Naphthoquinone complexes

A very elegant extension of this process to alkyl chlorides, even bearing some functionalities, was developed by Beller using the aheady mentioned well-defined Pd-NHC naphthoquinone complex 11 (Scheme 6.17). The yields are, in general, excellent except when a-substituted alkyl chlorides are employed [76]. 

Douglas, R. A., 1990A, Hydrogen Sulfide Oxidation by Naphthoquinone Complexes—The Hiperion Process, paper presented at the 199th American Chemical Society Meeting. Boston, MA, April. 

Quinones of various degrees of complexity have antibiotic, antimicrobial, and anticancer activities, eg, a2iddinornitosene [80954-63-8] (36), (-)-2-methyl-l,4-naphthoquinone 2,3-epoxide [61840-91 -3] (37), and doxombicin [23214-92-8] (adriamycin) (38) (see Antibiotics Chemotherapeutics, anticancer), ah of these natural and synthetic materials have stimulated extensive research in synthetic chemistry. 

C gives a complex mixture of products that includes naphthoquinone, naphthol denvatives, and benzene denvatives as products of nng degradation [47]... 

The fact that pentacarbonyl carbene complexes react with enynes in a chemo-selective and regiospecific way at the alkyne functionality was successfully applied in the total synthesis of vitamins of the Kj and K2 series [58]. Oxidation of the intermediate tricarbonyl(dihydrovitamin K) chromium complexes with silver oxide afforded the desired naphthoquinone-based vitamin K compounds 65. Compared to customary strategies, the benzannulation reaction proved to be superior as it avoids conditions favouring (E)/(Z)-isomerisation within the allylic side chain. The basic representative vitamin K3 (menadione) 66 was synthesised in a straightforward manner from pentacarbonyl carbene complex 1 and propyne (Scheme 38). 

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... 

Alkylamination of naphthazarin copper complex (37)22 gives predominantly a mixture of 2(or 3),5-bis(alkylamino)-8-hydroxy-l,4-naphthoquinone (38) and 2,6-bis(alkylamino)-4,8-dihydroxy-l, 5-naphthoquinone... 

In the case of the naphthoquinone methine-type near-IR dye 55, reduction with tin(II) chloride under acidic conditions gives the leuco dye 56, which has weak absorption maxima at 350-359nm in methanol. The leuco dye 56 can be isolated as a stable pale yellow compound. The oxidation behavior of 56 has been studied by adding benzoquinone as oxidant in methanol solution. Compound 56 immediately produced new absorption at 760 nm which is consistent with the absorption maximum of 55 (Scheme 19).30 The absorption spectra of the leuco, quinone, and metal complex forms are summarized in Table 3. 

As already shown, domino Michael/ Dieckmann processes are especially useful synthetic procedures with regard to the rapid, efficient assembly of complex organic molecules. This is particularly true for the construction of compounds containing a highly functionalized naphthoquinone or naphthalene unit as central element as found in napyradiomycin A1 (2-125) [54], bioxanthracene (-)-ES-242-4 (2-126) [55], dioxanthin (2-127) [56], and the bioactive compound S-8921 (2-128) [57] (Scheme 2.28). 

Benzocyclobutenedione 57 is transformed to the phthaloylmetal complex 58 by treatment with Fe(CO)5, RhCl(PPh3)3, and CoCl(PPh3)3. The phthaloyliron complex 58 (M=Fe) reacts with alkynes, and subsequent acidification under air then gives the naphthoquinone 59. The cyclization of the phthaloyl-cobalt 58 (M=Co) with alkynes requires AgBF4-activation [32]. (Scheme 22)... 

The reaction of 5-amino-37/-l,3,4-thiadiazole-2-thione 452 with 2,3-dichloro-l,4-naphthoquinone 453 in DMF, at room temperature (rt) for 48 h, gave the complex naphthoquinoimidazolothiadiazole 454 (Equation 104) <1996PS(116)261>. 

