlled by the redox potential of each donor site. Moreover, in these cases, the product yields will rely on the relative rates of the competing fragmentation reactions (kE1 vs kE2) as a result of the fact that the energy barriers for these processes are higher than that of intrasite-SET [31

Halogenated volatiles from the fungus Geniculosporium and the actinomycete Streptomyces chartreusis

• Tao Wang,
• Patrick Rabe,
• Christian A. Citron and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2013, 9, 2767–2777, doi:10.3762/bjoc.9.311

• for Y. Approximate number of known halogenated natural products and redox potential and natural abundance of the halogenides in sea water. NMR spectroscopic data and GC retention indices of all constitutional isomers of chlorodimethoxybenzene in comparison to natural X. NMR spectroscopic data and GC

Advancements in the mechanistic understanding of the copper-catalyzed azide–alkyne cycloaddition

• Regina Berg and
• Bernd F. Straub

Beilstein J. Org. Chem. 2013, 9, 2715–2750, doi:10.3762/bjoc.9.308

• (1 mol %) and TBTA (1 mol %) under aerobic conditions [64]. Cyclic voltammetry measurements have supported the hypothesis of TBTA influencing the redox activity of copper(I), as the redox potential of the Cu(I)/Cu(II) pair was shown to rise by approximately 300 mV when the water-soluble derivative

Stability of SG1 nitroxide towards unprotected sugar and lithium salts: a preamble to cellulose modification by nitroxide-mediated graft polymerization

• Guillaume Moreira,
• Laurence Charles,
• Mohamed Major,
• Florence Vacandio,
• Yohann Guillaneuf,
• Catherine Lefay and
• Didier Gigmes

Beilstein J. Org. Chem. 2013, 9, 1589–1600, doi:10.3762/bjoc.9.181

• and are listed in Table 1. The cyclic voltammograms of SG1 and LiCl in DMF and MeOH are presented in Figure 10. The redox potential of the reduction of Li+/Li in DMF is around −2.1 V as already reported [31]. Initially only the SG1 nitroxide, Li+ and Cl− were present in the media. The only possible

• of the solvent (DMF or DMA) with the lithium salt (LiCl or LiBr). The first hypothesis to explain the SG1 consumption in DMA/LiCl was based on the SG1 oxidation by Cl2 (or Br2 in the case of LiBr lithium salt). However, the study by cyclic voltammetry of the redox potential of SG1 and LiCl could not

• reactive, but all regioisomers are possible. (Reversible) redox system of nitroxide. Hydrolysis of DMA in the presence of LiCl. Disproportionation of nitroxide 1 by acid treatment. Experimental redox potential of the oxidation (Eox) and of the reduction (Ered) in DMF and MeOH.a Acknowledgements The