Oxidation of [3]naphthylenes to cations and dications converts local paratropicity into global diatropicity

• Abel Cárdenas,
• Zexin Jin,
• Yong Ni,
• Jishan Wu,
• Yan Xia,
• Francisco Javier Ramírez and
• Juan Casado

Beilstein J. Org. Chem. 2025, 21, 277–285, doi:10.3762/bjoc.21.20

• bonding changes. Stretching force constants were evaluated to monitor the aromatic–antiaromatic alternation pattern upon oxidation. They showed us that the dication of linear [3]naphthylene became an overall global π-electron delocalized molecule. This result was supported by nucleus independent chemical

• ] reported a stable heptacene dication in concentrated sulfuric acid, a stability attributed to the intermolecular Coulomb repulsion between the charged molecules, which prevents the dimerization of the acene. This exciting finding suggests possible modes of kinetic stabilization of oxidized species of π

• dication is associated to the appearance of a global diatropic ring current which stabilizes the whole molecule. On the contrary, 22+ can be better viewed as two segregated radical cations with slight, but high enough, local diatropic character in each. Here, we use electronic UV–vis–NIR absorption and

A review of recent advances in electrochemical and photoelectrochemical late-stage functionalization classified by anodic oxidation, cathodic reduction, and paired electrolysis

• Nian Li,
• Ruzal Sitdikov,
• Ajit Prabhakar Kale,
• Joost Steverlynck,
• Bo Li and
• Magnus Rueping

Beilstein J. Org. Chem. 2024, 20, 2500–2566, doi:10.3762/bjoc.20.214

• product (Scheme 15). The synthesis of aziridines can be achieved via the formation of nitrenes in either a metal-catalyzed or metal-free fashion. In this context, Wickens and colleagues presented a remarkable dication pool strategy for accessing N-alkylaziridines via metastable dicationic intermediates

• oxidized, either directly at the anode or by the TAC dication radical. The resulting intermediate undergoes the classic Ritter steps, reacting with acetonitrile to form a nitrile, which is subsequently hydrolyzed to yield the target amide product (Scheme 49). The construction of multiple C–O bonds from C–H

Benzylic C(sp³)–H fluorination

• Alexander P. Atkins,
• Alice C. Dean and
• Alastair J. J. Lennox

Beilstein J. Org. Chem. 2024, 20, 1527–1547, doi:10.3762/bjoc.20.137

• co-workers reported a benzylic fluorination of phenylacetic acids via a charge-transfer complex (Figure 21) [62]. The authors proposed that the combination of Selectfluor and DMAP spontaneously produced the Selectfluor radical dication (TEDA2+•), which served as a radical chain carrier capable of

• /H2O and heating, the decarboxylation pathway could be enabled to afford primary benzyl fluorides. In the same year, Barham and co-workers also showed that the radical dication TEDA2+• was capable of HAT on unactivated C(sp3)–H, enabling fluorination at these positions [63]. This work utilised para

Switchable molecular tweezers: design and applications

• Pablo Msellem,
• Maksym Dekthiarenko,
• Nihal Hadj Seyd and
• Guillaume Vives

Beilstein J. Org. Chem. 2024, 20, 504–539, doi:10.3762/bjoc.20.45

Enhanced host–guest interaction between [10]cycloparaphenylene ([10]CPP) and [5]CPP by cationic charges

• Eiichi Kayahara,
• Yoshiyuki Mizuhata and
• Shigeru Yamago

Beilstein J. Org. Chem. 2024, 20, 436–444, doi:10.3762/bjoc.20.38

• Eiichi Kayahara Yoshiyuki Mizuhata Shigeru Yamago Institute for Chemical Research, Kyoto University, Uji 611-0011, Japan 10.3762/bjoc.20.38 Abstract A dication of [5]cycloparaphenylene ([5]CPP2+) was selectively encapsulated by neutral [10]CPP to form the shortest double-layer carbon nanotube

