Anthraquinones quinizarin

The higher the numerical value of Fm7(Q/Q )> the easier Q is to reduce (more powerful the oxidant). Drugs discussed below include some quinones, such as derivatives of 1,4-benzoquinone or 1,4-naphthoquinone ( °(Q/Q ) = Fm7(Q/Q ) since pK-i == 4.1), and the common cancer therapeutic agent, adriamycin (doxorubicin. Figure 1, 4). The latter structure can be considered to be based on l,4-dihydroxy-9,10-anthraquinone (quinizarin. Figure 1, 5) indolequinones are also of interest (e.g. E09, Figure 1,7). 

Liebermann discovered the reaction between nitrous acid and phenols and secondary amines named after him. He prepared amino-naphthols from nitro-naphthols, synthesised the dihydroxyanthraquinones anthrarufin and chrysazin, and studied the reduction of anthraquinone. Another dihydroxy-anthraquinone, quinizarin, was discovered by F. Grimm by heating hydro-quinone with phthalic anhydride. 

One of tfie most important applications of 4-chloiophenol is in the synthesis of derivatives of quinizarin [81-64-17, anthraquinone dyes (see Dyes,... 

In the benzene and naphthalene series there are few examples of quinone reductions other than that of hydroquinone itself. There are, however, many intermediate reaction sequences in the anthraquinone series that depend on the generation, usually by employing aqueous "hydros" (sodium dithionite) of the so-called leuco compound. The reaction with leuco quinizarin [122308-59-2] is shown because this provides the key route to the important 1,4-diaminoanthtaquinones. 

Dihydroxyanthraquinone. This anthraquinone, also known as quinizarin [81-64-1] (29), is of great importance in manufacturing disperse, acid, and vat dyes. It is manufactured by condensation of phthalic anhydride (27) with 4-chlorophenol [106-48-9] (28) in oleum in the presence of boric acid or boron trifluoride (40,41). Improved processes for reducing waste acid have been reported (42), and yield is around 80% on the basis of 4-chlorophenol. 

In this reaction, three steps, ie, acylation, cyclization, and replacement of the chlorine atom by the hydroxyl group, take place simultaneously in concentrated sulfuric acid. In the course of cyclization 2,7-dichlorofluoran (31) may be formed as a by-product presumably through the carbonium ion (30) ihustrated as follows. The addition of boric acid suppresses this pathway and promotes the regular cyclization to form the anthraquinone stmcture. The stable boric acid ester formed also enables the complete replacement of chlorine atoms by the hydroxyl group. Hydrolysis of the boric acid ester of quinizarin is carried out by heating in dilute sulfuric acid. The purity of quinizarin thus obtained is around 90%. Highly pure product can be obtained by sublimation. 

Quinizarin has been prepared by heating /)-chlorophenol, phthalic anhydride, and sulfuric acid by heating hydroquinone with phthalic anhydride - by heating hydroquinone, phthalic anhydride and c.i>. sulfuric acid by oxidizing anthraquinone... 

Quinizarin (l,4-dihydroxy-9,10-anthraquinone) (9.5), PK2 11.18. Crystd from glacial acetic acid. 

In 1963, Bloom and Hutton suggested5 the structure of leuco quinizarin in solution as 9,10-dihydroxy-2,3-dihydro-l,4-anthraquinone (9a). In 1981, Kikuchi and colleagues6 confirmed the structure by means of H- and... 

It is well known that quinizarin (22) is alkylaminated in air to give a mixture of l-alkylamino-4-hydroxyanthraquinone (23), l,4-bis(alkylamino)-anthraquinone (24), and 2-alkylaminoquinizarin (25) (Scheme 7). The reaction conditions affect the ratio of these products. In a nitrogen atmosphere, or in the presence of sodium dithionite as reducing agent, the main amination product is 24. The solvent effects of the reaction of leuco... 

Although anthraquinone is the starting point for the preparation of many derivatives, involving substitution and replacement reactions, certain compounds are obtained directly by varying the components in the above synthesis. Thus, for example, replacement of benzene with methylbenzene (toluene) leads to the formation of 2-methylanthraquinone. A particularly important variation on the phthalic anhydride route is the synthesis of 1,4-dihydroxyanthraquinone (6.6 quinizarin) using 4-chlorophenol with sulphuric acid and boric acid as catalyst (Scheme 6.3). The absence of aluminium chloride permits hydrolysis of the chloro substituent to take place. 

Nucleophilic displacement of halogen by amines is an important method of introducing amino groups into the anthraquinone ring system. In the Ullmann reaction the displacement is catalysed by metallic copper or by copper ions so that relatively mild conditions can be used. Mechanistic studies suggest that copper(I) ions exert a catalytic effect via complex formation. Derivatives of 1,4-diaminoanthraquinone are of considerable industrial significance. Many compounds are prepared from the reduced form of quinizarin (6.6). 

Concentrated sulphuric acid here performs the same function in the first phase as does aluminium chloride, and by the use of the acid the anthraquinone derivative is obtained in a single operation. The synthesis of quinizarin, described above, provides a preparative illustration of this elegant reaction ... 

