Trifluoromethyl-substituted tetrathiafulvalenes

• Olivier Jeannin,
• Frédéric Barrière and
• Marc Fourmigué

Beilstein J. Org. Chem. 2015, 11, 647–658, doi:10.3762/bjoc.11.73

• EDT-TTF-CF3 dimers and TCNQ in the solid state. A radical cation salt of EDT-TTF-CF3 is also obtained upon electrocrystallisation in the presence of the FeCl4− anion. In this salt, formulated as (EDT-TTF-CF3)(FeCl4), the (EDT-TTF-CF3)+• radical cations are associated two-by-two into centrosymmetric

• dyads with a strong pairing of the radical species in a singlet state. Keywords: electrochemistry; electron withdrawing group (EWG); fluorine; tetrathiafulvalene (TTF); Introduction Following three decades of extensive work toward the elaboration of conducting radical cation salts from

• tetrathiafulvalene (TTF) derivatives with electron-rich alkyl (tetramethyltetrathiafulvalene: TMTTF, tetramethyltetraselenafulvalene: TMTSF) or thioalkyl (ethylenedithiotetrathiafulvalene: EDT-TTF, bis(ethylenedithio)tetrathiafulvalene: BEDT-TTF) substituents [1], investigations of radical cation salts of

Photocatalytic nucleophilic addition of alcohols to styrenes in Markovnikov and anti-Markovnikov orientation

• Martin Weiser,
• Sergej Hermann,
• Alexander Penner and
• Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2015, 11, 568–575, doi:10.3762/bjoc.11.62

• inefficient back electron transfer indicated that loss of polar attraction after rapid protonation of the substrate radical anion might lead to diffusion and separation of the photocatalyst from the intermediate product-forming radical cation. If it was assumed that back electron transfer was a strongly

Metal-free one-pot synthesis of 2-substituted and 2,3-disubstituted morpholines from aziridines

• Hongnan Sun,
• Binbin Huang,
• Run Lin,
• Chao Yang and
• Wujiong Xia

Beilstein J. Org. Chem. 2015, 11, 524–529, doi:10.3762/bjoc.11.59

• mechanism was proposed as shown in Scheme 4. Initially, aziridine 1a might participate in single-electron transfer (SET) with the persulfate anion to render the radical cation A [32][34]. Concerted ring opening and nucleophilic addition leads to amino radical intermediate B, which is converted to the

• -substituted and 2,3-disubstituted morpholines. Compared with the previous procedure, this reaction is conducted with a simple and inexpensive ammonium persulfate salt as the oxidant to realize the ring opening of aziridines for the reaction with haloalcohols through a radical cation intermediate pathway

Eosin Y-catalyzed visible-light-mediated aerobic oxidative cyclization of N,N-dimethylanilines with maleimides

• Zhongwei Liang,
• Song Xu,
• Wenyan Tian and
• Ronghua Zhang

Beilstein J. Org. Chem. 2015, 11, 425–430, doi:10.3762/bjoc.11.48

• undergo an oxidative or reductive quenching cycle [48][49][50]. In this mechanism, a single electron transfer (SET) from 1 to 3EY* generates the amine radical cation 4, and at the same time, 3EY* is reduced to the EY•−. In the presence of oxygen, the photoredox catalytic cycle of EY is finished via a SET

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

• studied and has had the largest number of radical cation salts of its CT materials investigated at very low temperature [12][21][22][23][24]. In order to improve the properties of TTF type materials, various methods have been applied, including extension of π-conjugation through double bonds [25][26][27

• molecule [28][40]. The most notable superconductivity was observed with the radical cation salts derived from the electron-donor molecule bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) as a (BEDT-TTF)2Cu[N(CN)2]Br salt at 12.5 K (resistive onset) [24]. The tetrathiafulvalene (TTF) ring system is one of

Electrochemical oxidation of cholesterol

• Jacek W. Morzycki and
• Andrzej Sobkowiak

Beilstein J. Org. Chem. 2015, 11, 392–402, doi:10.3762/bjoc.11.45

• cleavage of the C3–O bond in the resulting radical cation leads to the formation of a hydroxyl radical and the steroidal carbocation. Such a mesomerically stabilized homoallylic carbocation can react with any nucleophile present in the reaction mixture. In the absence of better nucleophiles it reacts with

Functionalized branched EDOT-terthiophene copolymer films by electropolymerization and post-polymerization “click”-reactions

• Miriam Goll,
• Adrian Ruff,
• Erna Muks,
• Felix Goerigk,
• Beatrice Omiecienski,
• Ines Ruff,
• Rafael C. González-Cano,
• Juan T. Lopez Navarrete,
• M. Carmen Ruiz Delgado and
• Sabine Ludwigs

