13C-NMR.-Substituenteninkremente der N3-Gruppe in Azido-1,4-benzochinonen

¹³C-NMR. Substituent Increments of the Azido-group in 1,4-Benzoquinones The empirical substituent increments of the azido-group in 1,4-benzoquinones have been derived from the ¹³C-NMR. chemical shifts of 2-azido-5-chloro-1,4-benzoquinone. The validity of the obtained values was tested by comparison of the empirical and computed ¹³C-NMR. chemical shifts of other azido-chloro-1,4-benzoquinones.     

Ring-fluorinated naphthalene and indene synthesis via 6- and 5-endo-trig cyclizations of gem-difluoroalkenes by carbon nucleophiles

The intramolecular vinylic substitution of gem-difluoroalkenes is accomplished with sp³ and sp² carbon nucleophiles (2-arylethyllithium and aryllithium) in a 6-endo-trig and a normally disfavored 5-endo-trig fashion, leading to the synthesis of 3-fluoro-1,2-dihydronaphthalenes and 3-fluoroindenes, respectively. The dihydronaphthalenes are readily aromatized on treatment with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) to afford 2-fluoronaphthalenes.     

Mini Review of Sulfur Heterocyclization from π-Electron Deficient Quinones via Charge-Transfer Interaction

Abstract

This survey is mainly concerned with selected reactions of 2,3-dichloro-1,4-naphthoquinone (DHNQ), 3,4,5,6-tetrachloro-1,2-benzoquinone (o-CHL), 2,3,5,6-tetrachloro-1,4-benzoquinone (p-CHL), and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as π-deficient quinones that are used or offer potential use for sulfur heterocyclic synthesis. Reaction of various donors with the π-deficient quinones are studied, especially those via charge-transfer complex formation.     

Investigation of electrochemically induced Michael addition reactions. Oxidation of some dihydroxybenzene derivatives in the presence of azide ion

In aqueous solution containing azide ion as a nucleophile, electrochemical oxidation of hydroquinone and some dihydroxybenzoic acids have been studied using cyclic voltammetry and controlled-potential coulometry. The voltammetric data show that electrochemically generated para and ortho-benzoquinones participate in Michael addition reactions with azide ions to form the corresponding diazido or diaminobenzoquinones. In this work, we have proposed various mechanisms for the electrode process and we report an efficient and one-pot method for the synthesis of 2,5-diazido-1,4-benzoquinone, 2,5-diamino-1,4-benzoquinone, 4,5-diamino-1,2-benzoquinone, and 2,3-diamino-5,6-dioxocyclohexa-1,3-dienecarboxylic acid based on the Michael reaction of electrochemically generated ortho and para-benzoquinones with azide ion in an undivided cell using an environmentally friendly reagent-less method in ambient conditions. An estimation of the observed homogeneous rate constant (k_obs) of the reaction of electrochemically generated para-benzoquinone with azide ion by the digital simulation method is also presented.     

Synthesis of 5-hydroxy-N-(2-vinyloxyalkyl)indoles from dicarbonyl compounds and vinyloxyalkylamines

N-(Vinyloxyalkyl)enaminoketones were obtained by the condensation of vinyloxyalkylamines with acetylacetone or ethyl acetoacetate. Their subsequent reactions with 1,4-benzoquinone produce the corresponding 5-hydroxy-2-methyl-N-(2-vinyloxyalkyl)indoles in 17–43% yields. The structures of the compounds obtained were confirmed by IR and¹H NMR spectroscopy.     

Synthesis of sulfur-containing heterocycles through oxidative carbon-hydrogen bond functionalization

Vinyl sulfides react rapidly and efficiently with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) to form α,β-unsaturated thiocarbenium ions through oxidative carbon-hydrogen bond cleavage. These electrophiles couple with appended π-nucleophiles to yield sulfur-containing heterocycles through carbon-carbon bond formation. Several nucleophiles are compatible with the procedure, and the reactions generally proceed through readily predictable transition states.     

Characterization and thermal kinetic studies on charge-transfer complexes of 4,4′-bipyridine with benzoquinone derivatives

4,4′-Bipyridine belong to an important class of compounds with wide applications in different fields and since the formation charge transfer compounds give opportunity to improve the physical and chemical properties of different donors so charge transfer compounds of 4,4′-bipyridine (Bpy) with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone [chloranilic acid] (CHA) and 2,3,5,6-tetrachloro-1,4-benzoquinone [choloranil] (CHL) were studied. The stoichiometries of the reactions were determined from photometric titration methods. Although the thermodynamic parameters [Gibbs free energy (ΔG°), enthalpy (ΔH°), and entropy change (ΔS°)] were calculated. The thermal decomposition of the complexes follows first order kinetics and thermodynamic parameters of the decomposition were calculated. The structural morphology was investigated by scanning electron microscopy (SEM) and Transmission Electron Microscopy (TEM) and show that these molecules are of nanosize.     

