Rearrangements of organic peroxides and related processes

• Ivan A. Yaremenko,
• Vera A. Vil’,
• Dmitry V. Demchuk and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2016, 12, 1647–1748, doi:10.3762/bjoc.12.162

Biosynthesis of oxygen and nitrogen-containing heterocycles in polyketides

• Franziska Hemmerling and
• Frank Hahn

Beilstein J. Org. Chem. 2016, 12, 1512–1550, doi:10.3762/bjoc.12.148

• biosynthesis in Antirrhinum majus [152][153]. It catalyses the oxidation of phenols 180 and o-catechols 181 to o-quinones 182 and concomitant conjugate addition of a phenolic hydroxy group, leading to the formation of the central furan-3-one unit [154]. This enzyme is flavin-dependent and acts under

Regiodefined synthesis of brominated hydroxyanthraquinones related to proisocrinins

• Joyeeta Roy,
• Tanushree Mal,
• Supriti Jana and
• Dipakranjan Mal

Beilstein J. Org. Chem. 2016, 12, 531–536, doi:10.3762/bjoc.12.52

• condensation; Hauser annulation; proisocrinins; Introduction Anthraquinones constitute the largest group of naturally occurring quinones [1][2][3][4][5]. Isolated mainly from fungal sources, they display a wide range of biological activities which include anti-inflammatory, antifungal, antiparasidal, and

(Thio)urea-mediated synthesis of functionalized six-membered rings with multiple chiral centers

• Giorgos Koutoulogenis,
• Nikolaos Kaplaneris and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2016, 12, 462–495, doi:10.3762/bjoc.12.48

• tertiary amine-thiourea 56 was reported by Bernardi, Ricci and co-workers for the Diels–Alder reaction of 3-vinylindoles 51 (Scheme 18) [29]. The authors utilized either maleimides 52 or quinones 53 as the dienophile, affording the products 54 and 55 in excellent yields and enantioselectivities, after

Recent advances in N-heterocyclic carbene (NHC)-catalysed benzoin reactions

• Rajeev S. Menon,
• Akkattu T. Biju and
• Vijay Nair

Beilstein J. Org. Chem. 2016, 12, 444–461, doi:10.3762/bjoc.12.47

• . Although the presence of an isoxazole moiety is not a prerequisite for the success of this annulation, its rigid nature presumably renders the reaction highly stereoselective [47]. This simple and mild method allowed the construction of orthogonally protected polycyclic quinones from readily available

Natural products from microbes associated with insects

• Christine Beemelmanns,
• Huijuan Guo,
• Maja Rischer and
• Michael Poulsen

Beilstein J. Org. Chem. 2016, 12, 314–327, doi:10.3762/bjoc.12.34

• isolation and identification of many, including known, antimicrobial compounds. Among the reported structures are candicidin derivatives (e.g., candicidin D (8)) [79][80][81], actinomycin derivatives (e.g., actinomycin D (9)) [82], antimycin derivatives (e.g., antimycin A1 (10)), and novel quinones (e.g

2-Hetaryl-1,3-tropolones based on five-membered nitrogen heterocycles: synthesis, structure and properties

• Yury A. Sayapin,
• Inna O. Tupaeva,
• Alexandra A. Kolodina,
• Eugeny A. Gusakov,
• Vitaly N. Komissarov,
• Igor V. Dorogan,
• Nadezhda I. Makarova,
• Anatoly V. Metelitsa,
• Valery V. Tkachev,
• Sergey M. Aldoshin and
• Vladimir I. Minkin

Beilstein J. Org. Chem. 2015, 11, 2179–2188, doi:10.3762/bjoc.11.236

• convenient approach to the construction of seven-membered rings of 1,3-tropolone derivatives has been afforded by the acid-catalyzed reaction of o-quinones with methylene active compounds that proceeds with the expansion of the quinone six-membered ring [17][18][19][20]. The study of the reaction had been

