Methodology for awakening the potential secondary metabolic capacity in actinomycetes

• Shun Saito and
• Midori A. Arai

Beilstein J. Org. Chem. 2024, 20, 753–766, doi:10.3762/bjoc.20.69

• , ytterbium (Yb), but not in the presence of other metals. Structural analyses revealed that this pigment is a type of naphthoquinone similar to nanaomycin (24) [64]. Furthermore, Tanaka et al. showed that low concentrations of the rare earth elements scandium (Sc) and/or lanthanum (La) markedly activate (2.5

Copper-catalyzed N-arylation of amines with aryliodonium ylides in water

• Kasturi U. Nabar,
• Bhalchandra M. Bhanage and
• Sudam G. Dawande

Beilstein J. Org. Chem. 2023, 19, 1008–1014, doi:10.3762/bjoc.19.76

• -arylation of amines using iodonium ylides obtained from 2-hydroxy-1,4-naphthoquinone in the presence of a Cu(II) catalyst in dichloromethane as a solvent (Scheme 1b) [41]. Albeit useful, this protocol suffers drawbacks such as low yields, formation of byproducts, limited substrate study, and the use of

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

• biomimetic oxidation of benzyl alcohols was developed using o-naphthoquinone [129] (Scheme 28). The reaction shows regioselectivity toward benzylic alcohol oxidation. This process could be included in one-pot synthesis strategies. The key step of the reaction is a 1,5-hydrogen transfer (the suggested

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

• , Brazil 10.3762/bjoc.18.43 Abstract Naphthoquinones are important natural or synthetic compounds belonging to the general class of quinones. Many compounds in this class have become drugs that are on the pharmaceutical market for the treatment of various diseases. A special naphthoquinone derivative is

• menadione, a synthetic naphthoquinone belonging to the vitamin K group. This compound can be synthesized by different methods and it has a broad range of biological and synthetic applications, which will be highlighted in this review. Keywords: cancer; chemical reactions; 2-methyl-1,4-naphthoquinone

• interesting chemical properties and bioactivities, naphthoquinones have aroused great interest, mainly in the pharmaceutical field, where they have been widely used in the development of new and more efficient drugs [1][9]. The naphthoquinone menadione has attracted a lot of attention. Menadione or 2-methyl

1,2-Naphthoquinone-4-sulfonic acid salts in organic synthesis

• Ruan Carlos B. Ribeiro,
• Patricia G. Ferreira,
• Amanda de A. Borges,
• Luana da S. M. Forezi,
• Fernando de Carvalho da Silva and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2022, 18, 53–69, doi:10.3762/bjoc.18.5

• against various microorganisms and pharmacological targets, including being used in the preparation of several drugs that are on the pharmaceutical market. Among these naphthoquinones, the series of compounds prepared from 1,2-naphthoquinone-4-sulfonic acid salts (β-NQS) stands out. In addition to being

• catecholamines and other compounds, but they can also be ingested as exogenous products of air and water. The most common quinones, such as benzoquinone, naphthoquinone, anthraquinone, and phenanthrenequinone, can be formed by incomplete combustion or photooxidation of their respective polycyclic aromatic

• electrons through a redox cycle promoted by the 1,2- or 1,4-naphthoquinone system. In this cycle, transient reactive oxygen (ROS) and nitrogen (RNS) species are formed as free radicals, peroxides, superoxide anions, radical anions, or dianions. These species generated inside cells accelerate hypoxia and

Recent advances in the syntheses of anthracene derivatives

• Giovanni S. Baviera and
• Paulo M. Donate

Beilstein J. Org. Chem. 2021, 17, 2028–2050, doi:10.3762/bjoc.17.131

• -workers [77] provided better results. In a related approach, Estévez-Braun and co-workers synthesized dibenzo[a,h]anthracene-12,13-diones 188 from 2-hydroxy-1,4-naphthoquinone (186), β-naphthol (181), and aromatic aldehydes 187 through a multicomponent reaction that used InCl3 as catalyst under solvent

• multicomponent reactions employing 2-hydroxy-1,4-naphthoquinone (186), β-naphthol (181), and aromatic aldehydes. Synthesis of substituted anthraquinones catalyzed by an AlCl3/MeSO3H system. Palladium(II)-catalyzed/visible light-mediated synthesis of anthraquinones. [4 + 2] Anionic annulation reaction for the

