Anthraquinones hydroxy- from

Tables 7.3 and 7.4 show that unsubstituted and most of the substituted 1-phenoxy-9,10-anthraquinones exhibit photochromic properties. The majority of compounds with mono- and dialkylamino substituents shows no photochromic transformations but undergoes irreversible photochemical conversion.5,8 The photo-chromism is also absent in the case of l-phenoxy-8-hydroxy-anthraquinone. It is suggested31 that, unlike 1-naphthoxyanthraquinone,32 the structural isomer of 1-phenoxy-anthraquinone arises from the rotameric isomer.

As will be seen, only these two mono-hydroxy compounds are possible. Now both of these mono-hydroxy anthraquinones yield alizarin by the introduction of a second hydroxyl group. The only constitution possible for a di-hydroxy anthraquinone obtained from both of these two mono-hydroxy anthraquinones is the 1-2-di-hydroxy compound. As alizarin is thus obtained the two hydroxyl groups in it must be in the 1-2 positions and not in the 2-3 positions. 

Sequential applications of these methods yield naturally occurring anthraquinones, eg, macrosporin [22225-67-8] (86) in 83% yield from 2-chloro-6-methyl-7-hydroxy-l,4-naphthoquinone [76665-67-3] (87), which is produced in 78% yield from (26) (84). 

The kinetics of removal of iron(III) from its complexes with the aminocarboxylate-anthraquinone analytical reagent calcein and with the antitumor anthracycline doxorubicin by l,2-dimethyl-3-hydroxy-4-pyridinone (LI, (251) with R = R = Me) have been monitored. Rate constants for metal removal are almost independent of the concentration of the replacing ligand, indicating dissociative mechanisms they are approximately 1 x 10 s for displacement from doxorubin and between 12 x 10 s and 2 x 10 s from calcein. 

This reaction is specially interesting since many of the above compounds readily yield the corresponding anthraquinone derivatives (see p. 82), e.g., 4-chloro-l-hydroxy-anthraquinone has been obtained from p-chloro-phenol substituted anthraquinones of this type are becoming increasingly important. 

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. 

Aliphatic aldehydes and ketones and also aliphatic-aromatic ketones can be converted into the corresponding hydrocarbons alkyl-phenols can be obtained from phenolic-aldehydes and -ketones p-hydroxy-benzophenone yields p-benzylphenol benzoin and benzil yield dibenzyl anthraquinone yields anthracene dihydride. 

Most of the previously identified 25 chlorinated anthraquinones are found in lichen and fungi (1). The newly discovered examples have a wider range of sources. Studies of the lichen Nephroma laevigatum from the British Columbia coast have identified the new anthraquinone, 7-chloro-l-O-methyl-co-hydroxy-emodin (2157), and the two novel hypericins, 7,7 -dichlorohypericin (2158) and 2,2, 7,7 -tetrachlorohypericin (2159) (1931), as well as 5-chloroemodin (2160), 5-c h I oro -1 - (9 - m e t h v I - o >- h yd ro x ye m od i n (2161), and 5-chloro-co-hydroxyemodin (2162) (1932). In addition to containing several known chlorinated anthraquinones, the Scandinavian fungus Dermocybe sanguinea has afforded the new 5,7-dichloroendocrocin (2163) (1933). The novel tetracyclic anthraquinones... 

Several synthetic compounds containing the naphthoquinone skeleton, such as 2-(4-cyclohexylcyclohexyl)-3-hydroxy- 1,4-naphthoquinone [169], are effective in the treatment of coccidial infection. Two structurally related antibiotics WS-5995A (36) and WS-5995B (37a), isolated from S. auranticolor sp. nov. near Tokyo, efficiently protect Eimeria tenella (a species of coccidia) infection. An inactive component WS-5995C (37b) can be readily converted to the active (36) by simple dehydration [ 170-172]. Compound (36), the structure of which resembles the aforementioned benz[a]anthraquinone antibiotics, is the first example of a 5//-benzo[d ]naphtho[ 2,3-6 ]pyran ring system found in nature. 

