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

Active-metal template clipping synthesis of novel [2]rotaxanes

• Cătălin C. Anghel,
• Teodor A. Cucuiet,
• Niculina D. Hădade and
• Ion Grosu

Beilstein J. Org. Chem. 2023, 19, 1776–1784, doi:10.3762/bjoc.19.130

• macrocycles are more shifted, with the triazole proton presenting an upfield shift from δ = 7.95 ppm to δ = 7.65 ppm and the hydroquinone protons are upfield shifted from δ = 6.77/6.67 ppm to δ = 6.60/6.58 ppm. In order to validate formation of R1 we also recorded a room-temperature H,H-ROESY NMR spectrum

Enabling artificial photosynthesis systems with molecular recycling: A review of photo- and electrochemical methods for regenerating organic sacrificial electron donors

• Grace A. Lowe

Beilstein J. Org. Chem. 2023, 19, 1198–1215, doi:10.3762/bjoc.19.88

• photosynthesis. It is also noteworthy that the reduced pyridinium compounds resemble Hantzsch esters which are organic reductants commonly used in organic synthesis. Quinones and hydroquinones have also been used in RFBs. Notably, 1,4-hydroquinone and 1,4-benzoquinone were used to create membrane-less RFBs with

• ITIES and charge-separation maintained in a flowing system [67][68]. Two of the examples shown in Figure 4 AQDS (0.46 V vs SCE at pH 0) and hydroquinone sulfate (0.89 V vs SCE at pH 0.7) have been used as hydrogen carriers in decoupled water splitting, rather than in RFBs [57]. Hydrogen carriers in

• reductive quenching of Ru(bpy)3 and reduction of photooxidized Ru(bpy)3. Furthermore, quinones have well-studied PCET chemistry [26]. 2,3-Dichloro-5,6-cyano-1,4,hydroquinone, the hydrogenated form of 2,3-dichloro-5,6-cyano-1,4-benzoquinone (DDQ), has the highest oxidation potential of the 3 quinone examples

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

Aromatic C–H bond functionalization through organocatalyzed asymmetric intermolecular aza-Friedel–Crafts reaction: a recent update

• Anup Biswas

Beilstein J. Org. Chem. 2023, 19, 956–981, doi:10.3762/bjoc.19.72

• antibacterial acitivity against resistant S. aureus strains. It is also an inhibitor of the enzyme peptide deformylases (PDFs). The synthesis comprised the reaction between the highly substituted hydroquinone 142 and dehydroalanine 143 in the presence of chiral phosphoric acid P7 as catalyst to prepare

Combining the best of both worlds: radical-based divergent total synthesis

• Kyriaki Gennaiou,
• Antonios Kelesidis,
• Maria Kourgiantaki and
• Alexandros L. Zografos

Beilstein J. Org. Chem. 2023, 19, 1–26, doi:10.3762/bjoc.19.1

• , comprising one of the most concise methods to attain this class of compounds, highlighting the power of merged biocatalytic and radical tactics [32]. (+)-Yahazunol (61) and related meroterpenoids (Li 2018) [33]: In 2018, Li’s group reported a divergent plan for the synthesis of drimane-type hydroquinone

• meroterpenoids. This class of compounds possesses versatile bioactivities, ranging from anticancer and anti-HIV to antifungal properties, with minor modifications on the decoration of either the hydroquinone or the terpene part of the secondary metabolite [34]. The group applied a semisynthetic plan starting

• chemoenzymatic and radical synthesis (part II, Renata). Divergent synthesis of drimane-type hydroquinone meroterpenoids (Li). Divergent synthesis of natural products isolated from Dysidea avara (Lu). Divergent synthesis of kaurene-type terpenoids (Lei). Divergent synthesis of 6-oxabicyclo[3.2.1]octane

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

• -tetrachloro-1,4-benzoquinone (p-chloranil). In a typical catalytic cycle, the quinone molecule performs two-electron oxidation to form the hydroquinone, which is then reoxidized by terminal oxidants (Scheme 25). However, radical semiquinone intermediates can also be formed and participate in the oxidation of

Rhodium-catalyzed intramolecular reductive aldol-type cyclization: Application for the synthesis of a chiral necic acid lactone

• Motoyuki Isoda,
• Kazuyuki Sato,
• Kenta Kameda,
• Kana Wakabayashi,
• Ryota Sato,
• Hideki Minami,
• Yukiko Karuo,
• Atsushi Tarui,
• Kentaro Kawai and
• Masaaki Omote