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

Synthesis and spectroscopic properties of β-triazoloporphyrin–xanthone dyads

• Dileep Kumar Singh and
• Mahendra Nath

Beilstein J. Org. Chem. 2015, 11, 1434–1440, doi:10.3762/bjoc.11.155

• photoelectric materials [7][8]. In addition, porphyrins are potentially used as photosensitizers in photodynamic therapy to treat various types of tumors [9][10]. In recent years, many hybrid molecules including porphyrin–C60 [11], porphyrin–quinones [12] and porphyrin–cyclodextrin [13] conjugates were

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

Adsorption mechanism and valency of catechol-functionalized hyperbranched polyglycerols

• Stefanie Krysiak,
• Qiang Wei,
• Klaus Rischka,
• Andreas Hartwig,
• Rainer Haag and
• Thorsten Hugel

Beilstein J. Org. Chem. 2015, 11, 828–836, doi:10.3762/bjoc.11.92

• hyperbranched polyglycerol as a hydrophilic core with numerous DOPA (catechol) groups attached. A similar system has already proven to be advantageous for an antifouling coating on titanium oxide surfaces [21][22]. An added benefit of this system is that the oxidation of catechol to quinones makes crosslinking

Synthesis of tripodal catecholates and their immobilization on zinc oxide nanoparticles

• Franziska Klitsche,
• Julian Ramcke,
• Julia Migenda,
• Andreas Hensel,
• Tobias Vossmeyer,
• Horst Weller,
• Silvia Gross and
• Wolfgang Maison

Beilstein J. Org. Chem. 2015, 11, 678–686, doi:10.3762/bjoc.11.77

• conditions, the catechol moieties were reasonably stable and only small amounts (5%) of the corresponding oxidized quinones were detectable by NMR in the solutions after 24 h. The ZnO NPs were treated with the buffered catecholate solutions for 12 h, isolated by centrifugation, washed with a small amount of

Recent advances in the electrochemical construction of heterocycles

• Robert Francke

Beilstein J. Org. Chem. 2014, 10, 2858–2873, doi:10.3762/bjoc.10.303

• Michael addition/ring closure with in situ generated quinones (section 2.2) and sequential cyclizations involving acyliminium species and alkoxycarbenium ions (section 2.3) represent the majority of recently reported intermolecular electrochemical cyclizations. Cases which do not fall into any of these

The Ugi four-component reaction as a concise modular synthetic tool for photo-induced electron transfer donor-anthraquinone dyads

• Sarah Bay,
• Gamall Makhloufi,
• Christoph Janiak and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2014, 10, 1006–1016, doi:10.3762/bjoc.10.100

• moieties C60 fullerene [43][44][45], and quinones, such as 9,10-anthraquinone as a potential two electron acceptor, have been commonly used in Do–Acc arrangements [46][47][48][49][50][51]. In previous studies phenothiazine–anthraquinone couples have been introduced into peptide scaffolds [52][53][54] and

Recent advances in transition metal-catalyzed Csp²-monofluoro-, difluoro-, perfluoromethylation and trifluoromethylthiolation

• Grégory Landelle,
• Armen Panossian,
• Sergiy Pazenok,
• Jean-Pierre Vors and
• Frédéric R. Leroux

Beilstein J. Org. Chem. 2013, 9, 2476–2536, doi:10.3762/bjoc.9.287

• functionalized quinones. Both groups observed the inefficiency of Umemoto’s sulfonium reagents in this reaction, whereas Togni’s benziodoxolone reagent gave the best results. Y. Zhang, J. Wang and coworkers used 20 mol % of copper(I) iodide in a 1:1 t-BuOH/DCM solvent system at 55 °C with 2 equivalents of

Metal-free aerobic oxidations mediated by N-hydroxyphthalimide. A concise review

• Lucio Melone and
• Carlo Punta

Beilstein J. Org. Chem. 2013, 9, 1296–1310, doi:10.3762/bjoc.9.146

• the role of classical radical initiators obtained by thermal decomposition, we will focus on some intriguing redox systems, including nitric oxides, laccase, quinones and aldehydes, which allow operation under very mild conditions, offering efficient alternative solutions to the classical autoxidation