A straightforward conversion of 1,4-quinones into polycyclic pyrazoles via [3 + 2]-cycloaddition with fluorinated nitrile imines

• Greta Utecht-Jarzyńska,
• Karolina Nagła,
• Grzegorz Mlostoń,
• Heinz Heimgartner,
• Marcin Palusiak and
• Marcin Jasiński

Beilstein J. Org. Chem. 2021, 17, 1509–1517, doi:10.3762/bjoc.17.108

• naphthoquinone-derived products and low-intensity bands in the visible region (≈400 nm) for the anthraquinone series. Keywords: [3 + 2]-cycloadditions; fluorinated compounds; fused pyrazoles; N-heterocycles; nitrile imines; 1,4-quinones; Introduction The 1,4-quinone scaffold belongs to the most important

• exclusively [16]. Noteworthy, [3 + 2]-cycloadditions of nitrile imines to the C=O group of 1,4-quinones have not yet been reported. In a historical work by Rolf Huisgen et al., the first [3 + 2]-cycloadditions of some 1,4-quinones, e.g., 1,4-naphthoquinone (1a), with C,N-diphenyl nitrile imine (2) were

• 1,4-naphthoquinone (1a) and 1,4-anthraquinone (1b), which were selected as model dipolarophiles. In addition, an important issue of the work was the examination of the chemoselectivity governing the formation of five-membered rings via competitive cycloaddition of the in-situ-generated 1,3-dipoles

Microwave-assisted multicomponent reactions in heterocyclic chemistry and mechanistic aspects

• Shivani Gulati,
• Stephy Elza John and
• Nagula Shankaraiah

Beilstein J. Org. Chem. 2021, 17, 819–865, doi:10.3762/bjoc.17.71

• exploring the MC-MWA reactions Jiang and co-workers [41] designed a microwave facilitated regioselective four-component domino reaction employing naphthyl- or anthracenylamine 10, aldehydes 5 and 2-hydroxy-1,4-naphthoquinone (11) in acetic acid for the construction of dibenzo[a,h]acridine-12,13(7H,14H

Recent developments in enantioselective photocatalysis

• Callum Prentice,
• James Morrisson,
• Andrew D. Smith and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2020, 16, 2363–2441, doi:10.3762/bjoc.16.197

• naphthoquinones 216 to afford enantioenriched benzofuranones 217 (Scheme 33) [93]. They then expanded the scope of the naphthoquinone by coupling this reaction with a photocatalysed oxidation of naphthols 218 to generate 216 in situ. While no detailed mechanism has been proposed, based on prior work of Hawkins et

The biomimetic synthesis of balsaminone A and ellagic acid via oxidative dimerization

• Sharna-kay Daley and
• Nadale Downer-Riley

Beilstein J. Org. Chem. 2020, 16, 2026–2031, doi:10.3762/bjoc.16.169

• ), was subjected to the oxidants activated carbon (Act-C), potassium ferricyanide (K3[Fe(CN)6]), p-benzoquinone and stannic chloride (SnCl4). As shown in Scheme 4, with the exception of SnCl4, all oxidants resulted in the re-oxidation of the hydroxylated substrate to naphthoquinone 7. SnCl4, however

Combining enyne metathesis with long-established organic transformations: a powerful strategy for the sustainable synthesis of bioactive molecules

• Valerian Dragutan,
• Ileana Dragutan,
• Albert Demonceau and
• Lionel Delaude

Beilstein J. Org. Chem. 2020, 16, 738–755, doi:10.3762/bjoc.16.68

• method, an enyne precursor was first converted into an exocyclic 1,3-diene in 92% yield. A Diels–Alder reaction with naphthoquinone and a deprotection step then led to the final compound (−)-zenkequinone B in a stereoselective manner (Scheme 23). C-Aryl glycosides Another interesting report from

First thia-Diels–Alder reactions of thiochalcones with 1,4-quinones

• Grzegorz Mlostoń,
• Katarzyna Urbaniak,
• Paweł Urbaniak,
• Anna Marko,
• Anthony Linden and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2018, 14, 1834–1839, doi:10.3762/bjoc.14.156

