Quinones Naphthoquinones

The term vitamin K2 was applied to 2-methyl-3-difarnesyl-l,4-naphthoquinone, m.p. 54 C, isolated from putrefied fish meal. It now includes a group of related natural compounds ( menaquinones ), differing in the number of isoprene units in the side chain and in their degree of unsaturation. These quinones also appear to be involved in the electron transport chain and oxidative phosphorylation. 

Volatility in steam. Add about 0 1 g. of benzoquinone to 3 ml. of water in a test tube and boil gently. The benzoquinone dissolves to give a yellow solution, which rapidly darkens in colour. Note the irritating and characteristic odour of benzoquinone which has volatilised in the steam. Also given by />-toluquinone and 1,4 naphthoquinone but not by the other quinones mentioned above. 

Reduction, (a) By sulphurous acid. Benzoquinone, /> toluquinone, 1,2-naphthoquinone are readily reduced by SOj ultimately to the dihydroxy-compound. Thus benzoquinone gives colourless hydro-quinone or quinol, />-C2H4fOH)2. 

Benzoquinone ( quinone ) is obtained as the end product of the oxidation of aniline by acid dichromate solution. Industrially, the crude product is reduced with sulphur dioxide to hydroquinone, and the latter is oxidised either with dichromate mixture or in very dilute sulphuric acid solution with sodium chlorate in the presence of a little vanadium pentoxide as catalyst. For the preparation in the laboratory, it is best to oxidise the inexpensive hydroquinone with chromic acid or with sodium chlorate in the presence of vanadium pent-oxide. Naphthalene may be converted into 1 4-naphthoquinone by oxidation with chromic acid. 

Naphthalenediol. This diol can be prepared by the chemical or catalytic reduction of 1,4-naphthoquinone. Both the diol and quinone are of interest because of their relation to the vitamin K family. Carboxylation of 1,4-naphthalenediol with CO2—K2CO2 followed by neutralization gives... 

The cross-conjugated system of two a,P-unsaturated carbonyl groups of both 1,2- and 1,4-quinones occurs in many polynuclear hydrocarbons, eg, 1,2-naphthoquinone [524-42-5] (8) and 1,4-naphthalenedione [130-15-4] (1,4-naphthoquinone) (9) (see Fig. 1). The carbonyl groups may be located in different rings, but occupy positions corresponding to the 1,2- or 1,4-orientation of monocyclic quinones, eg, in naphthalenes such as 2,6-naphthoquinone... 

Quinones of various degrees of complexity have antibiotic, antimicrobial, and anticancer activities, eg, a2iddinornitosene [80954-63-8] (36), (-)-2-methyl-l,4-naphthoquinone 2,3-epoxide [61840-91 -3] (37), and doxombicin [23214-92-8] (adriamycin) (38) (see Antibiotics Chemotherapeutics, anticancer), ah of these natural and synthetic materials have stimulated extensive research in synthetic chemistry. 

Thallium trinitrate oxidi2es naphthols and hydroquinone monoethers, respectively, to quinones and 4,4-diaIkoxycyclohexa-2,5-dienones, eg, 4,4-dimethoxy-2-methyl-2,5-cyclohexadienone [57197-11 -2] (108) (111,112). The yield of (108) is 89%. Because the monoacetal is easily converted to the quinone, the yield of 5-hydroxy-l,4-naphthoquinone [481-39-0] is 64%. 

Quinones and naphthoquinones were explored during the World War 11 Antimalarial Dmg Program. Now that chloroquine resistance is a serious problem, compounds of this group such as menoctone (76) are being reinvestigated. 

Although naphthoquinones represent the largest group of naturally occurring quinones, only a small number of these achieved importance as dyestuffs. 

The synthetic procedure described is based on that reported earlier for the synthesis on a smaller scale of anthracene, benz[a]anthracene, chrysene, dibenz[a,c]anthracene, and phenanthrene in excellent yields from the corresponding quinones. Although reduction of quinones with HI and phosphorus was described in the older literature, relatively drastic conditions were employed and mixtures of polyhydrogenated derivatives were the principal products. The relatively milder experimental procedure employed herein appears generally applicable to the reduction of both ortho- and para-quinones directly to the fully aromatic polycyclic arenes. The method is apparently inapplicable to quinones having an olefinic bond, such as o-naphthoquinone, since an analogous reaction of the latter provides a product of undetermined structure (unpublished result). As shown previously, phenols and hydro-quinones, implicated as intermediates in the reduction of quinones by HI, can also be smoothly deoxygenated to fully aromatic polycyclic arenes under conditions similar to those described herein. 

The only satisfactory method of preparing /3-naphthoquinone is by the oxidation of 1,2-aminonaphthol in acid solution, and the chief problem involved is that of the preparation of this intermediate in suitable yield and purity. This problem and the literature pertaining to it are discussed elsewhere. Most reports of the preparation of the aminonaphthol include some description of its oxidation, but the only particularly helpful comment on the reaction is that ferric chloride is a better oxidizing agent than chromic acid because at a low temperature it docs not attack the quinone, even when present in excess. ... 

