Synthesis of acenaphthylene-fused heteroarenes and polyoxygenated benzo[j]fluoranthenes via a Pd-catalyzed Suzuki–Miyaura/C–H arylation cascade

• Merve Yence,
• Dilgam Ahmadli,
• Damla Surmeli,
• Umut Mert Karacaoğlu,
• Sujit Pal and
• Yunus Emre Türkmen

Beilstein J. Org. Chem. 2024, 20, 3290–3298, doi:10.3762/bjoc.20.273

• ] or catechol [47] boronic esters as the final products. Therefore, it is important that they can be directly utilized with our methodology without further boronic ester interconversions. To this end, we first tested the reaction of thiophene-3-ylboronic acid pinacol ester (17b), and we were pleased to

• see that the desired product 15a was isolated with a similar reaction yield (78%, Table 1, entry 2). Thiophene-3-ylboronic acid catechol ester (17c) was also found to be a competent reaction partner affording the final product 15a successfully, albeit in a slightly lower yield (69%, Table 1, entry 3

Synthesis, electrochemical properties, and antioxidant activity of sterically hindered catechols with 1,3,4-oxadiazole, 1,2,4-triazole, thiazole or pyridine fragments

• Daria A. Burmistrova,
• Andrey Galustyan,
• Nadezhda P. Pomortseva,
• Kristina D. Pashaeva,
• Maxim V. Arsenyev,
• Oleg P. Demidov,
• Mikhail A. Kiskin,
• Andrey I. Poddel’sky,
• Nadezhda T. Berberova and
• Ivan V. Smolyaninov

Beilstein J. Org. Chem. 2024, 20, 2378–2391, doi:10.3762/bjoc.20.202

• established for these compounds. The electrochemical behavior of the studied compounds is influenced by several factors: the nature of the heterocycle and its substituents, the presence of a sulfur atom in the catechol ring, or a thione group in the heterocyclic core. The radical scavenging activity and

• : antioxidant activity; catechol thioethers; heterocycles; redox-transformations; thiones; Introduction Synthetic derivatives of polyphenols, in particular catechol (hydroquinone), represent a promising group of pharmacologically active substances [1][2]. Catechol-containing compounds demonstrate

• derivatives are used as ligands in the synthesis of metal complexes (Ni(II), Pd(II), Pt(II), Cu(I), Ag(I) etc.) exhibiting antibacterial and antitumor activity [34]. In most cases, polyfunctional catechol thioethers were obtained by Michael reaction via the interaction of o-, p-benzoquinone and the

Natural resorcylic lactones derived from alternariol

• Joachim Podlech

Beilstein J. Org. Chem. 2024, 20, 2171–2207, doi:10.3762/bjoc.20.187

Competing electrophilic substitution and oxidative polymerization of arylamines with selenium dioxide

• Vishnu Selladurai and
• Selvakumar Karuthapandi

Beilstein J. Org. Chem. 2024, 20, 1221–1235, doi:10.3762/bjoc.20.105

• of quinones having exceptional radical-stabilizing abilities. The best example in nature is the radical pathway in the catechol oxidation process [56][57][58]. The structure of o-anisidine resembles catechol as it has two adjacent electron-donating functions (NH2 and OMe). For o-anisidine, the amine

(Bio)isosteres of ortho- and meta-substituted benzenes

• H. Erik Diepers and
• Johannes C. L. Walker

Beilstein J. Org. Chem. 2024, 20, 859–890, doi:10.3762/bjoc.20.78

Tying a knot between crown ethers and porphyrins

• Maksym Matviyishyn and
• Bartosz Szyszko

Beilstein J. Org. Chem. 2023, 19, 1630–1650, doi:10.3762/bjoc.19.120

• ether systems, where the catechol unit of the crown ether was fused to two β-pyrrolic positions of the porphyrin periphery. The systems presented intriguing intramolecular electron-transfer properties. Additionally, they were investigated as fluorescent sensors for various organic and metal cations [51

Radical chemistry in polymer science: an overview and recent advances

• Zixiao Wang,
• Feichen Cui,
• Yang Sui and
• Jiajun Yan

Beilstein J. Org. Chem. 2023, 19, 1580–1603, doi:10.3762/bjoc.19.116

• based on the radical polymerization of catechol derivatives. Catechols are known as easily oxidizable compounds and are prone to undergo oxidation by losing one or two electrons [3]. This way, either semiquinone radicals or o-quinones are formed by single or double-electron oxidation, respectively [4