• 1,4-benzoquinone, 1,4-naphthoquinone, and 1,4-anthraquinone were investigated as a route to novel 4H-thiochromene-5,8-dione derivatives. Results and Discussion Aryl and hetary lthiochalcones 1a–d are easily obtained by treatment of the corresponding chalcones with Lawesson′s reagent in THF solution

• [15]. Along with the commercially available 1,4-benzoquinone (2a) and 1,4-naphthoquinone (2b), 1,4-anthraquinone (2c) and 5-chloro-10-hydroxy-1,4-anthraquinone (2d) were prepared from quinizarine according to known procedures [27][28]. First experiments were performed with 2b and thiochalcones 1a–d in

• -Benzoquinone (2a) and 1,4-naphthoquinone (2b) were commercial reagents and used without further purification. 1,4-Anthraquinone (2c) was prepared from commercial quinizarine by treatment with sodium borohydride according to a literature procedure [27]. 5-Chloro-10-hydroxy-1,4-anthraquinone (2d) was obtained by

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

• of palmarumycin CP1 were synthesized later which were showing good thioredoxin–thioredoxin reductase (Trx-1/TrxR) inhibitory activity [129]. It was observed that the introduction of enone functionality in naphthoquinone spiroketal enhances the biological activity of palmarumycin 138. Furthermore, Ley

• pathway for the synthesis of the naturally occurring antibiotic platensimycin (154) which is isolated from Streptomyces platensis. In this report, 6-methoxy-1,4-naphthoquinone-4-ethylene ketal (153) was synthesized by intermolecular oxidative cyclization of 7-methoxy-α-naphthol (152) with ethylene glycol

One hundred years of benzotropone chemistry

• Arif Dastan,
• Haydar Kilic and
• Nurullah Saracoglu

Beilstein J. Org. Chem. 2018, 14, 1120–1180, doi:10.3762/bjoc.14.98

• depicted in Scheme 38 (Scheme 45) [161]. Sato’s group reported the synthesis of 7-hydroxy-2,3-benzotropone (241) via the ring expansion pathway of β-naphthoquinone (280) with diazomethane under various conditions and hydrolysis steps (Scheme 46) [169]. The boron trifluoride etherate-promoted ring expansion

An air-stable bisboron complex: a practical bidentate Lewis acid catalyst

• Longcheng Hong,
• Sebastian Ahles,
• Andreas H. Heindl,
• Gastelle Tiétcha,
• Andrey Petrov,
• Zhenpin Lu,
• Christian Logemann and
• Hermann A. Wegner

Beilstein J. Org. Chem. 2018, 14, 618–625, doi:10.3762/bjoc.14.48

• acid catalyst B (25.0 µmol, 5.00 mol %) and 1,2,4,5-tetrazine (5.00 equiv) in CF3Ph (2.5 mL) were thoroughly stirred for several minutes. Then, 1,4-naphthoquinone (1.00 equiv) was added, the reaction mixture was heated at 110 °C for 20 h. The solvent, together with the excess of 1,2,4,5-tetrazine were

Mannich base-connected syntheses mediated by ortho-quinone methides

• Petra Barta,
• Ferenc Fülöp and
• István Szatmári

Beilstein J. Org. Chem. 2018, 14, 560–575, doi:10.3762/bjoc.14.43

• , mutagenous properties were also shown. Freccero et al. examined the photogeneration by laser flash photolysis and reactivity of naphthoquinone methides as well as their activity as purine selective DNA alkylating agents [93]. Farrell et al. studied the mechanism of the cytotoxic action of naphthoquinone

Design and synthesis of propellane derivatives and oxa-bowls via ring-rearrangement metathesis as a key step

• Sambasivarao Kotha and
• Rama Gunta

Beilstein J. Org. Chem. 2015, 11, 1727–1731, doi:10.3762/bjoc.11.188

• from readily accessible starting materials such as p-benzoquinone, 1,4-naphthoquinone and 1,4-anthraquinone. Keywords: allylation; propellane derivatives; quinones; ring-rearrangement metathesis; Introduction The synthesis of complex target structures requires bond-disconnection analysis of the

• -quinones (p-benzoquinone, 1,4-naphthoquinone or 1,4-anthraquinone) with a freshly cracked cyclopentadiene. To realize the synthetic strategy (Figure 1) to various propellane derivatives [29][30][31] and oxa-bowls, we commenced with the preparation of a known DA adduct 3a [32]. Subsequent allylation of 3a