One other method is from 1,2-bromonaphthol through the keto-nitrobromide. Though the parent quinone itself is such a sensitive compound that the material so obtained decomposed within a few hours, the method is of considerable value for the preparation of certain substituted -naphthoquinones. ... 

The y-nitrogen atom of a sulfonic acid azide is electrophilic and reacts in an electrophilic aromatic substitution with an activated benzene or naphthalene derivative, e.g., a phenoxide ion, forming a l-tosyl-3-aryltriazene (2.47). The 1,4-quinone diazide is obtained by hydrolysis (Scheme 2-30, Tedder and Webster, 1960). The general applicability of this reaction seems to be doubtful. With 1-naphthol the 1,2-naphthoquinone diazide was obtained, not the 1,4-isomer. 

Naphthoquinone diazides 32, 284ff., see also Quinone diazides 2,3-Naphthotriazole, formation 132 f. Negations, psycholinguistics of 215 Nesmeyanov reactions 273 ff. Nicotinamide-adenine nucleotide (NAD+) 328 f. 

Quinones represent a very large and heterogeneous class of biomolecules. Three major biosynthetic pathways contribute to the formations of various quinones. The aromatic skeletons of quinones can be synthesized by the polyketide pathway and by the shikimate pathway. The isoprenoid pathways are involved in the biosynthesis of the prenyl chain and in the formation of some benzoquinones and naphthoquinones. ... 

The shikimate pathway is the major route in the biosynthesis of ubiquinone, menaquinone, phyloquinone, plastoquinone, and various colored naphthoquinones. The early steps of this process are common with the steps involved in the biosynthesis of phenols, flavonoids, and aromatic amino acids. Shikimic acid is formed in several steps from precursors of carbohydrate metabolism. The key intermediate in quinone biosynthesis via the shikimate pathway is the chorismate. In the case of ubiquinones, the chorismate is converted to para-hydoxybenzoate and then, depending on the organism, the process continues with prenylation, decarboxylation, three hydroxy-lations, and three methylation steps. - ... 

The third pathway involved in the quinones biosynthesis is the isoprenoid route. This pathway is primarily important for the formation of prenyl side chains of prenylquinones (ubiquinone, menaquinone, plastoquinones, etc.). The side chains of ubiquinones and prenylated naphthoquinones derive from polyprenyl diphosphates. 

Reduction of monocyclic aromatic nitro compounds has been demonstrated (a) with reduced sulfur compounds mediated by a naphthoquinone or an iron porphyrin (Schwarzenbach et al. 1990), and (b) by Fe(II) and magnetite produced by the action of the anaerobic bacterium Geobacter metallireducens (Heijman et al. 1993). Quinone-mediated reduction of monocyclic aromatic nitro compounds by the supernatant monocyclic aromatic nitro compounds has been noted (Glaus et al. 1992), and these reactions may be signihcant in determining the fate of aromatic nitro compounds in reducing environments (Dunnivant et al. 1992). 

In the case of the naphthoquinone methine-type near-IR dye 55, reduction with tin(II) chloride under acidic conditions gives the leuco dye 56, which has weak absorption maxima at 350-359nm in methanol. The leuco dye 56 can be isolated as a stable pale yellow compound. The oxidation behavior of 56 has been studied by adding benzoquinone as oxidant in methanol solution. Compound 56 immediately produced new absorption at 760 nm which is consistent with the absorption maximum of 55 (Scheme 19).30 The absorption spectra of the leuco, quinone, and metal complex forms are summarized in Table 3. 

Lillie RD, Pizzolato P, Dessauer HC, et al. Histochemical reactions at tissue arginine sites with alkaline solutions of /J-naphthoquinone-4-sodium sulfonate and other o-quinones and oxidized o-diphenols. J. Histochem. Cytochem. 1971 19 487 197. 

Naphthoquinone is reduced to 1,2,3,4-tetrahydronaphthalene with Et3SiH/TFA in 60% yield.393 Quinones can be reduced to hydroquinones in good yields with hydridosiloxanes such as TMDO with iodide present (Eq. 209).314,316,357 The reductive dehydration of a 1,3-diketone leads to an enone (Eq. 210).374... 

Compounds 4-diazenylbenzosulfonate (13) and 1,2-naphthoquinone were not detected by HPLC under the catalytic conditions. The quinone was not detected because under these conditions 1,2-naphthoquinone is rapidly oxidized into phthalic acid plus two additional products just by H202 without participation of 1. 4-Diazenylbenzosulfonate 13 should be... 

Many quinones (including anthracyclines considered above) are well-known prooxidants that makes them potential DNA damaging agents. It has been shown that menadione (2-methyl-1,4-naphthoquinone), a redox cycling quinone, induced single- and double-strand... 

In the case of ubiquinones we have already considered the ability of quinones to react with superoxide and other free radicals. Naphthoquinones, vitamin K and its derivatives, especially menadione, are the well known producers of superoxide through redox cycling with dioxygen. However, in 1985, Canfield et al. [254] have shown that vitamin K quinone reduced the oxidation of linoleic acid while vitamin K hydroquinone stimulated lipid peroxidation. Surprisingly, later on, conflicting results were reported by Vervoort et al. [255] who found that only hydroquinones of vitamin K and its analogs inhibited microsomal lipid peroxidation. 

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