Anthraquinone 1.8- dihydroxyanthraquinone

Anthraquinone chemistry began in 1868 with the elucidation of the stmcture of the naturally occurring compound alizarin (1) (1,2-dihydroxyanthraquinone) [72-48-0] by C. Graebe and C. Liebermann. 

In 1901, mercury cataly2ed a-sulfonation of anthraquinone was discovered, and this led to the development of the chemistry of a-substituted anthraquinone derivatives (a-amino, a-chloro, a-hydroxy, and a,a -dihydroxyanthraquinones). In the same year R. Bohn discovered indanthrone. Afterward flavanthrone, pyranthrone, and ben2anthrone, etc, were synthesi2ed, and anthraquinone vat dyes such as ben2oylaniinoanthraquinone, anthrimides, and anthrimidocarba2oles were also invented. These anthraquinone derivatives were widely used to dye cotton with excellent fastness, and formed the basis of the anthraquinone vat dye industry. 

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. 

Anthraquinone-a,a -disulfonic acids and Related Compounds. Anthraquinone-a,a -disulfonic acids and their derivatives are important intermediates for manufacturing disperse blue dyes (via 1,5-, or 1,8-dihydroxyanthraquinone, or 1,5-dichloroanthraquinone) and vat dyes (via... 

There is a wide diversity of chemical structures of anthraquinone colorants. Many anthraquinone dyes are found in nature, perhaps the best known being alizarin, 1,2-dihydroxyanthraquinone, the principal constituent of madder (see Chapter 1). These natural anthraquinone dyes are no longer of significant commercial importance. Many of the current commercial range of synthetic anthraquinone dyes are simply substituted derivatives of the anthraquinone system. For example, a number of the most important red and blue disperse dyes for application to polyester fibres are simple non-ionic anthraquinone molecules, containing substituents such as amino, hydroxy and methoxy, and a number of sul-fonated derivatives are commonly used as acid dyes for wool. 

In a related series of 1,2,4-trisubstituted anthraquinone compounds, the effectiveness of various polar and nonpolar substituents to improve on the low heat fastness of 2-amino-1,4-dihydroxyanthraquinone (3.184 R = H) was examined (Table 3.50). Short-chain alkyl groups (methyl, ethyl) and even the pyranylmethyl ether are relatively ineffective but hydroxyalkyl, cyclohexyl, benzyl and morpholinylethyl groups show moderate increases. Further improvement is given by phenyl, pyridylmethyl and morpholinylpropyl. Outstandingly effective, however, are the benzothiazolyl, dodecylphenyl and fluoro-methylphenyl groupings. 

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. 

Anthraquinones. A regioselective synthesis of polyhydroxyanthraquinones is based on Dicls-Alder reactions of I with chloro-substituted naphthoquinones. An example is the synthesis of 1,6-dihydroxyanthraquinone (3) from 3-chlorojuglone (2). Analogous syntheses arc possible by use of vinylogous kctcnc acetals related to I. 

Reaction LXX. Oxidation of certain Hydrocarbons. (B., 14, 1944 A. Spl., 1869, 300 E.P., 1948 (1869).)—This reaction is confined in the aliphatic series almost exclusively to the replacement by hydroxyl of the hydrogen attached to tertiary carbon atoms. A powerful oxidising agent, e.g., chromic acid in glacial acetic acid, is necessary. In the aromatic series the reaction is somewhat more easy to accomplish when the sodium salt of anthraquinone-jS-monosulphonic acid, for example, is fused under pressure with caustic soda and a little potassium chlorate, replacement of both a hydrogen atom and the sulphonic acid group by hydroxyl occurs, and alizarin ( /f-dihydroxyanthraquinone) is obtained. 

