Heterocyclic quinones

A number of benzimidazole-4,5(6,7)-quinones containing a secondary amine residue in the quinone ring were obtained by oxidation of N-substituted 5(6)-hydroxybenzimidazoles with oxygen in the presence of copper(II)-piperidine (dimethylamine) complexes. It is shown that the reaction proceeds in the presence of catalytic amounts of copper acetate and is not accompanied by animation of the C₍₂₎ atom.See [1] for communication XXXII.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1680–1683, December, 1978.     

A facile route to isoflavone quinones via the direct cross-coupling of chromones and quinones

A straightforward and efficient method for the palladium-catalyzed direct cross-coupling of chromones with various quinones has been developed to rapidly construct isoflavone quinone structural motifs.     

Natural quinones

Summary A new anthraquinone of composition C₁₇H₁₄O₅, mp 182–183° (decomp., from benzene) has been isolated from the roots ofRubia iberica (Fisch. ex D.C.); it has been called ibericin and has the structure of 1, 3-dihydroxy-4-ethoxy-methylanthraquinone.Khimiya Prirodnykh Soedinenii, Vol. 2, No. 1, pp. 12–15, 1966     

Heterocyclic quinones

It is shown that 2,4-bis(dialkylamino)benzothiazole-6,7-quinones are formed by the oxidation of 6-hydroxybenzothiazole in the presence of a Cu²⁺-secondary amine complex. The mechanism of the formation of the compounds obtained is discussed.See [13] for communication XI.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 196–200, February, 1971.     

Heterocyclic quinones

Oxidation of substituted 4-amino-6-hydroxyquinaldines and 4-chloro-6-hydroxiquinaldine with oxygen in the presence of Cu⁺⁺-secondary amine complexes has yielded a new group of compounds, substituted 4-aminoquinoline-5,6-quinones. The reaction intermediate, 4-chloroquinaldine-5,6-quinone, has been prepared and oxidized. The effects of substituents on the course of the oxidation have been examined, and some properties of the compounds obtained have been investigated.For part VIII, see [1].Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 6, No. 5, pp. 637–641, May, 1970.     

Regioselectivities of Diels-Alder cycloadditions to methoxy-substituted quinones

Diels-Alder cycloadducts of unsymmetrical electron-rich dienes and methoxybenzoquinones or naphthoquinones produce adducts in which the more nucleophilic diene terminus becomes bonded to the non-methoxylated carbon. These results support the “secondary orbital”, but not the “schizophrenic”, model for donor substituent effects on regioselectivity.     

Fluoride-induced cyclization of pentacenequinone to higher quinones

Novel pentacenequinone derivatives 3, 7, and 10 have been synthesized via Suzuki-Miyaura coupling. Derivatives 3 and 7 having OTBS groups undergo irreversible fluoride-induced cyclization to substituted higher quinones in the presence of TBAF in dry THF using one-pot, two-step strategies in moderate yields. These functionalized higher quinone derivatives are freely soluble in THF and DMSO and can be used as precursors for the synthesis of higher acene derivatives.     

Studies on quinones

Phenanthro[1, 2-c][1, 2, 5]oxadiazole-10, 11-dione (phenanthrene quinone furazan, I), like anthraquinone furazan, is capable of adding nucleophilic agents to carbon atom 4 of the carbon skeleton or to the oxygen of the carbonyl group. Thus, its reactions with thiophenol and benzenesulfinic acid, with subsequent oxidation lead, respectively, to the substituted quinones II and IV, the latter of which is converted by the action of benzenesulfinic acid into the benzenesulfonic ester V.For part IX, see [1]     

Investigation of quinones

Naphtho[2,3-f]quinoxaline-7,12-diones add a molecule of benzenesulfinic acid to give 5-phenylsulfonyl-7, 12-dihydroxynaphtho[2,3-f]quinoxalines. The latter are oxidized to 5-phenylsulfonyl-substituted quinones, which add a molecule of benzenesulfinic acid to the oxygen atoms of the quinone grouping to give the O⁷-benzenesulfonate of 5-phenylsulfonyl-7, 12-dihydroxynaphtho[2,3-f]quinoxaline. The protonated form of naphtho[2,3-f]quinoxa-line-7, 12-dione, which is stabilized by an intramolecular hydrogen bond, as confirmed by the anomalously high basicity of angular naphtho[2,3-f]quinoxaline-7,12-dione as compared with its linear isomer, which is inert in reactions with benzenesulfinic acid, undergoes reaction.     

Researches on quinones

When anthra[1,2,5]oxadiazole-6, 11-dione reacts with sodium bisulfite, the sulfonic group enters at position 4 in the ring, giving 6, 11-dihydroxyanthra[1,2-c][1,2,5]oxadiazole-4-sulfonic acid. The latter compound is also formed by treating with bisulfite anthra[1,2-c]-[1,2,5]oxadiazole-6, 11-dione-5-sulfonic acid, obviously initially converted to the 4-sulfonic acid by addition-elimination of a molecule of bisulfite. The formation of sulfuric monoester observed in the course of the work in the reaction of quinone with bisulfite, is an example of an addition of a type unusual for carbonyl compounds, where a nucleophilic reagent, the sulfite ion, adds to carbonyl oxygen.For Part II see [1].     

