Naphthoquinones structure

In a basic medium, structures 2-4 exist. The fluorescence maxima of 1-naphthol shift from 306 (excitation) and 362 nm (emission) in acidic or neutral solution to 338 (excitation) and 462 nm (emission) in base [29]. The increase in wavelength is attributed to the naphthoquinone structures of the ionized forms. These structures are supported by the fact that other stable naphthoquinone compounds exhibit, in neutral solution, almost identical fluorescence spectra as 1-naphthol in basic media. Menadione (2-methyl-1,4-naphthoquinone), for example, has excitation and emission maxima at 335 and 480 nm, respectively, in 95% ethanol [30]. 

Oxidation of the dye during chroming with dichromate creates a naphthoquinone structure in the molecule. Two other important black dyes are C.I. Mordant Black 3, 14640 [3564-14-5] (25, R = H), and C.I. Mordant Black 11 (see Section 3.9.3). 

Ubiquinone (UQ), also known as coenzyme Q, has a benzoquinone structure with a long side chain. The name ubiquinone is for the ubiquitous nature of the quinone. Some bacteria also contain menaquinone (vitamin K2), either in addition to ubiquinone or in place of it. For instance, the reaction center of Rhodopseudomonas viridis contains one ubiquinone and one menaquinone, while in some other bacterial reaction centers both quinones are ubiquinones. Menaquinone has a naphthoquinone structure with a long isoprenoid side chain. The long hydrocarbon side chains in ubiquinone and menaquinone render a high degree of hydrophobicity to these molecules. 

Vitamin K, containing the active 2-methyl-l 4-naphthoquinone structure, exists as Ki in green parts of plants and as K2 in micro-organisms. Deficiency impairs blood coagulation. As with the other vitamins described above, deficiency of the fat-soluble vitamin K most frequently results nowadays when general fat absorption is impaired (see above and Sickinger, 1975). Vitamin K is discussed by Suttie (1978). 

Vitamin Kj, the important dietary factor that is instrumental in maintaining the coagulant properties of blood, contains a 1,4-naphthoquinone structure ... 

The close relationship of Bulgaria and Daldinia with Hypoxylon in the Xylariaceae is illustrated by the occurrence in some Hypoxylon species of perylenequinones and their relatives (Table 22). The structure of hypoxylone (269), the main pigment of the dark purple carpophores of Hypoxylon sclerophaeum collected in French Guyana, followed from analysis of the and C-n.m.r. spectra and comparison with model systems 107). The naphthyl-naphthoquinone structure of hypoxylone suggests oxidative coupling between naphthalene-1,8-diol (258) and naphthalene-1,4,5-triol. 

Vitamin K is a collective name for a group of molecules with the same 2-methyl-1,4-naphthoquinone structure, but with differences in the side chain on position 3 of the naphthoquinone. The number of carbon atoms in this side chain is used to characterize the different molecules. In this nomenclature VKk20) means 20 carbon atoms in the side chain, whereas MK is a synonym for the number of n... 

Naphthoquinone derivatives are also common secondary metabolites of shme molds of the class Myxogastria (formely known as Myxomycota). Examples are the red pigments trichione and homotrichione (9-152) of the sporophores of Trichia floriformis. Naphthalene and naphthoquinone structures are also widespread as red, purple, brown and black pigments in higher... 

A group of natural and synthetic dyestuffs based on the naphthoquinone structure (phenolic) have found use in the formation of lake and other pigments. Naphthoquinones are found in the leaves, blossoms, wood, bark, roots and fruit of about 20 different species. Those which are found in pigment use are AUcannin and Alkannan in AUcanet from plant species such as Alkanna lehmannii Tineo (formerly known as Alkanna tinctoria Tausch.), Macrotomia spp., Onosma spp. and juglone in Walnut qq.v.) fiom Juglans spp. 

Determination of structural features. The ultraviolet spectrum has been of value in the determination of the structure of several vitamins. Thus the presence of an a-naphthoquinone system in vitamin K was first detected by this means. Also the 4-methylthiazole and the 2 5-dimethyl-6-aminopyridine system was first identified in vitamin Bj (thiamine), a- and /3-Ionones can be distinguished since the former contains two conjugated chromophores and the latter three conjugated chromophores. 