• suggested the partial electron transfer from [10]CPP to [5]CPP2+ in the complex, and this charge-transfer (CT) interaction is most likely the origin of the higher association constant of the dicationic complex than the neutral one. Keywords: charge-transfer; cycloparaphenylene; dication; host–guest

• reported that two-electron oxidation of [n]CPPs yields dications, [n]CPPs2+ [17][21][43], which are unusually stable due to the presence of in-plane aromaticity derived from the ring structure [19]. Therefore, we speculated that the CPP dication could be used as a host or a guest to alter the electronic

Multi-redox indenofluorene chromophores incorporating dithiafulvene donor and ene/enediyne acceptor units

• Christina Schøttler,
• Kasper Lund-Rasmussen,
• Line Broløs,
• Philip Vinterberg,
• Ema Bazikova,
• Viktor B. R. Pedersen and
• Mogens Brøndsted Nielsen

Beilstein J. Org. Chem. 2024, 20, 59–73, doi:10.3762/bjoc.20.8

• Tetrathiafulvalene (TTF, Figure 1) is a redox-active molecule that has been widely explored in materials chemistry and supramolecular chemistry [1][2][3][4][5][6][7][8]. TTF reversibly undergoes two sequential one-electron oxidations, generating first a radical cation (TTF+•) and subsequently a dication (TTF2

Cyclization of 1-aryl-4,4,4-trichlorobut-2-en-1-ones into 3-trichloromethylindan-1-ones in triflic acid

• Vladislav A. Sokolov,
• Andrei A. Golushko,
• Irina A. Boyarskaya and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2023, 19, 1460–1470, doi:10.3762/bjoc.19.105

• in species Ca leading to dication Aa is thermodynamically unfavorable (ΔG298 = 68 kJ/mol) as well (see overview scheme of Table 3). NMR experiments allowed us to observe the formation of O,O-diprotonated species in the superacid TfOH (Table 2). The dication Aa should not be transformed to species Da

• analogously to cation Ba. The cyclization of dication Aa into indanone 3a is very favorable (ΔG298 = −101.3 kJ/mol). However, the formation of both enones 2 and indanones 3 from hydroxy ketones 1 is observed in TfOH (Table 1). We assume that, at first, hydroxy ketones 1 undergo dehydration into enones 2

Photoredox catalysis harvesting multiple photon or electrochemical energies

• Mattia Lepori,
• Simon Schmid and
• Joshua P. Barham

Beilstein J. Org. Chem. 2023, 19, 1055–1145, doi:10.3762/bjoc.19.81

Synthesis, structure, and properties of switchable cross-conjugated 1,4-diaryl-1,3-butadiynes based on 1,8-bis(dimethylamino)naphthalene

• Semyon V. Tsybulin,
• Ekaterina A. Filatova,
• Alexander F. Pozharskii,
• Valery A. Ozeryanskii and
• Anna V. Gulevskaya

Beilstein J. Org. Chem. 2023, 19, 674–686, doi:10.3762/bjoc.19.49

• (Scheme 5). Presumably, when R = H or OMe, structure 17 contributes the most to the resonance hybride, while in cases of molecules 5d,e with π-acceptor substituents, a dication of type 18 better describes the electron density distribution. The only exception is the trifluoromethyl derivative 5с, which

Total synthesis of insect sex pheromones: recent improvements based on iron-mediated cross-coupling chemistry

• Eric Gayon,
• Guillaume Lefèvre,
• Olivier Guerret,
• Adrien Tintar and
• Pablo Chourreu

Beilstein J. Org. Chem. 2023, 19, 158–166, doi:10.3762/bjoc.19.15

• ligand to the iron center in alkyl–alkenyl cross-coupling reactions featuring Grignard reagents, but was involved in the formation of the bulky dication [Mg(NMP)6]2+, the presence of the latter contributing to the kinetic stabilization of the on-cycle active species [Me3FeII]− (Table 2, entry 1) [35

Redox-active molecules as organocatalysts for selective oxidative transformations – an unperceived organocatalysis field

