Electrochemical synthesis of cyclic biaryl λ³-bromanes from 2,2’-dibromobiphenyls

• Andrejs Savkins and
• Igors Sokolovs

Beilstein J. Org. Chem. 2025, 21, 451–457, doi:10.3762/bjoc.21.32

• substrates that do not form the desired electrochemical oxidation product see Supporting Information File 1, Scheme S1). A series of control experiments was performed to rationalize the observed reactivity trends (Scheme 2). The measured redox potentials EP/2 for 2,2'-dibromo-1,1'-biphenyls 4a–g (from 1.77 V

• developed method represents a safe and inexpensive alternative to the commonly used thermal decomposition of potentially explosive diazonium salts. The successful electrochemical oxidation requires the presence of two chelating ester groups that stabilize the formed Br(III) species. Further work towards

• : Representative jp vs v0.5 slope values for oxidation of Martin’s bromane precursor 6 (ref. [17]). D: Plausible reaction mechanism. Optimization of electrochemical oxidation/cyclization conditions.a Supporting Information Crystallographic data for the structure reported in this paper have been deposited with the

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

• oxidized species of compounds 1 and 2 are shown in Figure 3. Initial electrochemical oxidation of 1 resulted in the progressive replacement of its absorption bands by three new features, which were assigned to the 1•+ radical cation, namely at 352/369 nm, a multiplet in the 500–600 nm interval, and a broad

• , Me: methyl). Cyclic voltammograms of 1 and 2. UV–vis–NIR electronic absorption spectra of 1 (top) and 2 (bottom) during the electrochemical oxidation in 0.1 M n-Bu4N·PF6 in CH2Cl2 at room temperature. The traces are black lines for neutral, blue lines for radical cation, and red lines for dication

Synthesis of disulfides and 3-sulfenylchromones from sodium sulfinates catalyzed by TBAI

• Zhenlei Zhang,
• Ying Wang,
• Xingxing Pan,
• Manqi Zhang,
• Wei Zhao,
• Meng Li and
• Hao Zhang

Beilstein J. Org. Chem. 2025, 21, 253–261, doi:10.3762/bjoc.21.17

• catalysts in conjunction with oxygen [17][18][19][20][21][22], electrochemical oxidation [23][24], and photochemical oxidation techniques [25] have emerged as alternative methods. However, these approaches have a significant limitation: the substrates must be thiols, which have unpleasant odors. This has

Recent advances in electrochemical copper catalysis for modern organic synthesis

• Yemin Kim and
• Won Jun Jang

Beilstein J. Org. Chem. 2025, 21, 155–178, doi:10.3762/bjoc.21.9

• electrochemical oxidation. In contrast, the naphthyl-substituted Schiff base generated the corresponding enantioenriched product 36 through 1,4-addition followed by intramolecular annulation. When 2,6-disubstituted hydroquinone was used as the starting material, 1,6-addition occurred due to steric hindrance

• . Accordingly, the formation of the Cu(II) iminyl complex 65 promotes the electrochemical oxidation of Cu(III) iminyl complex 66, which then dissociates to generate the iminyl radical 67. Finally, the iminyl radical delivers the quinoxaline product 59 via radical annulation, followed by rearomatization through

Hypervalent iodine-mediated intramolecular alkene halocyclisation

• Charu Bansal,
• Oliver Ruggles,
• Albert C. Rowett and
• Alastair J. J. Lennox

Beilstein J. Org. Chem. 2024, 20, 3113–3133, doi:10.3762/bjoc.20.258

• fluorinated oxazolines 32 was also reported using an electrochemical approach in 2019 by Waldvogel and co-workers (Scheme 17) [40]. The authors used electrochemical oxidation to form p-tolyl-difluoro-λ3-iodane 10 on the anode using an undivided cell with platinium electrodes in a 1:1 solution of CH2Cl2 and

• electrochemical oxidation of the substrate. A range of N-allylcarboxamides 31 were cyclised to fluorinated oxazolines 32 in moderate to very good yields. Poor yields, however, were reported with electron-withdrawing aryl groups on the substrate. Intramolecular nucleophilic attack from oxygen onto the activated

• via electrochemical oxidation of 4-iodotoluene at the anode, in a 5:6 HF:amine mixture to cyclise a range of phenolic ethers 33. Tolerance for substituents on both the aromatic ring and the alkene were shown, although the electronic requirements were quite narrow for reaction success. As the arene