• contrast, laccase-NHPI and laccase-HBT systems, which follow a radical mechanism, showed high catalytic activity for the oxidation of ethers. Quinones and analogous derivatives As stressed before, the promotion of biological oxygenation is usually mediated by one-electron transfers, which lead to the

• formation of radicals. On the basis of this consideration, Xu and co-workers suggested that quinones, ubiquitous in nature and often involved in ET chains, could be employed to design biomimetic oxygenation models for the activation of NHPI [33]. The catalytic redox cycle is reported in Scheme 12. The one

Organocatalytic asymmetric Michael addition of unprotected 3-substituted oxindoles to 1,4-naphthoquinone

• Jin-Sheng Yu,
• Feng Zhou,
• Yun-Lin Liu and
• Jian Zhou

Beilstein J. Org. Chem. 2012, 8, 1360–1365, doi:10.3762/bjoc.8.157

• , together with our efforts in the synthesis of unsymmetric 3,3-diaryloxindoles [29], we try to develop a catalytic asymmetric method to enantioenriched 3,3-diaryloxindoles. In 2007, Jørgensen and coworkers pioneered the organocatalytic asymmetric addition reactions to quinones [30][31] which turned out to

• be a powerful strategy for the α-arylation of β-ketoesters and aldehydes. Inspired by their work, we anticipated that the catalytic asymmetric addition of 3-aryloxindoles to quinones would possibly install a hydroquinone moiety at the C3 position of oxindole to furnish the desired chiral 3,3

• -diaryloxindoles. It also came to our attention that, while the addition of 3-prochiral oxindole to a variety of Michael acceptors had been studied [32][33][34][35][36][37][38][39][40][41][42][43][44][45][46], the use of quinones as the Michael acceptor had not been realized. Therefore, in this letter we are going

Synthesis of 2a,8b-Dihydrocyclobuta[a]naphthalene-3,4-diones

• Kerstin Schmidt and
• Paul Margaretha

Beilstein J. Org. Chem. 2010, 6, No. 76, doi:10.3762/bjoc.6.76

• ; quinone monoacetals; Introduction The behaviour of excited 1,2- and 1,4-quinones towards ground-state molecules differs greatly. Whereas the former typically react via H-abstraction by an excited carbonyl group [1], the latter smoothly undergo [2 + 2] cycloaddition to alkenes to afford cyclobutane-type

Chiral amplification in a cyanobiphenyl nematic liquid crystal doped with helicene-like derivatives

• Alberta Ferrarini,
• Silvia Pieraccini,
• Stefano Masiero and
• Gian Piero Spada

Beilstein J. Org. Chem. 2009, 5, No. 50, doi:10.3762/bjoc.5.50

• variously distributed around the molecular core, allows us to extend our knowledge of the molecular origin of the chirality amplification in liquid crystals. Results and Discussion The enantioselective synthesis as well as the configuration assignment of enantiopure dihydro[5]helicene quinones or

• bisquinones 1–5 and of dihydro- (and tetrahydro-) [4]helicene quinones 6–8 has been described by Carreño, Urbano and coworkers [52][53][54][55][56][57]. The twisting powers of the helicenes under investigation measured in the nematic solvent E7 are reported in Table 1. We can see that all compounds possessing

• ” → “cholesteric P-handedness” already reported for a series of carbo- and hetero-helicenes [51]. (P)-7,8-Dihydro[5]helicene quinones or bisquinones 1–4 show moderate to high HTPs; despite the presence of the same tetracyclic core, derivative 5, with the tert-butyldimethylsilyl (TBDMS) blocking group, exhibits the

Progress in liquid crystal chemistry

• Sabine Laschat

Beilstein J. Org. Chem. 2009, 5, No. 48, doi:10.3762/bjoc.5.48

• quinones. Many new exciting discoveries in this diverse research area are to be expected in the near future and our aim with this Thematic Series is to attract a new audience to this topic. Sabine Laschat Guest Editor