• compounds 2a and 1a have been confirmed on the basis of 1H, 13C NMR and DEPT-135 spectral data and further supported by HRMS data. To expand the strategy, another DA adduct 3b was prepared from the commercially available 1,4-naphthoquinone and freshly cracked cyclopentadiene by following the literature

Spiro annulation of cage polycycles via Grignard reaction and ring-closing metathesis as key steps

• Sambasivarao Kotha,
• Mohammad Saifuddin,
• Rashid Ali and
• Gaddamedi Sreevani

Beilstein J. Org. Chem. 2015, 11, 1367–1372, doi:10.3762/bjoc.11.147

• -pyrano cage compound 7 involving ring-closing metathesis is reported. The hexacyclic dione 10 was prepared from simple and readily available starting materials such as 1,4-naphthoquinone and cyclopentadiene. The synthesis of an unprecedented octacyclic cage compound through intramolecular Diels–Alder (DA

• 10 could be constructed in two steps from readily available starting materials such as 1,4-naphthoquinone (9) and cyclopentadiene (8) [40][41]. Results and Discussion In connection with the synthesis of new cage molecules, we reported a new approach to the hexacyclic dione 10 and related systems via

A new and efficient procedure for the synthesis of hexahydropyrimidine-fused 1,4-naphthoquinones

• Marcelo Isidoro P. Reis,
• Vinícius R. Campos,
• Jackson A. L. C. Resende,
• Fernando C. Silva and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2015, 11, 1235–1240, doi:10.3762/bjoc.11.137

• ]quinazoline; microwave; naphthoquinone; 1,3-quinazoline; 1,3,5-triazinane; Introduction Quinones represent a diverse family of naturally occurring secondary metabolites [1][2][3]. Interest in these substances has intensified in recent years due to their pharmacological importance [4]. Heterocycle-fused

• demonstrated to display various biological activities. There are several specific and general methods reported in the literature that describe the preparation and biological activity of heterocycle-fused naphthoquinone compounds [35]. Recently, Iida et al. described a general method for the construction of

• unsymmetrical hexahydropyrimidine-fused 1,2- and 1,4-naphthoquinones by the reaction of 4-amino-l,2-naphthoquinone and 2-amino-1,4-naphthoquinone with amines and formaldehyde in moderate yields [37]. Ohta et al. studied the nucleophilic addition reaction of methylamine to 2-bromo-3-hydroxymethyl-1,4

Glycoluril–tetrathiafulvalene molecular clips: on the influence of electronic and spatial properties for binding neutral accepting guests

• Yoann Cotelle,
• Marie Hardouin-Lerouge,
• Stéphanie Legoupy,
• Olivier Alévêque,
• Eric Levillain and
• Piétrick Hudhomme

Beilstein J. Org. Chem. 2015, 11, 1023–1036, doi:10.3762/bjoc.11.115

• molecular clip 2 in 48% yield using similar experimental conditions. Whereas the synthesis of molecular clips 1, 2 and 3 uses the nucleophilic substitution onto diphenylglycoluril 5 as a key-step, the introduction of the naphthoquinone spacer in clip 4 required the previous transformation of compound 5 into

• -empirical AM1 method in the case of 4 [19]. This distance was estimated to be equal to 9.7 Å indicating that this enlargement around 2 Å was the result mainly of the spatial contribution of the additional naphthoquinone spacer in molecular clip 4. Electrochemical properties The electrochemical behaviour of

• intermolecular electronic interactions between them. It should be noted that the electroactive naphthoquinone acceptor group incorporated in the spacer unit is characterized by a reduction wave (Eapp0red1) at −1.05 V vs Fc+/Fc. On the contrary, the CV of clips 1–3 shows a significant splitting of the first

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

• de Química, Universidad Técnica Federico Santa María, Casilla 110-V, Valparaíso, Chile Departamento de Química, Facultad de Ciencias Básicas Universidad de Antofagasta, Casilla 170, Antofagasta, Chile 10.3762/bjoc.10.255 Abstract A number of N-phenyl-1,4-naphthoquinone monoimines 6–10 were prepared

• conventional oxidative phenylamination procedures, this novel synthetic method offers the advantage of aerobic conditions “on water” instead of hazardous oxidant reagents currently employed in aqueous alcoholic media. Keywords: 1,4-naphthoquinone monoimines; on water; oxidative coupling; rose bengal; solar

