Über die Einwirkung von Thionylchlorid auf mehrkernige Polyoxychinone

Waldmann, H.; Ulsperger, E.

doi:10.1002/cber.19500830212

Cited by 8 publications

(3 citation statements)

References 7 publications

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“…1 H NMR (300 MHz, CDCl 3 ): δ 7.05 (s, 2H), 6.79 (s, 2H), 3.87 (s, 6H), 2.46 (s, 6H). 13 Naphthazarin (1): Hydrolysis of 5 (5.48 g, 0.02 mol) in 1 mol/L sodium hydroxide (0.4 L) was performed with stirring at room temperature for 2 h under a nitrogen atmosphere, and acidified with 10% HCl until the color of the reaction solution changed to red, and then extracted with ethyl acetate (40 mL ×2). The organic layer was dried over anhydrous Na 2 SO 4 and concentrated in vacuo.…”

Section: Methodsmentioning

confidence: 99%

A Convenient and Efficient Synthesis of Naphthazarin

Peng

Zhou

Zhang

et al. 2011

Journal of Chemical Research

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A convenient and efficient synthetic method of the important intermediate naphthazarin is presented starting from 1, 4, 5, 8-tetramethoxynaphthalene in an overall yield of 87%. Compared with the reported synthesis, this method has several advantages. Firstly, the reaction conditions are milder; secondly, the workup of each step is simpler and the yield is considerably higher; thirdly, all the reactions involved in the method are more suitable for large-scale preparations.Scheme 1 a, CAN, CH 3 CN, r. t., 98%; b, Zn, Ac 2 O, (Et) 3 N, DMAP, r. t. 91%; c, CAN, CH 3 CN, r. t., 99%; d, 1 mol/L NaOH, 10% HCl, r.t., 98%.

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Section: Methodsmentioning

confidence: 99%

A Convenient and Efficient Synthesis of Naphthazarin

Peng

Zhou

Zhang

et al. 2011

Journal of Chemical Research

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“…A mixture of the hexaacetoxynaphthalene 17 (240 mg) and AICI, (500 mg) was heated a t 160' for 1 h, hydrolyzed with ice and concentrated HCI and allowed to stand for 12 h. The products were separated by chromatography on silica gel using chloroform as eluant. Can A solution of 2,5-dimethylfuran-3,4-dicarboxylic acid dichloride (20) (1 .I g) (19) and p-dimethoxybenzene (0.7 g) in methylene chloride (10 ml) was added dropwise, to a suspension of AICI, (4.5 g) in the same solvent (I5 rnl). After refluxing the mixture for 2 h, hydrolyzing it in the usual way and extracting with chloroform, 1,3- A mixture of 2,5-dimethylfuran-3,4-dicarboxylic acid dichloride (20) (1.1 g) and 1,2-dihydroxy-3,4 dimethoxybenzene (0.9 g) was added in small portions to a molten mixture of AICI, (4.5 g) and NaCl (1.0 g) at 140'.…”

Section: 3-din~ethoxynaphthoqrritrone (11)mentioning

confidence: 99%

“…The cooled melt was hydrolyzed with ice and concentrated HCI, allowed to stand for 24 h and extracted repeatedly with chloroform. The crude extract, when chromatographed on silica gel using a mixture of chloroform a n d methanol (9: 1) as eluant gave 1,3-dimethyl-5,6,7,8-tetrahydroxynaphtho[2,3-clfuran-4,9-quinone (19), m.p. and mixture m.p.…”

Section: 3-din~ethoxynaphthoqrritrone (11)mentioning

confidence: 99%

Friedel–Crafts Condensations with Maleic Anhydrides. III. The Synthesis of Polyhydroxylated Naphthoquinones

Huot¹,

Brassard²

1974

Can. J. Chem.

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The condensation of hydroquinone ethers with an excess of dihalomaleic anhydrides has been found to give particularly good yields of dihalonaphthazarins. The etherification of the latter and the nucleophilic substitution of 2,3-dichloronaphthoquinones have been examined. Finally the structures of the products obtained from the Fries rearrangement of polyacetoxynaphthaIenes have been definitively established.La condensation d'Cthers d'hydroquinones avec un excirs d'anhydrides dihalogCnomalCiques donne des rendements particuliirrement ClevCs en dihalogCnonaphtazarines. La mCthylation de ces substances et la substitution nuclCophile de dichloro-2,3 naphtoquinones ont Ct C Ctudikes. Enfin la structure des produits obtenus lors d e la transposition d e Fries de polyacCtoxynaphtal&nes a CtC Ctablie de f a~o n dCfinitive.Can. J. Chern., 52,838 (1974) Few methods exist for the formation of naphthazarins and none of these are very satisfactory. The syntheses of substituted compounds of this type (whether natural or otherwise), in spite of their apparent simplicity, are therefore usually quite tedious processes. We have attempted to improve the preparation of the basic structure and in principle render its derivatives more readily accessible. The Preparation and Structure of Dihalonaphthazarins and of the Corresponding EthersSince its discovery by Zahn and Ochwat (l), the preparation of naphthazarins by the condensation of hydroquinones (or their ethers) (2) and maleic anhydrides in a molten mixture of aluminum and sodium chlorides has been frequently used. This method remains the most simple way of obtaining many naphthazarins but it suffers the serious inconvenience of giving rather low yields. We have found that the use of excess dichloromaleic anhydride can increase the yield quite spectacularly, in one case to 97%. Stoichiometric amounts of anhydride, dibromomaleic anhydride, and substituted hydroquinones give lower yields. Since the halogens can readily be removed (3), this modification also constitutes a convenient synthesis of some halogen-free naphthazarins.The determination of oxidation-reduction potentials of qninones (4) and the analysis of the n.m.r. spectra of naphthazarins (5) ' have shown that the latter exist mainly in the tautomeric form with the electron-withdrawing groups in the aromatic ring. These results suggest that the predominant tautomer of 2,3-dihalonaphthazarins should be B (Scheme 1). However the n.m.r. spectra of 2a, 2b, and 3 show only one signal at 6 7.33, 7.31, an 7.12, respectively, for ring protons and indicate that these compounds exist mainly with the halogens in the quinoid ring. (The spectrum of 3 could seem ambiguous but is in good agreement with other well established structures such as 6-ethyl-2-hydroxynaphthazarin, F 7.13 (7-CH) (5).) The resonance effects which seem to predominate over other considerations in these cases apparently were not taken into account in earlier works.The etherification of naphthazarins has not been studied extensively. Brass et al. (6) were not abl...

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