• Elena R. Lopat’eva,
• Igor B. Krylov,
• Dmitry A. Lapshin and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2022, 18, 1672–1695, doi:10.3762/bjoc.18.179

• perform the CH-functionalization of alkanes by electron-deficient alkenes. Photoredox catalysis was employed for the one-electron oxidation of the DABCO-derived organocatalyst to the dication radical. The authors noted that the introduction of a substituent X near the radical center further improves the

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

• Figure 9, for the generation of a radical cation and dication at half-wave potential values of +0.65 V (ΔEp = 0.05 V) and +0.87 V (ΔEp = 0.06 V), respectively. Two reduction waves, corresponding to the radical anion and dianion, can be seen at the half-wave potentials of −1.51 V (ΔEp = 0.06 V) and −1.64

• V (ΔEp = 0.06 V), respectively. UV–vis absorption spectroelectrochemistry (see Figures S20 and S21 in Supporting Information File 1) shows the evolution of the dication and dianion states with the longest wavelength absorption band extending into the near-IR with broad features, characteristic of

Synthesis of 5-arylacetylenyl-1,2,4-oxadiazoles and their transformations under superelectrophilic activation conditions

• Andrey I. Puzanov,
• Dmitry S. Ryabukhin,
• Anna S. Zalivatskaya,
• Dmitriy N. Zakusilo,
• Darya S. Mikson,
• Irina A. Boyarskaya and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2021, 17, 2417–2424, doi:10.3762/bjoc.17.158

• protonation of 5-acetylenyl-1,2,4-oxadiazoles 3 (Table 1), one would propose the following reaction pathways for compounds 3 in Brønsted superacids (Scheme 2). Protonation of oxadiazole 3 affords dication B, which may react with counter anion of acid X− giving rise to vinyl derivatives 4. In the presence of

CF₃-substituted carbocations: underexploited intermediates with great potential in modern synthetic chemistry

• Anthony J. Fernandes,
• Armen Panossian,
• Bastien Michelet,
• Agnès Martin-Mingot,
• Frédéric R. Leroux and
• Sébastien Thibaudeau

Beilstein J. Org. Chem. 2021, 17, 343–378, doi:10.3762/bjoc.17.32

• electrophiles [101]) generated in superacid media [102]. Hence, when trifluoroacetyl pyridine 156 was treated with benzene in triflic acid, alcohol derivative 157 was obtained. In a superacid, 156 generates a dication 158 in which the electrophilicity is enhanced through a strong charge repulsion (Scheme 39

• ). This dication reacts with benzene to provide pyridinium–oxonium dication 159 in solution. Further arylation does not occur spontaneously, which was evident because alcohol 157 was isolated at the end of the reaction. Upon heating at 60 °C, the second arylation takes place, presumably via the formation

[1,3]/[1,4]-Sulfur atom migration in β-hydroxyalkylphosphine sulfides

• Katarzyna Włodarczyk,
• Piotr Borowski and
• Marek Stankevič

Beilstein J. Org. Chem. 2020, 16, 88–105, doi:10.3762/bjoc.16.11

• , affording intermediate IV, which may undergo two different transformations: The first transformation involves dissociation of a water molecule, which leads to the formation of the dication IX through transition state VIII. Taking into account that all energy barriers were well below 10 kcal/mol, it seemed

• that this transformation was reversible, and therefore the dication IV may have entered an alternative pathway, which involved the rotation of the molecule around the Cα–Cβ bond (activation barrier: +5.4 kcal/mol, stabilization: −3.4 kcal/mol), which was feasible under the reaction conditions. The

• formed dication V underwent an intramolecular nucleophilic substitution through transition state VI, which proceeded with a small activation barrier, leading to the cyclic intermediate VII and further to the rearranged product 54. The tentative mechanism discussed above does not explain the formation of

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

• +. The generation of the dication agreed with the decrease in the IVCT intensity. The IVCT band of 1b+ was fitted using a Gaussian function (Figure 5) to obtain the spectroscopic parameters of energy (υmax), intensity (ε), and bandwidth at the half-height (Δυ1/2) (Table 2). An electronic coupling for 1b