• ]. The semiquinone radicals formed during the oxidation of catechol can undergo a cross-coupling reaction to form polymers (Scheme 1). One example is the radical polymerization of urushiol. The earliest recorded application of natural radical polymerization can be traced back to the manufacture of

• and in-depth dialogs between the organic and polymer communities. Therefore, future opportunities for polymer science evolution lie in the collaboration of radical chemists in both communities. Used abbreviations in the text and their explanations are collected in Table 2. Oxidation of catechol and

Synthesis of 5-arylidenerhodanines in L-proline-based deep eutectic solvent

• Stéphanie Hesse

Beilstein J. Org. Chem. 2023, 19, 1537–1544, doi:10.3762/bjoc.19.110

• . Moreover, it has already been shown that a catechol-like structure greatly contributes to the antioxidant activity in DPPH scavenging activities [43]. The antioxidant activities of compounds 3a–h are presented in Table 4 and our results were consistent with the observations of Molnar et al. [3], i.e., 3,4

• hydroxy group showed DPPH radical scavenging activity. Compound 3d with a catechol-like structure exhibited the best antioxidant activity. Experimental General procedure for the Knoevenagel condensation DES (0.8 g) was introduced in a 10 mL round-bottomed flask. Then, the aldehyde (0.5 mmol) and rhodanine

Group 13 exchange and transborylation in catalysis

• Dominic R. Willcox and
• Stephen P. Thomas

Beilstein J. Org. Chem. 2023, 19, 325–348, doi:10.3762/bjoc.19.28

• ) [111]. The reaction was proposed to proceed through the enantioselective reduction of the ketone 95 by gallium hydride 96, followed by Ga‒O/B‒H exchange with HBcat to give an enantioenriched alkoxy catechol borane 98, affording the alcohol after workup (Scheme 24a). The mechanism was later explored in

Trichloroacetic acid fueled practical amine purifications

• Aleena Thomas,
• Baptiste Gasch,
• Enzo Olivieri and
• Adrien Quintard

Beilstein J. Org. Chem. 2022, 18, 225–231, doi:10.3762/bjoc.18.26

• isolated in its pure form starting from model mixtures containing various aromatics, phenols, alkanes or alkenes in overall purification yields ranging from 53 to 98%. The lower yields are observed for coordinating phenol and catechol (Table 2, entries 3 and 4), probably impacting the crystallization

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

¹⁹F NMR as a tool in chemical biology

• Diana Gimenez,
• Aoife Phelan,
• Cormac D. Murphy and
• Steven L. Cobb

Beilstein J. Org. Chem. 2021, 17, 293–318, doi:10.3762/bjoc.17.28

• , but only one could be detected (SF5-catechol) despite the 19F NMR analysis showing the presence of multiple fluorometabolites. Detection and biosynthesis of natural organofluorine compounds As naturally-occurring organofluorine compounds are so rare, it is possible to easily detect them in a crude

Annulation of a 1,3-dithiole ring to a sterically hindered o-quinone core. Novel ditopic redox-active ligands

• Sergey V. Norkov,
• Anton V. Cherkasov,
• Andrey S. Shavyrin,
• Maxim V. Arsenyev,
• Viacheslav A. Kuropatov and
• Vladimir K. Cherkasov

Beilstein J. Org. Chem. 2021, 17, 273–282, doi:10.3762/bjoc.17.26

• coordination ability. The redox state of o-quinone (semiquinone or catechol) could be changed both as free species or when it is coordinated to a metal ion as a ligand. Thus, the redox isomerism phenomenon was reported for o-quinone complexes with both transition and non-transition metals [1][2][3]. The

• reduction with sodium dithionite in a water/methanol mixture: at these conditions o-quinone 6a converts into catechol 10. It has been shown also that the thiocarbonyl group in 6a could be easily converted into a carbonyl group by action of mercury(II) acetate in solution (Scheme 3). EPR spectroscopy studies

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

• between the catechol ring of the crown ether and aromatic moieties of the secondary ammonium ion contribute to the complex formation [22][23][24][25]. Over the last 25 years, a detailed understanding of the thermodynamic and kinetic properties of crown ether/ammonium complexes has developed enabling the

