Naphtho-1,4-quinones, from

C 4H s04, Mr 272.30, black-violet prisms, mp. 264-266°C, [a]g -p365 (CH3OH). An o- naphtho-quinone from the mycosymbiont of the lichen Trype-thelium eluteriae. 

C Red No. 2) has been utilised by Hill2 and by Bufton and Saddlerl42 to assay neomycin in aqueous solution. Amaranth may also be used to determine neomycin in production samples from fermentation-recoveryl68. The dye, Orange II, has been similarly described(A max. = 484 nm). Complex formation between neomycin and the dye is very dependant on the ionic strength of the solution, thus necessitating careful control of reaction conditions to ensure complete precipitation of the complex during the assay procedure. Reaction of sodium 1,2-naphtho-quinone-4-sulphonate with... 

In a similar manner, benzo[a]phenazine 7,12-dioxide derivatives are formed from 1,4-naphtho-quinones in dimethylformamide. " ... 

Synthetically, compound 152 was prepared by the Friedel-Crafts procedure from furan-3,4-dicarbonyl chloride and a tetralin derivative (85JCR (S)338). 1,4-Dihydro-l,4-epoxy-5,8-naphthoquinone, when treated with 3,6-di(2-pyridyl)-l,2,4,5-tetrazine, yielded the quinone 153 (75JCS(P1)1339) derivatives of 153 are also known (74CC1034). The parent compound (153) is a stable derivative of the unstable isobenzofuran. Finally, 3-acetyl-2-furyl-1,4-benzo- (or -naphtho-) quinones are isomerized photochemically in aprotic solvents into the quionones 154 (66HCA1806). 

Only a few oxazoloquinones are known. 2-Methylnaphtho[2,3-d]oxazole-4,9-dione (207) was obtained from 2-acylamino-3-alkylamino-l,4-naphtho-quinone in the presence of concentrated sulfuric acid (69T2427). Similarly, derivatives of 208 were obtained from 2,5-bis(acetylamino)-3,6-dihydroxy-1,4-benzoquinones and acyl halide or anhydride (64ZOB3037). The five-membered ring is easily cleaved in warm dilute acid or base (64ZOB3037). 

The dried roots of Salvia miltiorrhiza form the Chinese drug tan-shen , from which a number of furanonaphthoquinones-the tanshinones, isotanshinones, and cryptotanshinones-have been isolated. The roots also contain an o-naphtho-quinone, miltirone, whose structure (34) was assigned on the basis of its spectral properties and the formation of a triacetate which on hydrolysis and oxidation gave a hydroxy-1,4-naphthoquinone. 

Vitamin K activity is associated with at least two distinct natural substances, designated as vitamin K, and vitamin Kj. Vitamin K or phylloquinone (phytonadione) is 2-methyl-3-phytyl-l,4-naphthoquinone it is found in plants and is the only natural vitamin K available for therapeutic use. Vitamin K is actually a series of compounds (the mena-quinones) in which the phytyl side chain of phylloquinone has been replaced by a side chain built up of 2 to 13 prenyl units. Considerable synthesis of menaquinones occurs in Gram-positive bacteria indeed, intestinal flora synthesize the large amounts of vitamin K contained in human and animal feces. In animals menaquinone-4 can be synthesized from the vitamin precursor menadione (2-methyl-l,4-naphtho-quinone), or vitamin Kj. Depending on the bioassay system used, menadione is at least as active on a molar basis as phylloquinone. 

The betaine 24, obtained from the reaction of 2,3-dichloro-l,4-naphtho-quinone with a pyridine/water mixture, reacts with CI2 to form A -(l-... 