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

• . For example, Liu and colleagues demonstrated the electrochemical oxidation of benzylic C–H bonds to ketones using tert-butyl hydroperoxide as the radical initiator [14]. This method was applied to functionalize bioactive molecules, with celestolide, ibuprofen methyl ester, and papaverine being

• oxidized at the benzylic position in good yields. A gram-scale test was conducted to confirm the potential for large-scale applications. According to the authors, the electrochemical oxidation of t-BuOOH at the anode leads to a tert-butyl peroxyl radical that activates the C–H bond at the benzylic position

• ]. This mild method proceeds with a broad range of unactivated alkenes, including natural products and pharmaceutical derivatives such as sulbactam acid and oxaprozin. Mechanistic studies revealed that the reaction was initiated by the electrochemical oxidation of iodide ions, generating iodine radicals

Efficient one-step synthesis of diarylacetic acids by electrochemical direct carboxylation of diarylmethanol compounds in DMSO

• Hisanori Senboku and
• Mizuki Hayama

Beilstein J. Org. Chem. 2024, 20, 2392–2400, doi:10.3762/bjoc.20.203

• (Table 1, entry 6). In contrast, zinc was not effective as an anode material in the carboxylation, probably due to competitive electrochemical reduction of zinc ions generated by electrochemical oxidation of the zinc anode. The deposition of a black precipitate was observed visually at the cathode (Table

• competitively occurs at the cathode, and an excess amount of electricity should therefore be necessary to obtain acceptable results. At the anode, on the other hand, dissolution of magnesium ions by electrochemical oxidation of magnesium metal occurs, preventing electrochemical oxidation of the product and

gem-Difluorination of carbon–carbon triple bonds using Brønsted acid/Bu₄NBF₄ or electrogenerated acid

• Mizuki Yamaguchi,
• Hiroki Shimao,
• Kengo Hamasaki,
• Keiji Nishiwaki,
• Shigenori Kashimura and
• Kouichi Matsumoto

Beilstein J. Org. Chem. 2024, 20, 2261–2269, doi:10.3762/bjoc.20.194

• University, 3-4-1 Kowakae, Higashi-osaka, Osaka, 577-8502, Japan 10.3762/bjoc.20.194 Abstract gem-Difluorination of carbon–carbon triple bonds was conducted using Brønsted acids, such as Tf2NH and TfOH, combined with Bu4NBF4 as the fluorine source. The electrochemical oxidation of a Bu4NBF4/CH2Cl2 solution

• −’’ equivalents might serve as good reagents for the gem-difluorination of alkynes. Thus, we have examined the electrochemical oxidation of a solution of Bu4NBF4/CH2Cl2 containing 1a (0.5 mmol) in a divided cell using 8 mA or 16 mA (Scheme 1, method B, in-cell method). In-cell method means that EGA was generated

• analysis in the case of 16 mA [53]. With the successful formation of (5,5-difluorohexyl)benzene (2a) by the chemical (method A) and electrochemical oxidation (method B) methods in hand, we have investigated the scope and limitations of gem-difluorination for various alkynes (Table 2). Electrochemical

Harnessing the versatility of hydrazones through electrosynthetic oxidative transformations

• Aurélie Claraz

Beilstein J. Org. Chem. 2024, 20, 1988–2004, doi:10.3762/bjoc.20.175

• hydrazone (Scheme 20). Initial SET oxidation of the hydrazone In 1973, Barbey and Caullet have shown that the benzaldehyde-derived N,N-diphenylhydrazone 107 dimerized upon electrochemical oxidation on platinum electrode [68]. The following year, they demonstrated that in the presence of an excess of

• electrochemical synthesis of diazo compounds from hydrazones. Transformations involving diazo compounds as either products or intermediates are covered. While investigating the electrochemical oxidation of benzophenone hydrazones 130, Chiba et al. discovered that several products were obtained depending on the

• platinum cathode materials at 55 °C with a minimal amount of sodium methoxide, thereby limiting side products formation such as 133–135 or some oligomers of ethylenes (Scheme 28) [77]. In 2002, Okimoto et al. reported the indirect electrochemical oxidation of benzilhydrazones 138 using potassium iodide as