Chemistry of O-Benzoquinones and Masked O-Benzoquinones I. Diels-Alder Reactions of O-Benzoquinones with Dimethyl Acetylenedicarboxylate and Phenylacetylene

Diels-Alder reactions of six o-benzoquinones with dimethyl acetylenedicarboxylate has been examined. The yields of adducts vary with the natures of the o-benzoquinones, 3,4-Di-n-propyl-(1c), 3,6-di-n-propyl (1d). 3. 4-diallyl-(1e) and 3, 6-diallyl-o-benzoquinone (1f) are found to give bicyclic a-diketones exclusively without the formation of 1,4-dioxine derivatives, the yields ranging from 20 to 70%. In the case of 4, 5-dimethoxy-o-benzoquinone, dimethyl 4, 5-dimethoxyphthalate is produced in 42% yield, presumably derived from the decomposition of the corresponding initially formed α-diketone. 3, 6-Di-n-propyl-4, 5-dimethoxy-o-benzoquinone deteriorates without addition to dimethyl acetylenedicarboxylate upon heating. The additions of o-benzoquinones 1c , 1d and 1f to phenylacetylene are also studied. The yields of adducts, α-diketones, range from 23% to 82%.     

Alkoxylation of 3,6-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-1,2-benzoquinone. New bis-1,2-benzoquinones

Alkoxylation of 3,6-di-tert-butyl-1,2-benzoquinone with a number of diols, including propane-1,3-diol, butane-1,4-diol, di-, and triethylene glycols, and cyclohexane-1,4-diyldimethanol, was studied. Nine new 4-alkoxy-3,6-di-tert-butyl-1,2-benzoquinones were synthesized, four of which were bis-1,2-benzoquinones with different tethers (6–13 atoms) between the quinone fragments. Depending on the length of the chain between the hydroxy groups in glycols, bicyclic 4,5-disubstituted 3,6-di-tert-butyl-1,2-benzoquinones were formed or their stepwise alkoxylation occurred. The newly synthesized o-benzoquinone derivatives can be reduced with alkali metals to give radical anions and converted into semiquinone chelates with manganese carbonyl.     

Synthesis of benzoquinone derivatives containing benzotriazole fragments

2,3,5,6-Tetrakis(1H-benzotriazol-1-yl)-1,4-benzoquinone was synthesized in 85% yield by reaction of 2,3,5,6-tetrachloro-1,4-benzoquinone with 1H-benzotriazole in pyridine at room temperature. Treatment of 2,3,5,6-tetrakis(1H-benzotriazol-1-yl)-1,4-benzoquinone with piperidine, ω-amino acids, and aromatic amines gave the corresponding 2,5-diamino-3,6-bis(1H-benzotriazol-1-yl)-1,4-benzoquinones.     

Iron pentacarbonyl assisted photochemical route to 2,5- and 2,6-divinyl-substituted 1,4-benzoquinones from 1-ene-3-ynes

Photochemical reaction between the enynes, (Z)-1-methoxybut-1-ene-3-yne, 1 or isopropenyl acetylene, 2 with CO in presence of Fe(CO)₅ yields the 2,6- and 2,5-divinyl-substituted 1,4-benzoquinones: 2,6-bis{(Z)-2-methoxyvinyl}-1,4-benzoquinone (3, 42%), 2,5-bis{(Z)-2-methoxyvinyl}-1,4-benzoquinone (4, 31.5%), [{η²,η²:2,6-di(prop-1-en-2-yl)-1,4-benzoquinone}tricarbonyliron] (5, 45%), and {η²,η²:2,5-di(prop-1-en-2-yl)-1,4-benzoquinone}tricarbonyliron] (6, 65%).     

Carbazoledioxazines having long alkyl groups. 2. Synthesis of carbazoledioxazines with angular type structure

Carbazoledioxazines with an angular type structure (5,15-dialkyl-7,17-dialkyloxy-9,19-dichloro-5,15-dihydrodiindolo[2,3-c:2′,3′-n]triphenodioxazines) were selectively synthesized by electrochemical oxidative ring closure of precursors (2,5-bis(9-alkyl-2-alkyloxy-3-carbazolylamino)-3,6-dichloro-1,4-benzoquinones). The structure was confirmed by ¹H-nmr and other instrumental analyses. Their thermal properties and solubilities were investigated and were compared with those of carbazoledioxazines with a linear type structure.     