The synthetic procedure described is based on that reported earlier for the synthesis on a smaller scale of anthracene, benz[a]anthracene, chrysene, dibenz[a,c]anthracene, and phenanthrene in excellent yields from the corresponding quinones. Although reduction of quinones with HI and phosphorus was described in the older literature, relatively drastic conditions were employed and mixtures of polyhydrogenated derivatives were the principal products. The relatively milder experimental procedure employed herein appears generally applicable to the reduction of both ortho- and para-quinones directly to the fully aromatic polycyclic arenes. The method is apparently inapplicable to quinones having an olefinic bond, such as o-naphthoquinone, since an analogous reaction of the latter provides a product of undetermined structure (unpublished result). As shown previously, phenols and hydro-quinones, implicated as intermediates in the reduction of quinones by HI, can also be smoothly deoxygenated to fully aromatic polycyclic arenes under conditions similar to those described herein. 

In his pioneering work, Sus (1944) assumed that the final product of photodediazoniation of 2,1-diazonaphthoquinone (10.75) is indene-l-carboxylic acid (10.79, not the 3-isomer 10.78). He came to this conclusion on the basis of some analogies (in addition to an elemental analysis). Cope et al. (1956) as well as Yates and Robb (1957) found that the infrared spectrum of the product was consistent with an a,P-unsaturated acid. Later, Melera et al. (1974) verified the structure 10.78 by H NMR spectroscopy. Friedrich and Taggart (1975) showed that the equilibrium between 10.78 and 10.79 at 233 K lies on the side of the latter, but 10.78 clearly predominates at or above 0°C. Ponomareva et al. (1980) showed that not only 2,1-, but also 1,2-diazo-naphthoquinone yields indene-3- and not -1-carboxylic acid. 

Nanaomycin A 103 and deoxyfrenolicin 108 are members of a group of naphthoquinone antibiotics based on the isochroman skeleton. The therapeutic potential of these natural products has attracted considerable attention, and different approaches towards their synthesis have been reported [65,66]. The key step in the total synthesis of racemic nanaomycin A 103 is the chemo-and regioselective benzannulation reaction of carbene complex 101 and allylacety-lene 100 to give allyl-substituted naphthoquinone 102 after oxidative workup in 52% yield [65] (Scheme 47). The allyl functionality is crucial for a subsequent intramolecular alkoxycarbonylation to build up the isochroman structure. However, modest yields and the long sequence required to introduce the... 

Danishefsky et al. succeeded in preparing the benz[a] anthracene core structure 111 of angucycline antibiotics by performing a benzannulation reaction with the cycloalkynone 109 [69]. Deprotonation of the naphthoquinone 110 with DBU yields the desired anthraquinone 111 (Scheme 49). 

Two structures 9a or 9b are possible for leuco quinizarin (9). Bloom and Hutton5 have proposed the structure of 9 to be 9a by comparing the chemical shift of methylene protons with those of leuco naphthazarin (3.05 ppm) and leuco naphthoquinone (3.08 ppm). However, based on UV spectra and chemical reactivity, Egerton and CO-workers7 and Greenhalgh8 independently suggested an equilibrium mixture of 9a and 9b in solution. 

By contrast, alkylamination of naphthazarin (7) in the presence of sodium dithionite followed by oxidation gives l,4-bis(alkylamino)-5,8-naphthoquinone (31).18,19 However, Kikuchi and co-workers20 obtained isomeric l,5-bis(alkylamino)-4,8-naphthoquinone (32) from the reaction of leuco naphthazarin (33) with alkylamine They also isolated 5-alkylamino-leuco-naphthazarin (34) as an intermediate, which is further aminated at the 1-position to give 32. Bloom and Dudek21 have studied the structure of leuco aminonaphthoquinones and their tautomeric equilibria in solution. They concluded that the reaction of leuco naphthazarin (33) or the leuco compound (35) derived from l,5-diamino-4,8-naphthoquinone (36) with methylamine gives mixtures of l,4-bis(methylamino)-31 (R = Me) and 1,5-bis(methylamino)naphthoquinones 32 (R = Me) after oxidation of leuco aminonaphthoquinones (Scheme 10). Some of the structures of leuco aminonaphthoquinones are shown in Scheme ll.20... 