Hierarchically assembled helicates as reaction platform – from stoichiometric Diels–Alder reactions to enamine catalysis

• David Van Craen,
• Jenny Begall,
• Johannes Großkurth,
• Leonard Himmel,
• Oliver Linnenberg,
• Elisabeth Isaak and
• Markus Albrecht

Beilstein J. Org. Chem. 2020, 16, 2338–2345, doi:10.3762/bjoc.16.195

• ]. Catechol ligands L-H2 with an ester functionality in the 3-position were prepared via conversion of the acid chloride of 2,3-dihydroxybenzoic acid to the corresponding esters. These ligands underwent a complexation with titanoyl(IV) bisacetylacetonate and lithium carbonate initially forming a mononuclear

• ][17][18][19][20]. Enantioselectivities up to 25% ee at elevated temperature (32% ee at 0 °C) depending on the substrate were achieved in a Diels–Alder reaction by introducing two different substituted catechol ester ligands during the complex formation: (1) A diene-substituted ligand 1-H2 for the

• the amino alcohols 10a–d were protected with a Boc group [42][43]. Esterification of the protected alcohols 11a–d [33][44] with 2,3-dioxosulfinylbenzoyl chloride obtained from 2,3-dihydroxybenzoic acid and thionyl chloride afforded the N-Boc-substituted catechol ligands 12a–d [33][36]. They were

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

• ]. A strongly fluorescent compound, 3, has been isolated from the reaction of ethylenediamine with noradrenaline, 2-methylnoradrenaline, adrenolone, 3,4-dihydroxymandelic acid or catechol [8]. The reaction with 2,5-dihydroxy-p-benzoquinone (4) under a stream of air affording 3 in 50% yield was proposed

Borylation and rearrangement of alkynyloxiranes: a stereospecific route to substituted α-enynes

• Ruben Pomar Fuentespina,
• José Angel Garcia de la Cruz,
• Gabriel Durin,
• Victor Mamane,
• Jean-Marc Weibel and
• Patrick Pale

Beilstein J. Org. Chem. 2019, 15, 1416–1424, doi:10.3762/bjoc.15.141

• (see below) to be trapped by various phenylboronic esters 2. The resulting borate intermediate afforded the tetrasubstituted enyne 3 in good to moderate yields, depending on the boronic ester’s nature (Table 1). The catechol ester 2a only provided a modest yield of 3 (Table 1, entry 1), while the

The design and synthesis of an antibacterial phenothiazine–siderophore conjugate

• Abed Tarapdar,
• James K. S. Norris,
• Oliver Sampson,
• Galina Mukamolova and
• James T. Hodgkinson

Beilstein J. Org. Chem. 2018, 14, 2646–2650, doi:10.3762/bjoc.14.242

• functionalised phenothiazine demonstrated an equipotent MIC value in direct comparison to the parent phenothiazine from which it was derived. The final conjugate was synthesised by amide bond formation between the two components and global deprotection of the PMB protecting groups to unmask the catechol iron

• antituberculosis activity. We were pleased to observe side by side compound 4 exhibited equimolar MIC values to 1 (6.25 μM, 1 and 4) against M. smegmatis. Next our attention turned to the siderophore component of the conjugate. In our proof of concept study we chose to synthesise the bis-catechol siderophore

• azotochelin. Catechol-based siderophores can act as xenosiderophores and be recognised for uptake by Gram-negative bacteria and mycobacteria [14][15]. Most commonly benzyl protecting groups are used in the synthesis of catechol siderophores and cleaved in the final step by palladium catalysed hydrogenation

Targeting the Pseudomonas quinolone signal quorum sensing system for the discovery of novel anti-infective pathoblockers

• Christian Schütz and
• Martin Empting

Beilstein J. Org. Chem. 2018, 14, 2627–2645, doi:10.3762/bjoc.14.241

• attachment of a cell-penetrating peptide sequence [58]. One additional class, which did show cellular activity, was based on a catechol scaffold [59]. In analogy to the successful discovery of PqsD inhibitors starting from known FabH-targeting compounds (vide supra), ligands of another enzyme with high