Synthesis of Bicyclo[4.2.0]Octa-3,7-Diene-2,5-Diones

The bicyclo[4.2.0]octa-3,7-diene-2,5-diones (1) are of interest in that they are valence isomers of 1,4-cyclooctatetraenoquinones. The most obvious route for the formation of such compounds is the [2+2] photoaddition of alkynes to p-benzoquinones. Such a reaction has been observed in the case of 1,4-naphthoquinones. With p-benzoquinones, however, it has been observed in the case of 2-methoxy-p-benzoquinone (2a) alone, while p-benzoquinone (2b) and chloranil (2c) give products derived from addition of acetylenes to a carbonyl rather than an ethylenic bond; ^3,4 such products also accompany the products from 1,4-naphthoquinones referred to above.^1,3     

Synthesis of aromatic polyesters and polyamides by alternating copolymerizations of 1,4-dicarbonyl-1,4-dihydronaphthalene with bezoquinones and benzoquinone diimines

1,4-Dicarbonyl-1,4-dihydronaphthalene ( 1 ) was synthesized by the dehydrochlorination reaction of 1,4-dihydronaphthalene-1,4-dicarbonyl chloride with triethylamine and obtained as its very dilute solution, but it easily polymerized in the concentration as high as 0.1 mol/L to give its polymer. 1 generated in situ by the dehydrochlorination reaction of 1,4-dihydronaphthalene-1,4-dicarbonyl chloride in a deoxygenated toluene polymerized alternatingly with benzoquinones such as 2-dodecylthio-p-benzoquinone, 2,5-di(tert-butyl)-p-benzoquinone, p-benzoquinone, and 2,3-dichloro-5,6-dicyano-p-benzoquinone, and with benzoquinone diimines such as N,N′-diethoxycarbonyl-p-benzoquinone diimine, N,N′-dibenzoyl-p-benzoquinone diimine, and N,N′-diphenyl-p-benzoquinone diimine to give aromatic polyesters and polyamides, respectively. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1929–1936, 1998     

质体醌类似物的合成研究——Ⅰ.不同侧链的质体醌类似物

本文通过对2,3-二甲基-1,4-苯醌与脂肪酸在过硫酸铵及硝酸银作用下发生的自由基烷基化反应,合成了九种新的具有不同长短侧链的质体醌类似物。其结构已经IR,UV,~1H NMR和MS证实。     

Some Novel Quinone-Type Compounds Containing Arylseleno Groups Derived from Tetrachloro-1, 4-Benzoquinone and 2, 3-Dichloro-1, 4-Naphthoquinone

Tetrachloro-1, 2-benzoquinone and 2, 3-dichloro-1, 4-naphthoquinone react with a series of aryl and alkyl selenolate, generated either by the reaction of Grignard reagents and selenium powder or by the reduction of diselenides with NaBH₄, to give 3, 6-diarylseleno-2, 5-dichloro-1, 4-benzoquinones 3 and 2, 3-diarylseleno-1, 4-naphthoquinones 4 in good yields.     

2-(N-Alkyl-p-hydroxyanilino)-1,4-benzochinone ausp-Benzochinonen und primären aliphatischen Aminen

In acetic (aqueous or chloroform) solutionp-benzoquinones yield with primary aliphatic amines mainly 2-(N-alkyl-p-hydroxy-anilino)-1,4-benzoquinones besides the 2-alkylamino- and 2,5-bis(alkylamino)-quinones. The methyl-, ethyl-,n-propyl-,n-butylhomologues ofp-benzoquinone and the isomer methylderivatives of toluquinone are described. Their structure were established by spectroscopic (UV/VIS, IR, NMR) methods and by synthesis of the methylderivative3 a fromp-benzoquinone andp-hydroxy-N-methylaniline. The influence of other acids on the reaction was studied.

Herrn Prof. Dr.G. Zigeuner, Universität Graz, mit den besten Wünschen zum 60. Geburtstag gewidmet.     

Oxidative transformation of the natural lignan hydroxymatairesinol with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone

The oxidative transformation of the two isomers of the natural lignan hydroxymatairesinol from Norway Spruce (Picea abies) by 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), has been studied. Significant differences in the outcome of the reactions were observed when the pure isomers of hydroxymatairesinol were reacted with DDQ under the same conditions. The different stereoelectronic effects in the two isomers as well as their conformational structures seem to determine the site of reaction, which results in different reaction products. Several products were identified by GC-MS and NMR spectroscopy. Oxomatairesinol was obtained in a yield of 25%.     

Reactions of quinones with some aryl phenols and synthesis of new quinone derivatives

In the present study, the reactions of p-chloranil (1a) and 2,3-dichloro-1,4-naphthoquinone (DCNQ) (1b) with some aryl phenols were investigated. The structures of all compounds were characterized using spectroscopic methods (FT-IR, ¹H NMR, ¹³C NMR, and MS) and microanalysis. The electrochemical behaviors of some benzoquinone and naphthoquinone derivatives have also been investigated in unbuffered aprotic solutions.     

Synthesis and electrochemical properties of substituted para-benzoquinone derivatives

A facile transformation of pentasubstituted tribromophenol derivatives to the corresponding alkyl-substituted dibromo-p-benzoquinones has been achieved using PbO₂ as oxidizing agent in combination with 60% aq HClO₄ in acetone in 70-72% yields. The electrochemical properties of these quinones were studied by means of cyclic voltammetry and compared with p-benzoquinone (BQ) and 2,3-dichloro-5,6-dicyano-benzoquinone (DDQ) recorded under identical experimental conditions.