Hydroxy- and 1,8-dihydroxy-anthraquinones form neutral 2 1 complexes (209) with divalent metals such as copper and zinc, whilst 1,4- and 1,5-dihydroxyanthraquinones form polymeric complexes (210) and (211), respectively. The latter are virtually insoluble in a wide range of organic solvents and have been used for the mass pigmentation of synthetic polymers. The parent compounds have also found application as mordant dyestuffs, e.g. (212), (213) and (214). 

The ability of the 1-hydroxyanthraquinone system to form chelate complexes is, however, still employed in the synthesis of certain anthraquinone dyestuffs since it permits selective reactions to be carried out. Thus, treatment of the borate ester (215) of 1,2-dihydroxyanthraquinone with acetic anhydride yields l-hydroxy-2-acetoxyanthraquinone, the 1-hydroxy group being protected against electrophilic attack as a result of its being involved in coordination to boron. 

The brilliant red, blue, and turquoise anthraquinone dyes have major industrial significance. The most important red shades are produced by alkyl or aryl ethers of 4-amino-l,3-dihydroxyanthraquinone [81-51-6] (7). 

Anthraquinones The Oj Pile). Alizarin (1,2-dihydroxyanthraquinone) is the orange-red compound of Rubia tinctorum (madder) (Rubiaceae), a longstanding dyestuff in human history. A range of anthraquinones are variously cathartic, antimicrobial and cytotoxic. A variety of anthraquinones are protein kinase inhibitors including alizarin, chrysazin, damnacanthal, emodin and purpurin. 

The molten alkali can have the opposite effect and exert an imdizing action. Thus, it is well known that anthraquinone> -sulfonic acid does not yield hyditRyanthraquinone, but alizarin (l,2>dihydroxyanthraquinone). This reaction can be favored by the addition of an oxidizing agent. 

Alizarin (1,2-dihydroxyanthraquinone) is formed by alkali fusion of sodium anthraquinone-2-sulfonate ( silver salt ). The reaction is rather remarkable in that not only is the sulfo group replaced by hydroxyl, but a second hydroxyl is also introduced. The presence of an oxidizing agent has a favorable effect on the reaction. 

In the source table the compound was named 1,8-Bis(prop-2 -enyloxy)anthraquinone, but it must be 1,4-Bis(prop-2 -enyloxy)anthraquinone as the authors synthesized it from 1,4-Dihydroxyanthraquinone. Figure 1 in the source also shows this 1,4- form. 

Substituted anthraquinones. In the latter figure, 9>5% 2-propanol in carbon dioxide as the mobile phase results in a separation very similar to that with 5.51 2-methoxyethanol in carbon dioxide. In both cases 1,8-dlhydroxyanthraquinone elutes with and right after anthraquinone so those components are not separated, even at much lower modifier concentrations the retention times of anthraquinone and 1,8-dihydroxyanthraquinone increase together with the tailing of the 1,8-dihydroxyanthra-qulnone becoming more and more pronounced as the modifier concentration is decreased. However, with chloroform as the modifier, those two components are significantly split apart, with... 

Danthron, 1,8-Di hydroxv-9, 10-anthracenedione 1,%-dihydroxyanthraquinone chrysazm dantron Allan Amrapurol Diaquone Dorbane Duolax fstin Istizin Modane. C H,04 mol wt 240.20. C 70.00%, H 3.36%, O 26.64%. Prepd from 1,8-anthraquinOne potassium disul-fonate Fierz-David, Blangey, Farbencbemie (Vienna, 5th... 

Further examples of the sulfonation of phenols by this method are the preparation of l,4-dihydroxyanthraquinone-2-sulfonic acid from quinazirin189 and of 1,3,4-trihydroxy-anthraquinone-2-sulfonic acid from purpurin.190... 

Contrary to the naphthazarin case, dihydroxyanthraquinones (QH2) form semi-oxidised quinones which undergo simple bimolecular disproportionation to the diquinone and parent quinone [74]. Both the above reactions have been wrongly given due to printers devil type error m a recent review [12]. The pK for the semi-oxidised anthraquinone derivatives was measured and shown to be around 8. 

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