Novel oxidative routes to N-arylpyridoindazolium salts

• Oleg A. Levitskiy,
• Yuri K. Grishin and
• Tatiana V. Magdesieva

Beilstein J. Org. Chem. 2024, 20, 1906–1913, doi:10.3762/bjoc.20.166

• oxidation of both N-centers was demonstrated in [19]. The wide variety of the subsequent reaction channels for the radical cations formed under chemical or electrochemical oxidation of diarylamines, as well as availability of variously substituted diarylamines make them perspective starting compounds for

• the post-electrolysis mixture. Instead, a complex mixture of products was obtained. It looks as if the oxidation is non-selective; not a single reaction path dominates. This is typical for diarylamines containing electron-withdrawing substituents in both rings; commonly, electrochemical oxidation

Oxidative fluorination with Selectfluor: A convenient procedure for preparing hypervalent iodine(V) fluorides

• Samuel M. G. Dearman,
• Xiang Li,
• Yang Li,
• Kuldip Singh and
• Alison M. Stuart

Beilstein J. Org. Chem. 2024, 20, 1785–1793, doi:10.3762/bjoc.20.157

• stability and is highly hygroscopic, it is often prepared in situ and Gilmour [3][4][5][6][7][8] has reported a range of fluorination protocols utilising hypervalent iodine(I/III) catalysis (Scheme 1A). Lennox has also demonstrated that 1 can be generated cleanly by electrochemical oxidation [9][10]. In an

Synthesis of polycyclic aromatic quinones by continuous flow electrochemical oxidation: anodic methoxylation of polycyclic aromatic phenols (PAPs)

• Hiwot M. Tiruye,
• Solon Economopoulos and
• Kåre B. Jørgensen

Beilstein J. Org. Chem. 2024, 20, 1746–1757, doi:10.3762/bjoc.20.153

• Chemistry, Norwegian University of Science and Technology, 7491 Trondheim, Norway 10.3762/bjoc.20.153 Abstract The electrochemical oxidation of polycyclic aromatic phenols (PAPs) has been developed in a microfluidic cell to synthesize polycyclic aromatic quinones (PAQs). Methanol was used as nucleophile to

• alternative to classical synthesis [25][26][27][28]. Electrochemical oxidation reactions are further used to emulate enzymatic oxidations of drugs and explore potential metabolites [29][30][31]. Electrochemical flow systems provide fast electrosynthesis with low cell resistance, large electrode area, and good

• control of the current [32][33][34]. Early studies on the electrochemical oxidation of phenols revealed that the oxidation passes through a phenoxonium ion and forms acetals in methanol but quinones in the presence of water [35][36][37]. However, the reaction is sometimes accompanied by the formation of

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

• of C(sp3)–H activation and fluorination, including on one tertiary and five secondary benzylic substrates (Figure 14) [54]. This work utilised electrochemical oxidation with a nucleophilic source of fluoride, CsF, to regenerate the trisligated copper(III) fluoride complex. In 2016, Silas reported an

• and oxidation potentials. Electrochemical methods Synthetic electrochemistry is a powerful tool offering excellent control over reaction kinetics and selectivity [86]. Electrochemical oxidation has been demonstrated as an efficient means for generating benzylic cations, allowing for the introduction

• ). Overall, this work demonstrates the broadest range of secondary and tertiary benzylic substrates for electrochemical nucleophilic fluorination. As highlighted by the previous examples, electrochemical oxidation is a useful tool for preparing benzylic fluorides. However, a number of reports highlight the

Synthetic applications of the Cannizzaro reaction

• Bhaskar Chatterjee,
• Dhananjoy Mondal and
• Smritilekha Bera

Beilstein J. Org. Chem. 2024, 20, 1376–1395, doi:10.3762/bjoc.20.120

• a competing Cannizzaro reaction during the electrochemical oxidation of furfural [60]. On the other hand, 5-hydroxymethyl-2-furancarboxylic acid (HMFCA) and dihydroxymethylfuran (DHMF), obtained via the Cannizzaro disproportionation of 5-(hydroxymethyl)furfural, were electrochemically oxidized to

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

Synthesis of π-conjugated polycyclic compounds by late-stage extrusion of chalcogen fragments

• Aissam Okba,
• Pablo Simón Marqués,
• Kyohei Matsuo,
• Naoki Aratani,
• Hiroko Yamada,
• Gwénaël Rapenne and
• Claire Kammerer

Beilstein J. Org. Chem. 2024, 20, 287–305, doi:10.3762/bjoc.20.30

• synthesized thiepine-containing polymers designed to undergo redox-driven bent-to-planar conformational changes [63]. However, upon electrochemical oxidation of the drop-cast film of polymer 13, the authors observed the conversion of the dithienobenzothiepine monomeric units into dithienonaphthalenes, which

