Construction of diazepine-containing spiroindolines via annulation reaction of α-halogenated N-acylhydrazones and isatin-derived MBH carbonates

• Xing Liu,
• Wenjing Shi,
• Jing Sun and
• Chao-Guo Yan

Beilstein J. Org. Chem. 2023, 19, 1923–1932, doi:10.3762/bjoc.19.143

• efficient synthesis of spiro[azepine-4,3'-indoline] derivatives via the [4 + 3] cycloaddition reaction of bromo-substituted isatin-derived MBH adducts and N-(o-chloromethyl)arylamides. In this efficient protocol, the reactive allylic phosphonium ylides and aza-o-quinone methides were generated in situ and

• )benzenesulfonamides to give chiral azepane spirooxindoles with excellent stereoselectivity (reaction 2 in Scheme 1) [55][56]. Du and co-workers reported a DABCO-mediated [4 + 3] cycloaddition reaction between o-quinone methides and isatin-derived MBH carbonates to give functionalized benzo[b]oxepine derivatives in

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

• oxidative organocatalysis. Electrochemical DDQ-catalyzed intramolecular dehydrogenative aryl–aryl coupling. DDQ-mediated cross-dehydrogenative C–N coupling of benzylic substrates with azoles. Biomimetic o-quinone-catalyzed benzylic alcohol oxidation. Electrochemical synthesis of secondary amines by

Site-selective reactions mediated by molecular containers

• Rui Wang and
• Yang Yu

Beilstein J. Org. Chem. 2022, 18, 309–324, doi:10.3762/bjoc.18.35

• mixture of different products will form through various pathways [50][51][52][53]. By applying the cage host A, the authors realized a highly site-selective radical addition reaction of o-quinone 10 and substituted toluene 11, giving rise to the unusual 1,4-adduct 15 (Figure 3) [54]. Specifically, upon

• naphthalene and phthalimide mediated by cage host A. Cage host A-mediated selective 1,4-radical addition of o-quinone 10. Cyclodextrin-mediated site-selective reductions. Selective reduction of an α,ω-diazide compound mediated by water-soluble cavitand D. Selective radical reduction of α,ω-dihalides mediated

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

• reaction probably occurs in the o-quinone moiety group. Subsequently, Obo [46] demonstrated that the reaction of β-NQSNa (18) and glycine ethyl ester form 19 in a 46% yield, indicating that the reaction occurred at C4 (Scheme 2). Fu and co-workers [47] prepared a new electrochemical sensor for the specific

Transition-metal-free intramolecular Friedel–Crafts reaction by alkene activation: A method for the synthesis of some novel xanthene derivatives

• Tülay Yıldız,
• İrem Baştaş and
• Hatice Başpınar Küçük

Beilstein J. Org. Chem. 2021, 17, 2203–2208, doi:10.3762/bjoc.17.142

• performed for the first time using TFA. The reasonable mechanism of this reaction is delineated in Scheme 2. Despite this reaction occurring by the classical Friedel–Crafts mechanism, we believe that o-quinone methide is formed as an intermediate. Because of its very reactive structure, most of the xanthene

• synthesis is based on the o-quinone methide intermediate [54][55][56][57][58]. The carbocation formed by the activation of an alkene with acid turns into an intermediate o-quinone methide, resulting in a successful cyclization. As seen in the mechanism, the acid catalyst adds to the vinyl group, allowing

• the formation of a tertiary carbocation. The carbocation is then transformed into the o-quinone methide intermediate, which undergoes cyclization to yield 9-methyl-9-arylxanthene by aromatization. When the yields of the synthesized compounds are examined, it is seen that the yields are high when there

Asymmetric organocatalyzed synthesis of coumarin derivatives

• Natália M. Moreira,
• Lorena S. R. Martelli and
• Arlene G. Corrêa

Beilstein J. Org. Chem. 2021, 17, 1952–1980, doi:10.3762/bjoc.17.128

• -hydroxycoumarin (1) with the chiral catalyst 48, as shown in Scheme 15 [48]. The enantioselective synthesis of dihydrocoumarins 51 from an inverse demand [4 + 2] cycloaddition of ketenes 50 with o-quinone methides 49 using carbene catalyst (NHC) 52 was described by Ye and co-workers [49].This transformation

Organocatalytic asymmetric Michael/acyl transfer reaction between α-nitroketones and 4-arylidenepyrrolidine-2,3-diones

• Chandrakanta Parida and
• Subhas Chandra Pan

Beilstein J. Org. Chem. 2021, 17, 1447–1452, doi:10.3762/bjoc.17.100

• the keto group [11][12][13]. Consequently, our group developed an organocatalytic asymmetric Michael–acyl transfer reaction of α-nitroketones with unsaturated pyrazolones, 2-hydroxycinnamaldehydes, γ/δ-hydroxyenones, o-quinone methides, etc. [14][15][16][17][18]. Other groups also contributed

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

• -quinones. A study of their monoreduced semiquinone derivatives reveal that the spin density is delocalized across the whole molecule, including peripheral fragments. The first stable o-quinone derivative bearing an annulated thiete heterocycle has been isolated and characterized. Keywords: dioxolene

• ligand; 1,3-dithiole; ditopic ligand; o-quinone; thiete; Introduction There are a number of methods which may be used for the synthesis of new o-quinones in order to vary their redox properties and coordination abilities. The key features of o-quinones are redox activity as well as chelating

• 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

An overview of the cycloaddition chemistry of fulvenes and emerging applications

• Ellen Swan,
• Kirsten Platts and
• Anton Blencowe

Beilstein J. Org. Chem. 2019, 15, 2113–2132, doi:10.3762/bjoc.15.209

• reaction, causing the formation of complex products. Examples of dienes that have previously been used include cyclic diketones (o-benzoquinones) (Scheme 15, reaction pathways (i)) [60][89][156][157][158][160][161][162][163][164][165][211][215][226], o-quinone methides [87], o-xylylenes [125][153