Beilstein J. Org. Chem. 2022, 18, 1642–1648, doi:10.3762/bjoc.18.176

• to the literature, a Sharpless dihydroxylation of benzyl tiglate (8) to form a chiral diol 9 was followed by a Parikh–Doering oxidation to give the corresponding product 10 in 62% yield (Scheme 4) [58][59]. Subsequent acryloylation in the presence of DMAP and hydroquinone gave the intramolecular

• , Et3N, acryloyl chloride, hydroquinone. d) [RhCl(cod)]2, THF, Et2Zn. Optimization of the reaction conditions. Supporting Information Supporting Information File 308: General procedures and analytical data, including copies of 1H NMR, 13C NMR, and X-ray crystallography. Acknowledgements We would like

Microelectrode arrays, electrosynthesis, and the optimization of signaling on an inert, stable surface

• Kendra Drayton-White,
• Siyue Liu,
• Yu-Chia Chang,
• Sakashi Uppal and
• Kevin D. Moeller

Beilstein J. Org. Chem. 2022, 18, 1488–1498, doi:10.3762/bjoc.18.156

• complex molecule, the synthesis of a complex, two-dimensional addressable surface requires a new type of selectivity – "site-selectivity". The use of electrosynthesis is essential for obtaining this selectivity. With the substrate on the surface of the array, a hydroquinone/quinone redox couple was then

• used for the subsequent signaling experiment [20]. The hydroquinone/quinone redox couple has superior stability to the iron-based systems used previously [20], and its use leads to more reproducible binding curves. To generate the binding curve shown in Figure 4, the concentration of the integrin

• for the placement reaction. The "binding curves" generated at the electrodes with these two placement times were compared with the background signal derived from the unfunctionalized polymer. The more stable (relative to iron-based mediator pairs) hydroquinone/quinone redox pair was used, again in

Automated grindstone chemistry: a simple and facile way for PEG-assisted stoichiometry-controlled halogenation of phenols and anilines using N-halosuccinimides

• Dharmendra Das,
• Akhil A. Bhosle,
• Amrita Chatterjee and
• Mainak Banerjee

Beilstein J. Org. Chem. 2022, 18, 999–1008, doi:10.3762/bjoc.18.100

•  3). Once again, no prominent substituent effect was observed in terms of yields or reaction time. Next, we focused our attention on expanding the substrate scope to other electron-rich aromatic systems. The bromination of hydroquinone dimethyl ether was sluggish and a moderate yield (67%) of the

BINOL as a chiral element in mechanically interlocked molecules

• Matthias Krajnc and
• Jochen Niemeyer

Beilstein J. Org. Chem. 2022, 18, 508–523, doi:10.3762/bjoc.18.53

• containing electron-rich hydroquinone or 1,5-dioxynaphthalene units (macrocycles 15/21/23), together with suitable dicationic bis-bipyridinium precursors (16/19). Self-assembly of the corresponding pseudorotaxanes by π–π stacking, following by capping with dibromo-p-xylene 17 gave rise to a series of chiral

• timescale at room temperature (for 22), the other two dynamic processes, namely circumrotation of the tetracationic cyclophane through the cavity of the polyether and a “rocking motion” of the oxygen–oxygen axis of the hydroquinone units, were fast on the NMR timescale at room temperature. In a follow-up

• study, Stoddart and co-workers employed the BINOL-based macrocycle 23 which contains a 1,5-dioxynapthalene (DNP) unit (in contrast to the hydroquinone unit in macrocycles 15/21). Upon reaction with the achiral precursors 16 and 17, this gives rise to the chiral catenane 24, which was produced in

Menadione: a platform and a target to valuable compounds synthesis

• Acácio S. de Souza,
• Ruan Carlos B. Ribeiro,
• Dora C. S. Costa,
• Fernanda P. Pauli,
• David R. Pinho,
• Matheus G. de Moraes,
• Fernando de C. da Silva,
• Luana da S. M. Forezi and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2022, 18, 381–419, doi:10.3762/bjoc.18.43

• , followed by oxidation, thus establishing a redox cycle. The main characteristics of the quinones (Q) redox cycle, comprises the one-electron reduction to generate a semiquinone intermediate (SQ) and the two-electron reduction leading to hydroquinone (HQ), in NAD(P)H oxidase-dependent processes [35][36][37

• ][38]. In the presence of oxygen, the reduced species is oxidized back to the quinone, thus completing the cycle. In case of naphthoquinones such as menadione, the quinone–semiquinone or quinone–hydroquinone interconversion generates reactive oxygen species (ROS), such as superoxide anion (O2

• ][41]. The quinone–hydroquinone and quinone–semiquinone interconversions, with ROS generation, are responsible for the wide range of biological activities of menadione and its derivatives. An excess of ROS in the intracellular environment can cause harmful effects on structures such as nucleic acids