• ferrocenium moiety is accommodated largely on the d orbital, while that of the NAr3•+ moiety is delocalized from the nitrogen center to the benzene ring adjacent to the urea bridge. The MV species 1a+ and the dication 1a2+ were also generated by the controlled-potential electrolysis and characterized by UV

1,2,3,4-Tetrahydro-1,4,5,8-tetraazaanthracene revisited: properties and structural evidence of aromaticity loss

• Arnault Heynderickx,
• Sébastien Nénon,
• Olivier Siri,
• Vladimir Lokshin and
• Vladimir Khodorkovsky

Beilstein J. Org. Chem. 2019, 15, 2059–2068, doi:10.3762/bjoc.15.203

• charge along the both conjugated moieties (Table 1). The bonds of C1–C6 (1.469 Å) and C8–C13 (1.441 Å) are also elongated, indicating further loss of aromaticity within the dication. The planarity distortion is smaller than observed in 3, judging by the torsion angles C7–C6–C1–C14 and C7–C8–C13–C14

• . For instance, the energy difference between the dication 6 and a hypothetic dication with protonated amino groups is 51 kcal/mol in favor of 6. UV–vis absorption spectra In solution, 3 is characterized by a strong absorption band, at 402 nm (toluene), 406 nm (acetone), 413 nm (water) and 422 nm

• electronic transitions are involved (Supporting Information File 1, Figure S2). Protonation of 3 with acids (HCl or HBF4 in ethanol) occurs in two separate steps (Figure 6) and the formation of the dication requires an excess of the acid. The dropwise addition of the acid to the solution of 3 gives rise to

Reactions of 2-carbonyl- and 2-hydroxy(or methoxy)alkyl-substituted benzimidazoles with arenes in the superacid CF₃SO₃H. NMR and DFT studies of dicationic electrophilic species

• Dmitry S. Ryabukhin,
• Alexey N. Turdakov,
• Natalia S. Soldatova,
• Mikhail O. Kompanets,
• Alexander Yu. Ivanov,
• Irina A. Boyarskaya and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2019, 15, 1962–1973, doi:10.3762/bjoc.15.191

• electrophilicity indices ω of 4.4 and 4.9 eV, respectively, compared to cations III, V, VII, and VIII with ω values of 2.1–2.2 eV. Among all studied species, the heteroaromatic benzyl dication IV, VI, IX have the highest electrophilicity indices ω = 5.6–6.1 eV (Table 1). In the dications I and II, the carbon Cα

Superelectrophilic carbocations: preparation and reactions of a substrate with six ionizable groups

• Sean H. Kennedy,
• Makafui Gasonoo and
• Douglas A. Klumpp

Beilstein J. Org. Chem. 2019, 15, 1515–1520, doi:10.3762/bjoc.15.153

• superelectrophilic reactivity [1][2][3][4][5]. Examples of superelectrophiles include the nitronium dication (1) and the acetylium dication (2, Scheme 1). Both of these species have been proposed as superelectrophilic intermediates in the reactions of nitronium (NO2+) and acetylium (CH3CO+) salts in superacids. In

• sufficiently acidic media, cationic electrophiles such as the nitronium ion may undergo protonation, leading to the nitronium dication (1), and a greatly enhanced electrophilic reactivity. In superacidic solutions, nitronium salts have been shown to react with deactivated arenes and saturated hydrocarbons

Cyclobutane dication, (CH₂)₄²⁺: a model for a two-electron four-center (2e-4c) Woodward–Hoffmann frozen transition state

• G. K. Surya Prakash and
• Golam Rasul

Beilstein J. Org. Chem. 2019, 15, 1475–1479, doi:10.3762/bjoc.15.148

• G. K. Surya Prakash Golam Rasul Loker Hydrocarbon Research Institute and Department of Chemistry, University of Southern California, University Park, Los Angeles, CA 90089-1661, USA 10.3762/bjoc.15.148 Abstract The structures of the elusive cyclobutane dication, (CH2)42+, were investigated at the