For fitting such a set of existing data, a much more reasonable approach has been used (P2). For the naphthalene oxidation system, major reactants and products are symbolized in Table III. In this table, letters in bold type represent species for which data were used in estimating the frequency factors and activation energies contained in the body of the table. Note that the rate equations have been reparameterized (Section III,B) to allow a better estimation of the two parameters. For the first entry of the table, then, a model involving only the first-order decomposition of naphthalene to phthalic anhydride and naphthoquinone was assumed. The parameter estimates obtained by a nonlinear-least-squares fit of these data, are seen to be relatively precise when compared to the standard errors of these estimates, s0. The residual mean square, using these best parameter estimates, is contained in the last column of the table. This quantity should estimate the variance of the experimental error if the model adequately fits the data (Section IV). The remainder of Table III, then, presents similar results for increasingly complex models, each of which entails several first-order decompositions. 

Ethyl (6-Methoxy-l,2-naphthoquinonyl-6) Cyanoacetate. The above naphthoquinone (21.7 g) is added to a solution of 500 cc of ethanol and 14 cc of ethyl cyanoacetate, followed by the addition of 32 cc triethylamine. A deep purple color will develop and the mixture should be swirled for 4 min to dissolve the quinone completely. A solution of 75.9 g of potassium ferricyanide in 320 cc of water is then added to the solution, causing a thick dark complex to form and separate. Redissolve by adding a soluhon of 24 g of sodium carbonate in 1,600 cc of water. Swirl or stir and filter through diatomaceous filter aid. Acidify the filtrate with 100 cc of 6 M sulfuric acid to precipitate 34.8 g of red-orange powder, which is oven dried at 70°. Reciystallize from ethyl acetate to get 19.3 g, mp 157-158.5°. The remaining filtrate is evaporated to a small bulk and reciystallization from ethyl acetate gives an additional 2.8 g of product. 

Most recently, Kiindig has developed some related l,2-di(ferf-amine) catalysts which can be readily prepared from pseudo-enantiomeric quincoridines. These catalysts were shown to be more effective than those disclosed by Oriyama when applied to the ASD of a meso-Caol complex derived from [Cr(CO)3(q -5,8-naphthoquinone)] [188,189],... 

C10H7NO2 1,2-Naphthoquinone 1-oxime (l-NiUoso-2-naphthol) Complexing agent Extiaction-photometiic Gravimetric Separation Transition and rare eartii metals Co, Fe, Mo, U Co U 3... 

C10H7NO2 1,2-Naphthoquinone 2-oxime (2-NiUoso-1 -naphthol) Complexing agent Extiaction-photometric Transition metals Co, Ni, Pd, Ru 3... 

Peroxo Fe(ni), Mn(III) and Ti(IV) porphyrins were reacted with a variety of electron-poor organic substrates in order to compare their activity with that of different metalloper-oxide complexes. Epoxidation of 2-cyclohexen-l-one and 2-methyl-1,4-naphthoquinone was observed, in 25 and 75% yield respectively, with the extremely nucleophilic Fe(III) complex . These results opened new perspectives in the oxidation mechanisms of some enzymatic reactions. 

An interesting effect of Ca2+ ions on the autoxidation of hydroxy-1,4-naphthoquinone, which may have a bactericidal function in sea urchins, has been reported. Autoxidation resulted in the detection of a semiquinone, which was accompanied by only minimal oxygen uptake. The presence of Ca2+ resulted in a massive enhancement in the rate of 02 uptake. Potentiometric titrations revealed that Ca2+ ions, by forming complexes with the compound, lowered the pKa values of its phenolic groups, thereby generating the oxidation-prone phenolate anions. Autoxidation was also facilitated by the spin stabilisation effect of the Ca2+ ions on the naphthosemiquinone.121 This effect may be of importance in mammalian cells, where quinones induce elevations in the free Ca2+ concentration. 

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