Application of the Meerwein reaction of 1,4-benzoquinone to a metal-free synthesis of benzofuropyridine analogues

• Rashmi Singh,
• Tomas Horsten,
• Rashmi Prakash,
• Swapan Dey and
• Wim Dehaen

Beilstein J. Org. Chem. 2021, 17, 977–982, doi:10.3762/bjoc.17.79

• to hydroquinone 12 with N,N-diethylhydroxylamine (N,N-DEHA) and cyclized via intramolecular nucleophilic aromatic substitution to isolate 6-hydroxybenzofuro[2,3-b]pyridine (13) with 82% yield. Conveniently, the synthesis of 13 was achieved in a one-pot reaction from 11 with no significant differences

A new and efficient methodology for olefin epoxidation catalyzed by supported cobalt nanoparticles

• Lucía Rossi-Fernández,
• Viviana Dorn and
• Gabriel Radivoy

Beilstein J. Org. Chem. 2021, 17, 519–526, doi:10.3762/bjoc.17.46

• previously made by other authors [15][16][17][41][42][43][44], we assumed that a radical oxidation process could be taking place. To test this assumption, the epoxidation of styrene was carried out under the optimized conditions by adding hydroquinone (5 mg, 0.045 mmol) as radical scavenger. After 8 h of

Synthesis and optoelectronic properties of benzoquinone-based donor–acceptor compounds

• Daniel R. Sutherland,
• Nidhi Sharma,
• Georgina M. Rosair,
• Ifor D. W. Samuel,
• Ai-Lan Lee and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2019, 15, 2914–2921, doi:10.3762/bjoc.15.285

• comparison with the literature data [32][33], the first reduction wave was assigned to the formation of the hydroquinone anion at Ered1 from −0.47 V for 4 to −0.59 V for 2, while the second reduction wave, observed at Ered2 from −1.00 V for 3 to −1.18 V for 2, was assigned to the formation of the

• hydroquinone dianion. LUMO energies of the four compounds are thus in the order of −4.20 eV for compounds 2 and 5 and −4.30 eV for compounds 3 and 4 (Table 1). At positive potentials, the two diphenylamine derivatives (2 and 5) showed reversible one-electron oxidation waves, while the two carbazole donor

Photoreversible stretching of a BAPTA chelator marshalling Ca²⁺-binding in aqueous media

• Aurélien Ducrot,
• Arnaud Tron,
• Robin Bofinger,
• Ingrid Sanz Beguer,
• Jean-Luc Pozzo and
• Nathan D. McClenaghan

Beilstein J. Org. Chem. 2019, 15, 2801–2811, doi:10.3762/bjoc.15.273

• in Scheme 1 and detailed synthetic procedures are given below. Briefly, the synthesis of 1 started with the preparation of a BAPTA core via a multistep route adapting the synthetic route developed by Crossley et al. [35]. 1,4-Hydroquinone was benzylated and subsequently nitrated. This intermediate

Synthesis, enantioseparation and photophysical properties of planar-chiral pillar[5]arene derivatives bearing fluorophore fragments

• Guojuan Li,
• Chunying Fan,
• Guo Cheng,
• Wanhua Wu and
• Cheng Yang

Beilstein J. Org. Chem. 2019, 15, 1601–1611, doi:10.3762/bjoc.15.164

• hydroquinone derivative 7 and 5.0 equiv of paraformaldehyde in the presence of BF3·OEt2 [40][41]. The product was purified by silica gel column chromatography with hexane/ethyl acetate 10:1 as the eluent. The first fraction was permethylated pillar[5]arene, and P5A was collected as the second fraction in 45

Heck- and Suzuki-coupling approaches to novel hydroquinone inhibitors of calcium ATPase

• Robert J. Kempton,
• Taylor A. Kidd-Kautz,
• Soizic Laurenceau and
• Stefan Paula

Beilstein J. Org. Chem. 2019, 15, 971–975, doi:10.3762/bjoc.15.94

• with CAN to the corresponding quinones 11 and 13, respectively. Numerous unsuccessful attempts were made to convert the dimethoxy compound [12] or one of its precursors into a hydroquinone (e.g., 14), either in one step (BBr3·S(CH3)2 [18] or (CH3)3SiCl/NaI [19]), or sequentially (CAN followed by

• cytosolic calcium levels and on the viability of both cancer and healthy cells. Thapsigargin- and hydroquinone-based SERCA inhibitors. Friedel–Crafts alkylation of 4. Heck cross-coupling reactions. Suzuki approach to a tethered hydroquinone. Supporting Information Supporting Information File 369