All well-characterized photosynthetic reaction centers contain quinone molecules. Type II reaction centers, such as Photosystem II (PS II), contain two quinones, one that functions as a bound one-electron acceptor, and the other that functions as a mobile two-electron (and two-proton) accumulator. In PS II, plastoquinone-9 (PQ-9) serves the role of the mobile quinone, which shuttles electrons to Photosystem 1 (PS 1) via the cytochrome hjj/complex. Type 1 reaction centers, such as PS I of cyanobacteria and green plants, contain two bound phylloquinones (PhQ — vitamin Kj, 2-methyl-3-phytyl-l,4-naphtho-quinone). One or both PhQ molecules function as one-electron acceptor, shuttHng electrons from the primary acceptor A (a chlorophyll a monomer), to (a [4Fe-4S] cluster). PhQ neither becomes protonated as part of the electron transfer process nor diffuses from the PS I complex as part of its normal function. The drop in Gibbs free energy from A to is estimated to be ca. 250 mV to 320 mV. > Thus, PhQ plays an important role as an intermediate in the early stages of electron transfer in PS I. ... 

Condensed benzo[i>]furan molecules can be prepared by inter- or intra-molecular Diels-Alder reactions from furo[3,4-b]benzofurans, and some interesting intermolecular examples are listed below. As can be seen, the furo[3,4-i>]benzofuran 60 underegoes Diels-Alder reactions with naphtho-l,4-quinone in the presence of Znl2 as a Lewis acid to form the aromatized cycloadduct. When the diene precursor reacts with benzo-l,4-quinone in the absence of Znl2, the product is obtained as an endo-exo mixture <00JCS(P1)1387>. 

Benzofuroxans can be prepared by oxidation of o-quinone dioximes with, for example, fer-ricyanide or hypohalite in a process which closely parallels the formation of monocychc furoxans from glyoximes. Its utility is restricted by the availability of the starting materials which are themselves often best made by reduction of the furoxan. However, it is a valuable approach when the parent quinone or its monooxime is accessible by other means. It was, for example, the route originally used for naphtho[l,2-c]furoxan, the first aromatic-fused derivative <1886CB176>, and it is the method of choice for acenaphthofuroxans (11). In other cases oxidation of o-nitroanilines or thermolysis of o-nitroaryl azides are more suitable. 

Positive Photoresists. Positive resists are entirely different from negative resists. For the purposes of this discussion we restrict ourselves to visible-light-sensitive materials. Typically, these materials are mixtures of low-molecular-weight phenol-formaldehyde polymers and derivatives of naphtho-1,2-quinone diazide, the photosensitive component. The former is soluble in aqueous alkali, but the presence of the latter, a hydrophobic species, inhibits attack of this developer on the film. On irradiation the "sensitizer" is converted to a ketene, which, after reaction with water, forms a base-soluble carboxylic acid. Thus the irradiated part of the film is rendered soluble in the developer and it can be removed selectively. The important feature of this system is that the unirradiated areas are not swollen by the developer and the resolution of this material is quite high. It is possible to prepare gratings having several... 

A similar domino sequence in an intramolecular Diels-Alder version of the previous example provided access to pyrano benzo-[60] and naphtho-[61] quinones as shown in Scheme 25. Depending on substitution patterns of the aldehyde 111, para-(112 and 116) or ortho- H3 and 117) adducts or both were obtained. Typically high diastereoselectivity was observed. Libraries 114 and 115 were tested for their ability to reverse the multidrug resistance phenotype resulting from overexpression of drug efflux pumps. The compounds were evaluated in mammalian... 

Anthra-9,10-quinone is the eventual product from the cycloaddition of buta-1,3-diene to naphtho-l,4-quinone after oxidation of the tetrahy-droanthraquinone adduct. 

Further details have appeared of the one jx)t synthesis of naphtho[2,l-g]quinoline-7,12-dione derivatives (250) from irradiation of the quinolinedione (251a) in the presence of l,l-diarylethylenes. The same workers have more fully described their earlier findings on the formation of (252) and thence (253) from the photoinduced reaction of dichloronaphtho-1,4-quinone (251b) and the ethylenes. In this latter system, CIDNP studies have... 

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