Mitomycins syntheses: a recent update

• Jean-Christophe Andrez

Beilstein J. Org. Chem. 2009, 5, No. 33, doi:10.3762/bjoc.5.33

• requisite eight membered ring was formed by the well-established chemistry of quinones using an intramolecular Michael addition by the primary amine 157 (Scheme 44) [118]. The synthesis began with the known phenol 158 which was reacted with allyl bromide to trigger a Claisen rearrangement (Scheme 45). This

• this substrate in part due to the difficulties encountered during reduction of the methyl ester [124]. It is known that the treatment of quinones with mild reducing agents gives hydroquinones while strong reductants modify the quinone in a less specific manner [133][134]. 6.3. Remers. Synthesis of a

Diels- Alder reactions using 4,7-dioxygenated indanones as dienophiles for regioselective construction of oxygenated 2,3-dihydrobenz[f]indenone skeleton

• Natsuno Etomi,
• Takuya Kumamoto,
• Waka Nakanishi and
• Tsutomu Ishikawa

Beilstein J. Org. Chem. 2008, 4, No. 15, doi:10.3762/bjoc.4.15

• -opened product 27. Transition states supposed for the regioselective DAR via quinone route. Representative LUMO coeffients of quinones 8 and 12 (a) and their reaction courses with diene 7 (b). Retrosynthesis of kinamycins. Synthesis of quinones 8 and 12 and the acetals 13 and 14. Reagents and conditions

Variations in product in reactions of naphthoquinone with primary amines

• Marjit W. Singh,
• Anirban Karmakar,
• Nilotpal Barooah and
• Jubaraj B. Baruah

Beilstein J. Org. Chem. 2007, 3, No. 10, doi:10.1186/1860-5397-3-10

• the sole product in the reaction. Background Amino quinones are used as medicines, [1][2][3] herbicides [4] and they also show interesting redox switching properties. [5] Amino quinones are formed in the reactions of different amines with quinones. [6][7][8][9][10][11][12][13] For example 1,4

• -benzoquinone reacts with primary amines to give 2,5-diamino 1,4-benzoquinones; similar reaction of 1,4-naphthoquinone with primary amines results in the formation of 2-amino 1,4-naphthoquinones. [13] However, the product formed from such simple reaction of amine with various quinones has much scope for

Effect of transannular interaction on the redox- potentials in a series of bicyclic quinones

• Grigoriy Sereda,
• Jesse Van Heukelom,
• Miles Koppang,
• Sudha Ramreddy and
• Nicole Collins

Beilstein J. Org. Chem. 2006, 2, No. 26, doi:10.1186/1860-5397-2-26

• redox-potentials of bicyclo[2.2.2]octane-derived quinones will help in the design of new compounds with controlled biological activity. However, attempts to directly relate the reduction potentials of substituted triptycene-quinones to the electronic effects of substituents are often unsuccessful

• . Results First and second redox-potentials of a series of bicyclic quinones are compared to computed energies of their LUMO, LUMO+1, and energies of reduction. Transannular influence of substituent on the redox-potentials is rationalized in terms of MO theory. Acetoxy-substituents in the 5,8-positions of

• the triptycene-quinone system selectively destabilize the product of the two-electron reduction. Conclusion We have shown that first redox-potentials of substituted bicyclic quinones correlate with their calculated LUMO energies and the energies of reduction. The second redox-potentials correlate with

The Elbs and Boyland- Sims peroxydisulfate oxidations

• E. J. Behrman

Beilstein J. Org. Chem. 2006, 2, No. 22, doi:10.1186/1860-5397-2-22

• the intermediate sulfate esters using acetic acid which spares carboxylic esters. These authors also give a current example of the use of sulfate esters as a protecting group in synthesis [7] as do Bunnett and Jenvey. [8] Parenthetically, there is a disputed report of the formation of quinones in low

• - and p-benzoquinone where the difference in the redox potential is 0.07 V [11] corresponding to 3 kcal mol-1. It may also be relevant that quinones are subject to attack by the hydroxyl ion to form (eventually) humic acids and that o-quinones are more reactive than p-quinones. [12][13] An analogous