Beilstein J. Org. Chem. 2015, 11, 335–347, doi:10.3762/bjoc.11.39

• charged PEDOT species with an absorption of the radical cation around 890 nm. This is in accordance to literature where the PEDOT radical cation is described with an absorption maximum around 880 nm [24]. Only when approaching the second oxidation wave around +0.9 V the absorption band at 450 nm is

• decreasing, revealing a new absorption at 780 nm which can be attributed to the radical cation formation of P3T matching the literature value [24]. To our knowledge this is one of very few examples [48][49], where a polymer blend provides the separated absorption and redox properties of the homopolymers

• decreasing uniformly and steadily while at 830 nm a single band is ascending, which indicates the formation of the charged radical cation species. This is in agreement with our earlier data where we showed this uniform steady decrease of the band at 830 nm absorption during the oxidation for P(EDOT-co-3T

Photovoltaic-driven organic electrosynthesis and efforts toward more sustainable oxidation reactions

• Bichlien H. Nguyen,
• Robert J. Perkins,
• Jake A. Smith and
• Kevin D. Moeller

Beilstein J. Org. Chem. 2015, 11, 280–287, doi:10.3762/bjoc.11.32

• ][25]. The reaction requires a careful balance between the initial condensation reaction and the oxidative step with either CAN or DDQ serving as the mediator. In the third reaction (Scheme 7), an intramolecular alcohol nucleophile was added to an olefin coupling reaction [26]. When a radical cation

• barriers of quaternary carbon and six-membered ring formation. The use of the second nucleophile and a fast initial trapping reaction reduced the cation character of the radical cation intermediate, slowed competitive elimination reactions, and allowed for the desired quaternary carbon formation. In these

Anionic sigmatropic-electrocyclic-Chugaev cascades: accessing 12-aryl-5-(methylthiocarbonylthio)tetracenes and a related anthra[2,3-b]thiophene

• Laurence Burroughs,
• John Ritchie,
• Mkhethwa Ngwenya,
• Dilfaraz Khan,
• William Lewis and
• Simon Woodward

Beilstein J. Org. Chem. 2015, 11, 273–279, doi:10.3762/bjoc.11.31

• (ca. 800 nm) of 7a and 7j showed dielectric behaviour (σ <10−10 S cm−1) indicating that additional derivitisation and radical cation salt formation is required for the attainment of high electrical conductivity, as in the case of tetrathiotetracene [30]. Conclusion Typical [3,3]-sigmatropic

3α,5α-Cyclocholestan-6β-yl ethers as donors of the cholesterol moiety for the electrochemical synthesis of cholesterol glycoconjugates

• Aneta M. Tomkiel,
• Adam Biedrzycki,
• Jolanta Płoszyńska,
• Dorota Naróg,
• Andrzej Sobkowiak and
• Jacek W. Morzycki

Beilstein J. Org. Chem. 2015, 11, 162–168, doi:10.3762/bjoc.11.16

• an intermediate radical cation occurs, thus leading to a mesomerically stabilized homoallylic carbocation and a hydroxyl radical (Scheme 1) [2]. However, the glycosylation reaction was not very efficient due to competition between the sugar alcohol and cholesterol for the carbocation [3]. If

• during electrochemical oxidation by cleavage of the carbon–oxygen bond in an intermediate radical-cation. For this reason, i-cholesteryl ethers seemed to be suitable donors of the cholesterol moiety for the electrochemical synthesis of cholesterol glycoconjugates. A series of i-cholesterol derivatives 6b

• -hydroxyphenyl i-cholesteryl ether (6g) can be attributed to the electrochemical oxidation of the phenol type substituent, which is responsible for an additional peak at low potentials. The process is usually irreversible, resulting from the fast deprotonation of the primarily generated radical cation [7]. The

Highly selective electrochemical fluorination of dithioacetal derivatives bearing electron-withdrawing substituents at the position α to the sulfur atom using poly(HF) salts

• Bin Yin,
• Shinsuke Inagi and
• Toshio Fuchigami

Beilstein J. Org. Chem. 2015, 11, 85–91, doi:10.3762/bjoc.11.12

• fluorination of dithioacetals 1b, 1d, and 1f is shown in Scheme 3. The fluorination reaction is initiated by electron transfer from a sulfur atom of the substrate to generate the corresponding radical cation B, which traps a fluoride ion to afford radical C. This is followed by a further oxidation to give