Chiral bisoxazoline ligands designed to stabilize bimetallic complexes

• Deepankar Das,
• Rudrajit Mal,
• Nisha Mittal,
• Zhengbo Zhu,
• Thomas J. Emge and
• Daniel Seidel

Beilstein J. Org. Chem. 2018, 14, 2002–2011, doi:10.3762/bjoc.14.175

• monooxygenase [10], ribonucleotide reductase [11], catechol oxidase [12], and arginase [13], are prominent examples of such bimetallic enzymes. A range of bi- and multi-metallic complexes have been utilized in asymmetric catalysis (Figure 1) [6]. For instance, Shibasaki and co-workers introduced a number of

Synthesis of spirocyclic scaffolds using hypervalent iodine reagents

• Fateh V. Singh,
• Priyanka B. Kole,
• Saeesh R. Mangaonkar and
• Samata E. Shetgaonkar

Beilstein J. Org. Chem. 2018, 14, 1778–1805, doi:10.3762/bjoc.14.152

• starting from catechol derivative 142. Marine sesquiterpenoids are mainly known for their biological importance such as antitumor, antiviral and antibiotic properties [132]. In this report, the catechol-derived starting substrate 142 was cyclized to spirocyclic product 143 in 67% yield using PIFA (31) as

• ) as an electrophile. Oxidative spirocyclization of phenolic compound 139 to spirodienone 140 using polymer-supported PIDA 132. PIFA-mediated oxidative cyclization of catechol derived substrate 142 to spirocyclic product 143. Oxidative spirocyclization of p-substituted phenolic substrate 145 to

Anomeric modification of carbohydrates using the Mitsunobu reaction

• Julia Hain,
• Patrick Rollin,
• Werner Klaffke and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2018, 14, 1619–1636, doi:10.3762/bjoc.14.138

• stereoselectively from the 2-deoxy-carbasugar 73 in a Mitsunobu reaction with the aglycon 74 [55]. Benzyl protection, which does not exert neighboring group effects in classical glycosylations, resulted in the predominant formation of 1,2-trans glycosides in the Mitsunobu reaction with catechol. In fact, benzyl

• . Stereoselectivity in the Mitsunobu synthesis of catechol glycosides in the gluco- and manno-series [56]. Formation of a 1,2-cis glycoside 80 assisted by steric hindrance of the β-face of the disaccharide through the DTBS protection. DTBS: di-tert-butylsilylene; Troc: 2,2,2-trichloroethoxycarbonyl [22

Synthesis of naturally-derived macromolecules through simplified electrochemically mediated ATRP

• Paweł Chmielarz,
• Tomasz Pacześniak,
• Katarzyna Rydel-Ciszek,
• Izabela Zaborniak,
• Paulina Biedka and
• Andrzej Sobkowiak

Beilstein J. Org. Chem. 2017, 13, 2466–2472, doi:10.3762/bjoc.13.243

• , both for water-containing [28][59] and for aprotic media [28][60][61] the first oxidation peak corresponds to the oxidation of the catechol moiety, the 3’,4’-dihydroxy group of quercetin, while the second peak relates to the oxidation of the –OH substituent next to the carbonyl group of quercetin

Synthesis and application of trifluoroethoxy-substituted phthalocyanines and subphthalocyanines

• Satoru Mori and
• Norio Shibata

Beilstein J. Org. Chem. 2017, 13, 2273–2296, doi:10.3762/bjoc.13.224

• catechol, resorcinol or hydroquinone in toluene in the presence of triethylamine (Scheme 11) [131]. The synthesis of H-subPc homodimer 30 was attempted using the same method, but the target substance was obtained. This is a good example showing the high activity of the axial substitution reaction of TFEO

Solid-state studies and antioxidant properties of the γ-cyclodextrin·fisetin inclusion compound

• Joana M. Pais,
• Maria João Barroca,
• Maria Paula M. Marques,
• Filipe A. Almeida Paz and
• Susana S. Braga

Beilstein J. Org. Chem. 2017, 13, 2138–2145, doi:10.3762/bjoc.13.212

• of significant blueshifts in bands associated with the catechol ring (B) is indicative of its deep penetration into the γ-CD cavity, thus confirming the formation of a true inclusion compound in the product. The band observed at 1445 cm−1 in pure fisetin, associated with stretching of the A and C