Aromatics, polycyclic anthraquinones

The Friedel-Crafts reaction, which proceeds via electrophilic aromatic substitution, as illustrated in the following scheme, is unique to the manufacture of anthanthrone pigments. Most other polycyclic anthraquinone pigments are synthesized via nucleophilic ring closure. 

Polycyclic Aromatic Carbonyl Dyes. StmcturaHy, these dyes contain one or more carbonyl groups linked by a quinonoid system. They tend to be relatively large molecules built up from smaller units, typically anthraquinones. Since they are appHed to the substrate (usually cellulose) by a vatting process, the polycycHc aromatic carbonyl dyes are often called the anthraquinonoid vat dyes. 

The use of the stannylquinones 81 results in the regioselective formation of 1,4-naphthoquinones or 9,10-anthraquinones 82 [40]. Highly-oxygenated angularly-fused polycyclic aromatic compounds are prepared by the ring enlargement [41]. (Scheme 29)... 

Various organic molecules are used as photosensitizers in liquid-phase reactions, for example, anthraquinones, aryl ketones, polycyclic aromatic hydrocarbons, dyes, etc. The following mechanism, as the most probable, was suggested for the initiation by the organic photosensitizer Q with the aromatic ring [204-208] ... 

Indigoid Dyes Like the anthraquinone. benzodifuranone. and polycyclic aromatic carbonyl dyes, the indigoid dyes also contain carbonyl groups. They are also vat dyes. 

Quinones of the more reactive, polycyclic, aromatic systems can usually be obtained by direct oxidation, which is best carried out with chromium(vi) compounds under acidic conditions. In this way 1,4-naphthoquinone, 9,10-anthraquinone and 9,10-phenanthraquinone are prepared from naphthalene, anthracene and phenanthrene respectively (Expt 6.128). Also included in this section is the reduction of anthraquinone with tin and acid to give anthrone, probably by the sequence of steps formulated below. 

A variety of plant substances with planar, polycyclic, aromatic structures can intercalate with DNA, examples being the quinoline alkaloid camptothecin and the furanocoumarin phenolic psoralen (Table 12.1). A variety of plant-derived anthraquinones and naphthoquinones bind to DNA and it is notable that the structurally related anthraquinones mitox-antrone and adriamycin are clinically employed as anticancer drugs (Table 12.1). DNA-binding compounds that interfere with DNA repair, DNA replication and gene expression are cytotoxic and have potential as anticancer agents (see Chapter 9). 

The direct synthesis of anthraquinone from phthalic anhydride and benzene has been reported to proceed over zeolite Beta [50] in a shape selective manner. In a conventional anthraquinone synthesis, anthracene is used as a feedstock for oxidation. Once there is a shortage of it in the market, additional anthracene could be produced by isomerization of its isomer, viz. phenanthrene. This, however, is not possible by direct isomerization of the trinuclear aromatic system but involves the partially (symmetrically) hydrogenated species. Consequently, isomerization of symmetrical octahydrophenanthrene to symmetrical octahydro-anthracene was studied by Song and Moffatt [51]. As sketched in Figure 3, a high yield of symmetrical octahydroanthracene can be obtained over zeolite H-mordenite (ngj/nyy = 8) at 250 °C (liquid phase, decalin as solvent). These examples show that (shape selective) catalysis on zeolites is more and more expanding into the conversion of polycyclic aromatics, and we foresee continued interest and success in this field of zeolite catalysis. 

Acetylated cellulose Depending on acetyl content transition from normal phase to reversed phase chromatography Anthraquinones, antioxidants, polycyclic aromatics, carboxyhc acids, nitrophenols, sweeteners... 

A salient feature of anthracene among polycyclic aromatic hydrocarbons is the possibility to prepare a great number of derivatives in different positions some of the derivatives can be obtained from commercially available substituted anthraquinones. This versatility is an advantage for the design of a variety of photoresponsive systems (710 and 16-18). 

The direct bromination of -alkoxylactones at the p position initially generates the a. -unsaturated lactones (eq 14) however, the required radical abstraction is not so facile and further bronii-nation of the Q , -unsaturated lactone proceeds competitively to afford the mono- and dibrominated products. NBS is also used for the oxidative aromatization of polycyclic compounds, including steroids and anthraquinone precursors (eq 15). ... 

Electron transfer is the rate-determined step, and collapse of the intermediate species gives a o-complex. Radical cations of polycyclic aromatic hydrocarbons react with nucleophiles and radicals to yield substituted compounds. The oxidation of anthracene to 9,10-anthraquinone involves the reaction of radical cations with water followed by one-electron transfer and deprotonation ... 

A series of polycyclic p-quinones (9,10-anthraquinones 5,12-naphthacene-quinones 6,13-pentacene diones etc.) display a reversible thermochromic reaction in a reducing medixim, for example, on boiling in dimethylform-amide in the presence of potassium borohydfide. Characteristic colors are formed which disappear on cooling, but reappear on heating (37). Polycyclic quinones with a nonterminal quinoid nucleus give, in acetic acid solution with aromatic amines (especially 3,4-dimethoxyaniline) and on heating, blue... 

Dyes based on anthraquinone and related polycyclic aromatic quinones are of great importance. Many of the most lightfast acid, mordant, disperse, and vat dyes are of this kind. The chromophore is the carbonyl group. 

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