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

• is an effective photocatalyst in oxidatively induced photoredox transformations where less strongly oxidizing complexes (e.g., 1) are not successful. For instance, we have reported that 2 is uniquely capable of promoting radical cation mediated Diels–Alder cycloadditions [12], radical thiol–ene

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

• 9 seem to be ascribable to the interaction of the initially formed radical cation from the triarylamine moiety with a neighboring neutral triarylamine moiety, which disfavors the second electron transfer from the latter, although the details of this reaction are not clear as yet [49][50]. This is

Recent advances in the electrochemical construction of heterocycles

• Robert Francke

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

• anodic oxidation of electron-rich olefins such as enol ethers 1 in methanolic solution generates radical cation 2 which can be used for a number of cyclization reactions (Scheme 2) [32][33]. Moeller et al. demonstrated that by intramolecular trapping of this highly reactive intermediate with a tethered

• order to obtain reasonable reaction rates. When the radical cation is trapped with a hydroxy group, the use of 2,6-lutidine is sufficient. However, a stronger base such as NaOMe is needed when tosylamines are converted in order to facilitate the cyclization reaction and to suppress intermolecular

• serves as supporting electrolyte and as fluoride source for mediation of the reaction. In absence of fluoride, the formation of the cyclization product was not observed. The authors proposed a mechanism, in which after initial one-electron oxidation the resulting radical cation 48 is attacked by a

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

• +0.73 V. In both cases, the first oxidation wave is assigned to the formation of the radical cation on one of the bi/terthiophene segments of the molecule. The lower oxidation potential for 10 compared to 9 is consistent with the tendency to decrease the oxidation potential when the oligothiophene chain

• slightly less negative with increased conjugation, whilst the DPP core becomes less positive with increased conjugation in the radical cation form. The increase in conjugation allows charge to be more evenly distributed across the whole molecule. However, the inclusion of BODIPY accepting units presents a

• compounds 9 and 10: radical anion (blue), neutral (black) and radical cation (red) geometries. Electrostatic potential charges for each unit in (2Th)2DPP and (3Th)2DPP radical anion (blue), neutral (black) and radical cation (red) geometries, as analogues of compounds 9 and 10. Frontier orbitals for radical

Oxidative phenylamination of 5-substituted 1-hydroxynaphthalenes to N-phenyl-1,4-naphthoquinone monoimines by air and light “on water”

• Julio Benites,
• Juan Meléndez,
• Cynthia Estela,
• David Ríos,
• Luis Espinoza,
• Iván Brito and
• Jaime A. Valderrama

Beilstein J. Org. Chem. 2014, 10, 2448–2452, doi:10.3762/bjoc.10.255

• (1) with phenylamines using oxidants such as K3Fe(CN)6, HIO3 and NaIO4 in aqueous alcohol. According to these authors, the oxidative phenylamination mechanism involves a radical cation intermediate generated by an electron transfer process from the phenylamine to the oxidant. Further electrophilic

• substitution at the 4-position of compound 1 followed by oxidation of the aminonaphthol intermediate, yield the N-phenyl-1,4-naphthoquinone-4-imines. A mechanism involving radical cation intermediates is supported by the rather high product yields resulting from the reaction of 1,5-DHN (1) with electron-donor

Homogeneous and heterogeneous photoredox-catalyzed hydroxymethylation of ketones and keto esters: catalyst screening, chemoselectivity and dilution effects

• Axel G. Griesbeck and
• Melissa Reckenthäler

Beilstein J. Org. Chem. 2014, 10, 1143–1150, doi:10.3762/bjoc.10.114

• two clearly distinguishable reaction protocols were designated as type A and B by Kisch and co-workers [12][13][14][15]. In the type A process, two different products are formed from the initially formed electron–hole pair, one from the substrate radical cation that is formed from electron transfer to

cis–trans Isomerization of silybins A and B

• Michaela Novotná,
• Radek Gažák,
• David Biedermann,
• Florent Di Meo,
• Petr Marhol,
• Marek Kuzma,
• Lucie Bednárová,
• Kateřina Fuksová,
• Patrick Trouillas and
• Vladimír Křen

Beilstein J. Org. Chem. 2014, 10, 1047–1063, doi:10.3762/bjoc.10.105

• ) and qk(N + 1) are the electronic population of atom k in its neutral, radical-cation and radical-anion forms, respectively. In this study, the Fukui function is used to partially rationalize BF3 complexation. In this case, the nucleophilic contribution is the most important parameter. It must be

The Ugi four-component reaction as a concise modular synthetic tool for photo-induced electron transfer donor-anthraquinone dyads