• considered as a prototype for a 2e-4c Woodward–Hoffmann frozen transition state. The planar rectangular shaped structure 2 with a 2e-4c bond was found not to be a minimum. Keywords: cyclobutane dication; 2e-4c bond; frozen transition state; Woodward–Hoffmann rule; Introduction The protonated hydrogen

• . This type of bonding could occur in rigid frameworks such as in 1,3-dehydro-5,7-adamantanediyl dication (iii) [7] and pagodane dication (iv) [8]. The question is can a 2e-4c bond exist in a molecular structure involving four atoms without any rigid frameworks such as in the diprotonated hydrogen (H42

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

• process of 1 is almost reversible but induces to some extent an irreversible oxidation process that shows up as further reduction half wave in the cyclic voltammogram. This is true for almost all synthesized derivatives 3–9. The radical dication is known to undergo disproportionation reactions [27], which

1,8-Bis(dimethylamino)naphthyl-2-ketimines: Inside vs outside protonation

• A. S. Antonov,
• A. F. Pozharskii,
• P. M. Tolstoy,
• A. Filarowski and
• O. V. Khoroshilova

Beilstein J. Org. Chem. 2018, 14, 2940–2948, doi:10.3762/bjoc.14.273

• ΔE = Eb’ – Eb (kcal/mol) for different sites of protonation of the studied imines (B3LYP/6-311+G(d,p)). Molecular structure of protonated imines 4a·HClO4 (a) and 6b·EtOH (b). C=NH2+ Signal regions of temperature-depending spectra for compounds 4c–7c, acetone-d6. Molecular structure of dication 6с

Generation of 1,2-oxathiolium ions from (arysulfonyl)- and (arylsulfinyl)allenes in Brønsted acids. NMR and DFT study of these cations and their reactions

• Stanislav V. Lozovskiy,
• Alexander Yu. Ivanov,
• Olesya V. Khoroshilova and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2018, 14, 2897–2906, doi:10.3762/bjoc.14.268

• large positive charge in cations A, B. For dication Bh, different signals were detected for quaternary carbons C5 and C5', and vinyl carbons C4 and C4', etc., that, probably, indicates formation of two diastereomers (one meso-form and one pair of enantiomers) due to the stereogenic sulfur centers. In

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

• dication C2+ (Figure 2d, green), as indicated by the hypsochromic shift due to the absence of an open-shell system. The formed dication exhibits characteristic absorption bands centered at 493 nm and 621 nm, identical to the species formed upon oxidation of the open isomers. Notably, while the first

• reduction, a species analogous to FP was not observed (vide infra and Figure S43, Supporting Information File 1). Considering all these findings, a mechanism for the oxidative cyclization of sDTE66-Me (Scheme 3) can be derived: Starting from either open isomer fast isomerization to the same dication C2

• + takes place upon oxidation. Both, the isomerization of the double bond of the E-isomer as well as the cyclization reaction are instantaneous on the timescale of the experiment. The closed dication C2+ can be reduced stepwise to its neutral form. In addition, when C2+ is not stabilized by donor

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

• radical cation or dication. For over 20 years, TTFs have been key building blocks for the construction of redox-switchable mechanically interlocked molecules (MIMs) and their electrochemical operation has been thoroughly investigated. In this review, we provide an introduction into the field of TTF-based

• molecular switch. A first one-electron oxidation [23] converts neutral TTF (1) into the radical-cationic species 1●+ (Figure 1). The TTF radical cation is one of the rare organic radicals that are long-term stable and even isolable. A second oxidation step yields the dication 12+. Both redox-transitions are

• widely used to induce cofacial intermolecular stacking interactions. Finally, the TTF2+ dication adopts a twisted conformation with D2 symmetry. In the neutral state, TTF is a strong π-donor molecule, a property which is used in a plethora of charge-transfer materials and molecules [27]. In