Baughman (1992) measured the disappearance rate constants for a number of solvent and disperse azo, anthraquinone, and quinoline dyes in anaerobic sediments. The half-lives ranged from 0.1 to 140 days. Product studies of the azo dyes showed that reduction of the azo linkages and nitro groups resulted in the formation of substituted anilines. The 1,4-diaminoanthraquinone dyes underwent complex reactions thought to involve reduction and replacement of amino with hydroxy groups. Demethylation of methoxyanthraquinone dyes and reduction of anthraquinone dyes to anthrones also was observed. 

Blue and turquoise dyes also play an important role. The most important blue dyes come from ring- or V-substituted derivatives of the two isomers of aminodi-hydroxy-anthraquinone 8 and 9. 

The insensitivity of this reaction towards oxygen makes it very attractive for media where the exclusion of air is not possible, for example, in vivo. As an example, the biologically relevant 4-hydroxy-2-nonenal was released photochemically from an anthraquinone precursor. Interestingly, the phototrigger is reoxidized by molecular oxygen during the reaction (Scheme 13.15) [60]. 

Although 2-hydroxy-5-tcrt-butylazobenzene (29) exists as a true azo compound, annelation of the benzene ring results in 1,2-naphthoquinone 1-phenylhydrazone (35, R = H) and 1,2-naphthoquinone 2-phenylhydrazone (34, R = H) being in a prevailing tautomeric form in compounds derived from 1-naphthol and 2-naphthol. 4-Hydroxyazobenzene (32) and l-hydroxy-4-phenylazonaphthalene (36, R = H) exist in DMSO as true azo compounds. Next step in annelation of the benzene ring in the passive component led to anthracene derivatives. These compounds exist almost completely in hydrazone tautomeric forms (>95%) irrespective of the fact they were formally derived from 1-hydroxyanthraquinone or 2-hydroxyanthraquinone.50 15N chemical shifts show nicely the dramatic changes for compounds 32, 36, (R = H) and 1,4-anthraquinone phenylhydrazone (44). 

The raw materials used to synthesize organic dyes are commonly referred to as dye intermediates. Largely, they are derivatives of aromatic compounds obtained from coal tar mixtures. The majority of these derivatives are benzene, naphthalene, and anthracene based compounds. This section provides an overview of the chemical reactions used to prepare the key intermediates employed in dye synthesis. In this regard, emphasis is placed on halogenated, aminated, hydroxy-lated, sulfonated, and alkylated derivatives of benzene, naphthalene, and anthraquinone. 

Intramolecular Marschalk reaction. Ai. intramolecular Marschalk reaction (9, 376) can be used to effect a synthesis of anthracvclinones from anthraquinones. Thus the oi-hydroxy aldehyde 2, formed on saponification of the a-hydroxydichloride 1, on reduction of the quinone group cyclizes in the alkaline medium to the tetracyclic tran.s- and ci/j-diols(3and4)inaboutequal amounts. Cyclization underphase-transfer conditions results in improved yields and, more importantly, can alter the stereoselectivity. Triton B is the most effective catalyst for stereoselective cyclization to the desired natural tran -diol. 

We wondered if this reaction might be exploited to construct the angularly condensed benzo[a]anthracenes. A problem was the aromatization of the initially formed hydroaromatic ring A under the relatively drastic basic reaction conditions. The starting material 12 was synthesized in a stepwise manner from l-hydroxy-5-methoxy-9,10-anthraquinone [23]. The crucial cyclization can mechanistically be regarded as an intramolecular nucleophilic displacement of the methoxy group to afford a keto ester 13 with about 55% yield (Scheme 5). Only a few nucleophilic additions to electron-deficient anthraquinones are known [20,24,25] and intramolecular reactions of this type are more facile [21, 26-30]. The subsequent ethoxydecarbonylation under acidic conditions to yield ketone 14 presented no problem. 

The remarkable thing is, that while there are ten possible di-brom or di-hydroxy anthraquinones, the particular one necessary was obtained by Graebe and Liebermann. The positions of the two hydroxyl groups were determined by Baeyer and Caro. When alizarin is heated pyro-catechinol, i-2-di-hydroxy benzene, is obtained. Also when pyro-catechinol is heated with ortho- hXhaXic acid and sulphuric acid alizarin results. This last synthesis is analogous to that of anthraquinone from benzene and o //io-phthalic acid (p. 796). 

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