• dithienonaphthalenes, upon S-extrusion triggered by electrochemical oxidation. Bottom: Exploitation of the S-extrusion process for peroxide sensing, taking advantage of the lability of oxidized dithienobenzothiepine to generate highly fluorescent dithienonaphthalene [63]. Synthesis of S-doped extended triphenylene

Additive-controlled chemoselective inter-/intramolecular hydroamination via electrochemical PCET process

• Kazuhiro Okamoto,
• Naoki Shida and
• Mahito Atobe

Beilstein J. Org. Chem. 2024, 20, 264–271, doi:10.3762/bjoc.20.27

• . Electrochemical oxidation of 1 under varying conditions. Supporting Information Supporting Information File 18: Detailed experimental procedures, CV simulation, copies of NMR spectra. Funding This work was supported by JSPS KAKENHI (Grant Nos. 22K18915 and 21H05215 to M.A. and 22H02118 23K17370, and 23H04916 to

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

A new oxidatively stable ligand for the chiral functionalization of amino acids in Ni(II)–Schiff base complexes

• Alena V. Dmitrieva,
• Oleg A. Levitskiy,
• Yuri K. Grishin and
• Tatiana V. Magdesieva

Beilstein J. Org. Chem. 2023, 19, 566–574, doi:10.3762/bjoc.19.41

• dimerization of the Schiff base complex and the radical cation formed under one-electron electrochemical oxidation will be sufficiently stable, opening a route to further oxidative modification of the amino acid side chain under appropriate conditions. Additionally, this bulky group may significantly alter the

• the following problems. First of all, radical cations formed under a one-electron electrochemical oxidation of the glycine and dehydroalanine complexes become sufficiently stable. The fast side reaction of the oxidative dimerization of the Schiff base complex via the phenylene fragments (inherent to

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

• high hydrogen binding energy and low deprotonation free energy. N-Ammonium ylides were used for the electrochemical oxidation of unactivated C–H bonds (Scheme 37). Ylides showed good selectivity and an unusual reactivity pattern in comparison with known mediators for CH-oxidation. For example, a

• electrochemical oxidation of primary alcohols and aldehydes to carboxylic acids. Electrocatalytic oxidation of benzylic alcohols by a TEMPO derivative immobilized on a graphite anode by π–π stacking interactions. Electrochemical oxidation of carbamates of cyclic amines to lactams and oxidative cyanation of amines

Electrochemical Friedel–Crafts-type amidomethylation of arenes by a novel electrochemical oxidation system using a quasi-divided cell and trialkylammonium tetrafluoroborate

• Hisanori Senboku,
• Mizuki Hayama and
• Hidetoshi Matsuno

Beilstein J. Org. Chem. 2022, 18, 1040–1046, doi:10.3762/bjoc.18.105

• , Hokkaido 060-8628, Japan 10.3762/bjoc.18.105 Abstract Electrochemical Friedel–Crafts-type amidomethylation was successfully carried out by a novel electrochemical oxidation system using a quasi-divided cell and trialkylammonium tetrafluoroborates, such as iPr2NHEtBF4. Constant current electrolysis of

• amidomethylated products in good to high yields. Keywords: electrochemical oxidation; Friedel–Crafts type amidomethylation; N-acyliminium ion; quasi-divided cell; trialkylammonium salt; Introduction Oxidation of amides generates useful intermediates, N-acyliminium ions, which have been widely used in organic

• necessary in some cases (path b in Scheme 1) [14][15]. On the other hand, N-acyliminium ions can easily be generated by electrochemical oxidation without those reagents. Electrochemical oxidation of amides/carbamates yielding N-acyliminium ions is well known as Shono oxidation (path c in Scheme 1) [16] and

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

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

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

• , we compare these two crown ethers, their smaller analogs and add a two TTF-units containing crown ether bisTTFC8, which was previously synthesized by Becher and co-workers [41]. These TTF-containing crown ethers become positively charged upon electrochemical oxidation, resulting in Coulomb repulsion

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

• from the electrochemical oxidation (Scheme 26C). When the ketals were not fused to a central ring, the least-hindered C(sp3)–H bond reacted, as in the products 61 and 62. When the ketals were fused to a central ring, as in galactose acetonide, the C2 position underwent a selective C(sp3)–H fluorination