• [1][2][3][4][5][6]. In this context, the sunlight-induced synthesis of 5-hydroxy-1,4-naphthoquinone (2, juglone, Figure 1) by sensitized phothooxygenation of 1,5-dihydroxynaphthalene (1, 1,5-DHN) [7] and the preparation of 2-phenylamino-1,4-naphthoquinones by reaction of 1,4-naphthoquinones with

Boron-substituted 1,3-dienes and heterodienes as key elements in multicomponent processes

• Ludovic Eberlin,
• Fabien Tripoteau,
• François Carreaux,
• Andrew Whiting and
• Bertrand Carboni

Beilstein J. Org. Chem. 2014, 10, 237–250, doi:10.3762/bjoc.10.19

• presence of Yb(fod)3 to afford 2-alkoxy-3,4-dihydro-5-vinyl-2H-pyran 33. In the presence of electron-poor dienophiles, as N-phenylmaleimide, maleic anhydride, activated azo compounds or naphthoquinone, 33 underwent normal Diels–Alder reactions thus giving the corresponding cycloadducts 34 as single

New hydrogen-bonding organocatalysts: Chiral cyclophosphazanes and phosphorus amides as catalysts for asymmetric Michael additions

• Helge Klare,
• Jörg M. Neudörfl and
• Bernd Goldfuss

Beilstein J. Org. Chem. 2014, 10, 224–236, doi:10.3762/bjoc.10.18

• to 2-hydroxy-1,4-naphthoquinone With these novel catalysts in hands we tested their efficiency in enantioselective catalysis. The reaction of 2-hydroxy-1,4-naphthoquinone (17) with β-nitrostyrene (18) is well-suited for comparison because it has already been studied while employing thiourea

• addition of 2-hydroxy-1,4-naphthoquinone to trans-β-nitrostyrene: To a stirred mixture of 2-hydroxy-1,4-naphthoquinone (34.8 mg, 0.2 mmol) and trans-β-nitrostyrene (32.8 mg, 0.22 mmol) in dry DCM (1.2 mL) was added catalyst 14a (11.8 mg, 0.02 mmol) and stirred for 3 h at room temperature. After completion

The regioselective synthesis of spirooxindolo pyrrolidines and pyrrolizidines via three-component reactions of acrylamides and aroylacrylic acids with isatins and α-amino acids

• Tatyana L. Pavlovskaya,
• Fedor G. Yaremenko,
• Victoria V. Lipson,
• Svetlana V. Shishkina,
• Oleg V. Shishkin,
• Vladimir I. Musatov and
• Alexander S. Karpenko

Beilstein J. Org. Chem. 2014, 10, 117–126, doi:10.3762/bjoc.10.8

• nonnatural α-amino acids [11][12][13], more than fifteen isatins [14], and 1,3-dipolarophiles, e.g. α,β-unsaturated ketones [15][16][17], maleimides [18][19], benzo[b]thiophene-1,1-dioxide [20], bis(arylmethylidene)acetones and -cycloalkanones [21][22], 1,4-naphthoquinone [23], arylidenemalonodinitriles [24

Thiourea-catalyzed Diels–Alder reaction of a naphthoquinone monoketal dienophile

• Carsten S. Kramer and
• Stefan Bräse

Beilstein J. Org. Chem. 2013, 9, 1414–1418, doi:10.3762/bjoc.9.158

• -Leopoldshafen, Germany 10.3762/bjoc.9.158 Abstract A variety of organocatalysts were screened for the catalysis of the naphthoquinone monoketal Diels–Alder reaction. In this study we found that Schreiner's thiourea catalyst 10 and Jacobson's thiourea catalyst 12 facilitate the cycloaddition of the sterically

• hindered naphthoquinone monoketal dienophile 3 with diene 4. The use of thiourea catalysis allowed for the first time the highly selective synthesis of the exo-product 2a in up to 63% yield. In this reaction a new quaternary center was built. The so formed cycloaddition product 2a represents the ABC

• ][8]. In our recent studies towards a synthetic access to the natural product beticolin 0 (1) [9] (Scheme 1), we have found that naphthoquinone monoketals are suitable building blocks for our designed synthesis [9]. In our retrosynthetic approach, the naphthoquinone monoketal dienophile 3 was found to