Oxidative dehydrogenation of C–C and C–N bonds: A convenient approach to access diverse (dihydro)heteroaromatic compounds

• Santanu Hati,
• Ulrike Holzgrabe and
• Subhabrata Sen

Beilstein J. Org. Chem. 2017, 13, 1670–1692, doi:10.3762/bjoc.13.162

• , phd = 1,10-phenanthroline-5,6-dione. Oxidative dehydrogenation with Flavin mimics. o-Quinone based bioinspired catalysts for the synthesis of dihydroisoquinolines. Cobalt-catalyzed aerobic dehydrogenation of Hantzch 1,4-DHPs and pyrazolines. Mechanism of cobalt-catalyzed aerobic dehydrogenation of

Protonated paramagnetic redox forms of di-o-quinone bridged with p-phenylene-extended TTF: A EPR spectroscopy study

• Nikolay O. Chalkov,
• Vladimir K. Cherkasov,
• Gleb A. Abakumov,
• Andrey G. Starikov and
• Viacheslav A. Kuropatov

Beilstein J. Org. Chem. 2016, 12, 2450–2456, doi:10.3762/bjoc.12.238

• State University, Gagarina av., 23, Nizhny Novgorod, Russia Southern Scientific Center of Russian Academy of Science, 344006, Chekhov str., 41, Rostov-on-Don, Russia 10.3762/bjoc.12.238 Abstract The chemical oxidation and reduction processes of deprotonated, direduced o-quinone-exTTF-o-quinone in

• -extended tetrathiafulvalene connector provides a quite effective electronic communication channel between dioxolene coordination sites. It was found that the deprotonated, direduced o-quinone-exTTF-o-quinone is capable to reduction of the metal copper in solution. The radical anion species formed in this

• ; EPR spectroscopy; extended tetrathiafulvalene; protonated semiquinone; Introduction The main idea that led to the creation of the system constructed of two o-quinone terminal moieties bridged with annulated extended tetrathiafulvalene (TTF) insertion, was an attempt to explore acceptor–donor–acceptor

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

• -tetrachloro-1,3-tropolone [25][26], but no comprehensive study of the mechanism of the expansion of the o-quinone rings in this reaction has yet been undertaken. Therefore, one of the purposes of the present work was to gain insight into the major details of the mechanism of the formation of 5,6,7-trichloro

• -chloranil affords the intermediate adducts, 6-(2-hetarylmethylene)-6-hydroxy-2,4-cyclohexadiene-1-ones 7. Such type intermediates were isolated and structurally characterized in the reactions of 2-methylquinoline with 3,5-di-tert-butyl-o-quinone [19] and benzophenones with o-chloranil [22]. The addition of

• a methylene group of bismuthonium 2-oxoalkylides to a carbonyl carbon of an o-quinone ring is also considered to be the primary stage of the reaction leading to the formation of derivatives of 2-acyl-1,3-tropolones [27]. As shown previously [19] and in the present study as well, the essential ring

Pyridinoacridine alkaloids of marine origin: NMR and MS spectral data, synthesis, biosynthesis and biological activity

• Louis P. Sandjo,
• Victor Kuete and
• Maique W. Biavatti

Beilstein J. Org. Chem. 2015, 11, 1667–1699, doi:10.3762/bjoc.11.183

• -acetyldopamine (B) into an O-quinone derivative which reacted itself with the arylamine (A) through a Michael addition mechanism and the acridine core was formed via a nucleophilic condensation process. The addition step was also facilitated by CeCl3 used here as a Lewis acid. The last step, characterized by the

Selected synthetic strategies to cyclophanes

• Sambasivarao Kotha,
• Mukesh E. Shirbhate and
• Gopalkrushna T. Waghule

Beilstein J. Org. Chem. 2015, 11, 1274–1331, doi:10.3762/bjoc.11.142

• -workers [198] have reported the synthesis of sporolide B (349). The synthesis involves a DA reaction between o-quinone as the diene component and indene derivatives as dienophiles. This total synthesis also involves a

Asymmetric synthesis of a highly functionalized bicyclo[3.2.2]nonene derivative

• Toshiki Tabuchi,
• Daisuke Urabe and
• Masayuki Inoue

Beilstein J. Org. Chem. 2013, 9, 655–663, doi:10.3762/bjoc.9.74

• -dimethylbenzene-1,4-diol (3) and maleic anhydride lead to the construction of bicyclo[2.2.2]octene 4, which was then transformed into racemic 2 through electrolysis [11]. Alternatively, the Diels–Alder reaction between 3,6-dimethyl-o-quinone monoacetal 5 and 1,1-diethoxyethylene provided bicyclo[2.2.2]octene 6

Studies on polynuclear furoquinones. Part 1: Synthesis of tri- and tetra- cyclic furoquinones simulating BCD/ABCD ring system of furoquinone diterpenoids

• Faruk H. Shaik and
• Gandhi K. Kar

Beilstein J. Org. Chem. 2009, 5, No. 47, doi:10.3762/bjoc.5.47

• acid (TFA) and trifluoroacetic anhydride (TFAA) at room temperature in 71% yield. The phenol 12 was finally oxidized (with Fremy’s salt) [36][37][38] to the o-quinone 13 to complete the synthesis of phenanthro[1,2-b]furan-10,11-dione. The compounds were characterized by usual spectroscopic and

Mitomycins syntheses: a recent update

• Jean-Christophe Andrez

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