The reduction thus extends to the two carbonyl groups in the outer part of the anthraquinone nucleus, but not to the meso carbonyl groups. The picture of the phytochemical reduction is obscured by the fact that anthradiquinone is rather easily decomposed and undergoes autoreduction to quinizarin by partial oxidation and ring cleavage of a second molecule to phthalic acid. 

Blue Anthraquinone Dyes. All the important blue anthraquinone disperse dyes contain at least two amino groups in either the 1,4- or 1,5-positions, often with two additional hydroxy groups in the 5,8- or 4,8-respectively. The 1,4-substituted compounds are obtained by condensing the reduction product of quinizarin, 1,4-dihydroxyan-thraquinone, often called the leuco form, with the desired amines as shown in Figure 2.12. It should be noted that most anthraquinone disperse dyes are mixtures of products and not single compounds as drawn, a fact beneficial to their dyeing performance on polyester. 

Reaction LVIIL (a) Reduction of Phenols and Quinones by Distillation with Zinc Dust. (A., 140, 205.)—When certain aromatic oxygen compounds (phenols, naphthols, quinones, etc.), are heated with zinc dust, they are reduced to the corresponding hydrocarbons. Thus, phenol yields benzene, the naphthols naphthalene while anthracene can be obtained from anthraquinone or its hydroxy derivatives, alizarin, or quinizarin. In this way alizarin was first proved to be an anthracene derivative. (B., 1, 43.) For catalytic reduction of phenols, see C. r. 193, 1023. 

The production of anthraquinone dyes generally proceeds from a few key products generated by electrophilic substitution of unsubstituted anthraquinone or by synthesis of the nucleus. The major methods employed to prepare anthraquinone derivatives substituted in the a-position are sulfonation and nitration. Preparation of b-substituted anthraquinones and of quinizarin (1,4-dihydroxyan-thraquinone) generally is accomplished by synthesis of the nucleus starting from phthalic anhydride and a benzene derivative. 

The formal potentials of adriamycin and quinizarin are almost identical. Therefore, binary monolayers, formed by simultaneous adsorption of both anthraquinones, exhibit only a single voltammetric peak. In these circumstances, traditional elec-troanalytical techniques cannot be used to determine the surface coverages of the individual species. However, as illustrated in Figure 5.29, the large difference in rate constant for the oxidation of the two anthraquinones can be exploited to temporally resolve the charge associated with oxidizing each adsorbate. The only requirement of this approach is that the interfacial kinetics of the individual components should be sufficiently different that two single exponential decays are observed. 

The phenomena occurring with these oxidations were later more accurately investigated by Perlin.3 From anthraquinone in 92% sulphuric acid 90 to 96% dioxyanthraquinones and a small quantity of monoanthraquinones were obtained. Besides a- and / -monooxyanthraquinone, quinizarin, alizarin, and pur-purin could be isolated. If the anthraquinone-sulphuric acid solution is employed as cathode fluid, anthranols, anthrones, and hydroanthranols are formed. If the sulphuric-acid concentration of the anode solution is increased, there are formed sulphurated oxyanthraquinones. 

Quinones, which play an important part in oxidation-reduction processes in nature, have very low solubility in water but their one-electron reduction can be readily investigated in methanol by pulse radiolysis [12], In this way, the semiquinone radicals of 9,10-anthraquinone [12a] and quinizarin [12b], generated by es , CH2OH and CH20 , have been characterized. 

Kortiim and Braun (118) found that a ground-up mixture of silica-gel or AljOs with solid anthracene subjected to ultraviolet irradiation in open air displays very rapidly a new absorption band at 275 m.fi (in diffusely reflected light) and acquires on further exposure a yellow-brown coloration. In similar mixtures with MgO and KCl the photooxygenation of anthracene is much slower, which indicates a specificity of silica gel. It could be spectrally shown that anthraquinone is a primary product giving on further exposure 1,4-dihydroanthraquinone (quinizarine), which could be eluted, producing a red solution with an absorption maximum close to that observed on silica-alumina, as just mentioned above. 

The same strongly colored compounds (quinizarine, chrysazine) have been identified, together with anthraquinone in the final products of insolation of anthracene, adsorbed on active alumina of different previous treatment (119). On zinc oxide only anthraquinone was formed. Naphthalene produced naphthaquinone. 

Sudan II (Sudan Blue, Solvent Blue 35, l,4-bis-(butylamino)-9,10-anthraquinone) [17354-14-2] M 350.5, m 122°, Xmax 604, 652nm, pKj st 9.5 (OH). It is formed from quinizarin (2g see [81-64-1]), 33% EtOH/w-BuNH2 (20ml) and Na2S204 (2g) at 140°/8 hours, evaporate, extract with toluene, chromatograph (AI2O3), the intense blue band in toluene is evaporated, and the residue gave purple needles (Cu lustre) from petroleum ether (b 60-80°) (l.lg, 38%) [Peters Walker JC/zewz Soc 1429 1956, Beilstein 14 IV 460], It forms Cu and Ni salts. 

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