Diquinone derivatives

Two ureido functions introduced into the upper rim of calix[4]arene [52] or the corresponding calix[4]diquinone derivative 41 exhibit good complexa-tion abilities for various anions. Even in highly competitive solvents such as DMSO-d6, quinone 41 shows [53] very strong complexation for H2POj (K4l= 13,900 M-1) or for benzoate (K41=2,430 M-1). The complexation process can be observed using electrochemical methods (cyclic voltammetry) where the addition of anions generates substantial cathodic shifts. 

Triptycene diquinone derivatives, (IV), prepared by Hua (5) were effective in inhibiting nucleic acid or protein syntheses and used in the treatment of multidrug-resistant tumor cells. 

Taking into account om calix[4]tube ligand design10, the novel bis-calix[4]diquinone receptors were prepared via the initial synthesis of various bis-calix[4]arene derivatives connected by alkylene chain units and subsequent oxidation of the remaining phenolic... 

Diquinone isomeric derivatives 71a and 71b can serve as examples of the A—D—A motif [119]. Interestingly, although both derivatives contain weak donors and weak acceptors moieties, they do give segregated stack-... 

The halo quinones (363) undergo photochemical acylation to afford the acyl (364) and the quinol derivatives (365). - The sunlight irradiation of acetic anhydride solutions of the quinone (366) affords the triquinone product (367). Irradiation of (366) in acetone also affords (367) but in addition the diquinone (368) is formed by a free radical path initiated by the abstraction of hydrogen from the amino group by excited state acetone. 

The products from photoreaction of 1,4-naphthoquinone and its methyl and halogeno-derivatives, with xanthene as a hydrogen donor, have been reported.2 A study has been made of the photoreduction of chloranil in acetone in the presence of aromatic hydrocarbons as electron donors,27 and of the photoreduction in ethanol of pentacene-5,7,12,14-diquinone and some derivatives.28 Photoreduction of 3,3, 5,5 -tetramethyldiphenoquinone (17) occurs in benzene, leading... 

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. 

Diquinone Only one lichen compound, pyxiferin, has been identified as a diquinone. If pyxiferin were formed by oxidative coupling of acetate-polymalonate-derived units, the first ring would arise by decarboxylation. 

The synthesis of the three fluorine-containing diphenol is shown in Scheme 10.9. TFPOPH was synthesized by reducing the diquinone compound (2) that were derived from 1,4-benzoquinone with compound (1). The chemical structure of TFPOPH was confirmed by elemental analysis, FTIR, NMR and MS. 

For both (3) and (4) Na+ and Ba + cations form very stable complexes. It is noteworthy that the diamide calix[4]arenediquinone (4) exhibits a larger association constant for Bu NH than for NH4 whereas with the diester derivative (3) the reverse trend is observed. Preliminary electronic absorption titration data of (7) with K+ and Ba + cations gave association constants of 5 x 10" and 3 x 10 respectively. Interestingly, this K+ over Ba " selectivity preference is similar to that exhibited by the dimethyl ether calix[4]diquinone ligand (8) but is the reverse shown by (3) and (4). 

Arene-derived di- and tetraketones presenting the typical quinoid double bond arrangement can be characterized by name suffixes such as. .. quinone,... diquinone etc. the parent name sometimes being subject to certain changes. 

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