It was found that treatment of a mixture of 120 and 121 with tris(diethylamino-sulfonium) trimethyldifluorosilicate [TASF(Et)] resulted in smooth addition-elimination to the naphthoquinone to form the y-alkylation product 125 (85 %). TASF(Et) is a convenient source of soluble, anhydrous fluoride ion [47]. It is believed that exposure of 121 to TASF(Et) results in fluoride transfer to generate a hypervalent silicate anion, as depicted in structure 124. The transfer of fluoride between TASF(Et) and 121 may be driven by stabilization of the anionic species 124 by delocalization of the carbon-silicon bond into the LUMO of the unsaturated ketone. 1,4-Addition-elimination of this species to the naphthoquinone 120 would then form the observed product. 

The disulfide fragment separating phosphorus and boron atoms was not replaced in 181 by chloral even after refluxing in benzene, evidence for high betaine stability. In methylene chloride, 175 reacts with 1,2-naphthoquinone, yielding phosphorane 182 [Eq. (135)]. This result is surprising, as one could have expected the formation of a betaine structure. 

Diamino-4(3/f)pyrimidinones on reaction with a-diketones give (84JHC1537 85JHC1317) pyrimido[l,2- ][l,2,4]triazines 240. Similarly, the condensation of 2,3-diamino-4(3i/)pyrimidinones with cyclohexandi-one, 1,2-naphthoquinone, acenaphthenequinone, and phenanthraquinone gives the respective condensed pyrimidotriazines of general structure 241 (85JHC1317). 

The lower field 13C NMR signals of 76 suggested a substituted pyridone (5116.3 s, 130.0 s, 138.6 s, 151.4 s and 161.3 s) and a 2-diazo-3-oxo-l,4-benzoquinone (687.5 s, 168.8 s, 172.5 s and 173.6 s) moiety by comparison with the reported values of diaza-quinomycin A and 2-diazo-3-oxo-l,4-naphthoquinone, respectively. Similar stabilities of 1- and 2-diazo-3-oxo-1,4-naphthoquinone under acidic conditions indicated the presence of a diazo group in 76. By combining these results, the structure of 76 was assigned. 

Stenseii, W.G. Jensen, E. Structural De-terminationof 1,4-Naphthoquinones by Mass Spectrometry/Mass Spectrometry. J. Mass Spectrom. 1995, 30, 1126-1132. 

Photolytic. Based on data for phenol, a structurally related compound, an aqueous solution containing 1-naphthoxide ion (3 x 10 M) in room light would be expected to photooxidize to give 2-hydroxy-1,4-naphthoquinone (Tomkiewicz et al., 1971). 1-Naphthol, methyl isocyanate, and other unidentified cholinesterase inhibitors were reported as products formed from the direct photolysis of carbaryl by sunlight (Wolfe et al., 1976). In an aqueous solution at 25 °C, the photolysis half-life of carbaryl by natural sunlight or UV light (X = 313 nm) is 6.6 d (Wolfe et al, 1978a). 

Fig. 10. The structures of 2-methoxy-1,4-naphthoquinone and stigmasta-7,22-diene-3P-ol (spinasterol) with anti-HP activities, isolated from Impatiens balsamina L.

The sample sizes collected by our PMj 5 sampling systems are insufficient to conduct detailed chemical analyses. However, available data for size-fractionated fine particulate matter indicates that PAH quinones, including 1,4-naphthoquinone, 5,12-naphthacenequinone, benz[a]anthracene-7,12-dione, and anthracene-9,10-dione, are important organic components (41, 42). The detection of these molecular species that are similar in structure to semiquinone-type radicals supports the assignment of our EPR signals. 

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