Synthesis of the aglycon of scorzodihydrostilbenes B and D

• Katja Weimann and
• Manfred Braun

Beilstein J. Org. Chem. 2019, 15, 610–616, doi:10.3762/bjoc.15.56

• , partial hydrogenation of the aromatic rings had to be suppressed. Nevertheless, the aglycon 9 of scorzodihydrostilbenes B and D (2 and 4) was obtained in good yield from 8a. Hydrogenolysis of ketone 8b led to hydroquinone 10, however, along with a minor amount of mono-deprotected phenol 11. The main

• product 10 was isolated in pure form by column chromatography, whereas the fraction containing the phenol 11 was still contaminated with hydroquinone 10 (Scheme 3). Finally, the glycosylation of the aglycon 9 was briefly studied using Helferich’s method [19]. It turned out that, upon treatment of 9 with β

• the column chromatography contained mono-deprotected 1-[3-(benzyloxy)-6-hydroxy-2-(4-methoxyphenethyl)phenyl]ethan-1-one (11) that was still contaminated with a small amount of hydroquinone 10. Yield: 68 mg (16%); Rf 0.3; 1H NMR (CDCl3, 600 MHz) δ 2.65 (s, 3H), 2.82–2.85 (m, 2H), 3.04–3.09 (m, 2H

Calixazulenes: azulene-based calixarene analogues – an overview and recent supramolecular complexation studies

• Paris E. Georghiou,
• Shofiur Rahman,
• Abdullah Alodhayb,
• Hidetaka Nishimura,
• Jaehyun Lee,
• Atsushi Wakamiya and
• Lawrence T. Scott

Beilstein J. Org. Chem. 2018, 14, 2488–2494, doi:10.3762/bjoc.14.225

• reported in the literature [7]. Besides the classical calixarene phenolic subunits linked by methylene groups, “calixarenes” incorporating other subunits include, but are not limited to, resorcinol [8], hydroquinone [9], naphthols [10], pyrrole [11], heteroaromatics [12] and triptycene [13] in their cavity

An amphiphilic pseudo[1]catenane: neutral guest-induced clouding point change

• Tomoki Ogoshi,
• Tomohiro Akutsu and
• Tada-aki Yamagishi

Beilstein J. Org. Chem. 2018, 14, 1937–1943, doi:10.3762/bjoc.14.167

• % [23]. Pillar[5]arene carrying 2 alkyne groups on the same unit (5). In a similar manner as described in [24], 5 was prepared. Under a nitrogen atmosphere, pillar[5]arene carrying one hydroquinone unit 6 [7] (Scheme 1, 417 mg, 0.230 mmol) was dissolved in acetone (10 mL). K2CO3 (159 mg, 1.15 mmol) was

Preparation of trinucleotide phosphoramidites as synthons for the synthesis of gene libraries

• Ruth Suchsland,
• Bettina Appel and
• Sabine Müller

Beilstein J. Org. Chem. 2018, 14, 397–406, doi:10.3762/bjoc.14.28

• , the disulfide tether was replaced in a following-up study with a Q-linker (hydroquinone-O,O'-diacetic acid), to be cleaved with dilute methanolic K2CO3 for the release of trimers in fully protected form. Five different trimers were assembled at 0.5 mmol scale and released form the support as described

CF₃SO₂X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation. Part 1: Use of CF₃SO₂Na

• Hélène Guyon,
• Hélène Chachignon and
• Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2764–2799, doi:10.3762/bjoc.13.272

• conditions tolerated a broad range of functional groups and the yields ranged from 31 to 68% (Scheme 50). During the process, the quinone was converted into hydroquinone and a regeneration process was established by passing through a cartridge of MnO2. A mechanism for this transformation was proposed as a

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

• of 90% (Scheme 60) [63]. Similarly, 6-hydroxy- and 7-hydroxycoumarin derivatives were obtained from hydroquinone and resorcinol, respectively (Scheme 60) [75]. The same kind of reaction with the participation of 2,4-dihydroxybenzaldehyde or 2,4-dihydroxy-3-methylbenzaldehyde was applied in 2010 by

Palladium-catalyzed Heck-type reaction of secondary trifluoromethylated alkyl bromides

• Tao Fan,
• Wei-Dong Meng and
• Xingang Zhang

Beilstein J. Org. Chem. 2017, 13, 2610–2616, doi:10.3762/bjoc.13.258

• %), Xantphos (7.5 mol %) and KOAc in DCE at 80 °C, the addition of an electron transfer scavenger 1,4-dinitrobenzene [25][26][27] dramatically diminished the yield of 3a (Table 2, entries 2 and 3), and catalytic amount of radical inhibitor hydroquinone totally shut down the reaction (Table 2, entry 4). Thus