Building photoactive molecular-scale wires

Polyalkynylene groups are known to function as excellent electronic conductors at the molecular level. Such moieties have now been used to interconnect redox and photoactive transition metal oligopyridine complexes so that the efficiency of light-induced energy or electron transfer along the molecular axis can be monitored. The important issues that control the effectiveness of electronic coupling through the alkyne are discussed. In particular, attention is given to separating the effects of electron delocalization within the triplet manifold from the more general decoupling of metal-centered and charge-transfer excited states that occurs upon lowering the triplet energy. The role of the auxiliary ligands is considered, as is the effect of nuclearity. Similarly, the size of the nuclear reorganization energy has to be taken into account in a proper discussion of the photophysical properties of such systems. A second issue of importance to the design of photoelectronic devices concerns the use of interspersed groups to modulate the electronic coupling properties of the alkyne spacer. Such electron relays may be aryl hydrocarbons or platinum bis-acetylides, both groups being able to curtail electron flow along the molecular axis.     

Investigation of quinones

The action of primary and secondary amines on 2-arylanthraquinonetriazoles results in substitution of the hydrogen atom in the 4 position to form 4-amino derivatives. The activity of 2-arylanthraquinonetriazoles in amination is less than that of the previously studied anthraquinone-1, 2,5-X-diazoles (X=O, S, Se). This is explained by the electron-donor effect of the aryl group in the 2 position and the lower degree of alternation of the bonds in the ring adjacent to the heteroring, which leads to a decrease in the effectiveness of transmission of the electron-acceptor effect to the reaction center in the 4 position.See [1] for communication XXVI.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1574–1580, November, 1971.     

Studies on quinones

Anthra[1,2-c][1,2,5]oxadiazole-6,11-dione (I) was added to benzenesulfinic acid and thiophenol with the formation of 4-phenyl-sulfonyl- and 4-phenylmercapto-substituted hydroquinones, which on oxidation were converted into the corresponding quinones III and VII. 4-Phenylsulfonylanthra[1,2-c][1,2,5]oxadiazole-6,11-dione (III), in turn, reacted readily with benzenesulfinic acid, adding a molecule of the latter to the carbonyl oxygen atom and was converted into the O-benzenesulfonic monoester [6] (IV). Using compounds IV and hydroxynaphtho[1,2-c][1,2,5]oxadiazole (XId) the capability of the nitrogen atom of the furazan ring of participating in the formation of intramolecular hydrogen bonds was shown.     

Investigation of quinones

The reaction of naphtho[2,3-a]phenazine-8,13-dlone (I) with hydrogen chloride leads, depending on the solvent, to 2- or 6-ehlorodihydroazines, which are converted to 2,6-dichloro derivatives after oxidation and retreatment with hydrogen chloride; the corresponding 6-amino-substituted naphthophenazinediones are formed by reaction with amines. The direction of nucleophilic attack in these reactions is caused by the coordinated electron-acceptor effect of the peri-oriented oxygen atoms of the quinone grouping and the heterocyclic nitrogen and by intensified protonation with the closing of an intramolecular hydrogen bond.See [7] for communication XXIV.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1139–1144, August, 1971.     

Studies on quinones

Anthra[1,2-c]-1,2,5-oxadiazole-6,11-dione (I) readily reacts with ammonia and primary and secondary amines, being converted with a yield of about 80–83% into the corresponding 4-amino derivatives of antnra[1,2-c]-1,2,5-oxadiazole-6,11-dione(III).For part VI, see [1].     

Investigation of heterocyclic quinones

3,5-Bis(dialkylamino)isoquinoline-7,8-quinones are formed by oxidative amination of 7-hydroxyisoquinoline. The o-quinones are converted to 3-piperidino(morpholino)-7-hydroxy (methoxy) isoquinoline-5,8-quinones.See [1] for communication XXIII.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1253–1256, September, 1974.     

Research on heterocyclic quinones

7-Hydroxy-1-isoquinolones, 3-methyl-7-hydroxyisoquinoline, and 6-hydroxyisoquinoline were synthesized, and their reactions, as well as the reaction of 7-methoxyisoquinoline-5,8-quinone, with amines were studied. The problem of the transmission of the mesomeric and inductive effects of the quinone carbonyl groups through the heteroring and the increase in the electrophilicities of the quinones upon chelate formation are discussed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 500–505, April, 1977.     

Electron transfer from aromatic amino acids to triplet quinones

The photoreduction of 1,4-benzoquinone, 1,4-naphthoquinone, 9,10-anthraquinone (AQ) and several methylated or halogenated derivatives in argon-saturated acetonitrile-water mixtures by indole, N-acetyltryptophan and N-acetyltyrosine was studied by time-resolved UV-vis spectroscopy using 20 ns UV laser pulses. The quinone triplet state is quenched by the aromatic amino acids and the rate constants are (1-5)x10(9)M(-1)s(-1). The semiquinone radical anion Q.(-) is the major observable transient after electron transfer from amino acids to the quinone triplet state. Termination of Q.(-) and amino acid derived radicals takes place in the mus-ms range. The effects of structure and other specific properties of quinones and amino acids are discussed. The radicals are subjects of intercept with oxygen, whereby hydrogen peroxide is eventually formed. The quantum yield of oxygen uptake Phi(-O2) as a measure of formation of hydrogen peroxide increases with increasing amino acid concentration, approaching Phi(-O2) for AQ in air-saturated solution.