• Sarah Bay,
• Gamall Makhloufi,
• Christoph Janiak and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2014, 10, 1006–1016, doi:10.3762/bjoc.10.100

• constants of the solvent applied in spectroscopy (εs) and reference solvent used in electrochemistry (εref), and r+ and r− are indicating the effective ionic radii of the donor radical cation and acceptor radical anion, respectively. It is allowed to neglect the forth term, if spectroscopic and

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

• 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

• product V. Two general pathways of back-electron transfer can be followed: Path A involves one-electron reduction of the radical cation state of the catalyst. Radical chain propagation (B) can occur when the SET occurs with another molecule of the starting material I. Some attempts have been made to

Visible light mediated intermolecular [3 + 2] annulation of cyclopropylanilines with alkynes

• Theresa H. Nguyen,
• Soumitra Maity and
• Nan Zheng

Beilstein J. Org. Chem. 2014, 10, 975–980, doi:10.3762/bjoc.10.96

• % from 21. Mechanistically, the annulation with alkynes probably proceeds through a pathway similar to the one we proposed for the annulation with alkenes (Scheme 2) [29]. The photoexcited Ru(bpz)32+ oxidizes cyclopropylaniline 24 to the corresponding amine radical cation 25, which triggers the

• cyclopropyl ring opening to generate distonic radical cation 26. The primary carbon radical of 26 adds to the terminal carbon of alkyne 27 to afford vinyl radical 28. Intramolecular addition of the vinyl radical to the iminium ion of distonic radical cation 28 closes the five membered ring and furnishes amine

• radical cation 29. Finally, Ru(bpz)31+ reduces amine radical cation 29 to the annulation product 30 while regenerating Ru(bpz)32+. The proposed mechanism accounts for lower reactivity of alkynes towards intermolecular addition of nucleophilic carbon-centered radicals as well as their regiochemistry in the

Tailoring of organic dyes with oxidoreductive compounds to obtain photocyclic radical generator systems exhibiting photocatalytic behavior

• Christian Ley,
• Julien Christmann,
• Ahmad Ibrahim,
• Luciano H. Di Stefano and
• Xavier Allonas

Beilstein J. Org. Chem. 2014, 10, 936–947, doi:10.3762/bjoc.10.92

• between the dye and one of the components, for example A in Scheme 3, gives rise to a radical anion (A•−) and the oxidized PS (PS•+). Then, PS•+ can react with the electron donor D (kred) to regenerate the PS ground state (photocyclic reaction), leading to the formation of one radical cation D

Metal and metal-free photocatalysts: mechanistic approach and application as photoinitiators of photopolymerization

• Jacques Lalevée,
• Sofia Telitel,
• Pu Xiao,
• Marc Lepeltier,
• Frédéric Dumur,
• Fabrice Morlet-Savary,
• Didier Gigmes and
• Jean-Pierre Fouassier

Beilstein J. Org. Chem. 2014, 10, 863–876, doi:10.3762/bjoc.10.83

• of the radical → cation step as well as the nature of the cationic centers remains connected with the nature of eA. The key point is to find a radical directly formed through this way and that can be easily oxidized by PIC•+. Another situation is encountered in Scheme 4 where the initially formed

• Schemes, both FRP, CP and FRPCP can be initiated from the free radicals and cations generated. In these three situations, as a function of its structure, the PIC radical cation PIC•+ can behave as an initiating species. Reductible photoinitiator catalysts Scheme 5 shows a situation where the PIC is

• ][48][49][50][51][52]. The nature of the PIC is responsible for the absorption properties. Interestingly, whatever the PIC, the nature of the cation is only dependent of the choice of Add. The three-component system behaves here as an efficient dual radical/cation source. Moreover, as already known [57

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

• . For example, Kubo and coworkers [47] showed that photoreactions of N-methyl-1,2- and 2,3-naphthalimides 8 and 12 with allylsilane 9 in MeCN can produce allylation products [48][49][50][51][52] that arise by a well-known sequence involving intermolecular SET, radical cation desilylation and radical

Efficient carbon-Ferrier rearrangement on glycals mediated by ceric ammonium nitrate: Application to the synthesis of 2-deoxy-2-amino-C-glycoside

• Alafia A. Ansari,
• Y. Suman Reddy and
• Yashwant D. Vankar

Beilstein J. Org. Chem. 2014, 10, 300–306, doi:10.3762/bjoc.10.27

• mechanism The proposed mechanism of the formation of the C-allyl glycosides is shown in Scheme 1. The ring oxygen could donate an electron to the Ce3+ leading to the formation of a radical cation A. Subsequent migration of the double bond and loss of the acetyl radical could result in the formation of the