Naphtho-1,4-quinone formation

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... 

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. 

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. 

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... 

The oxidative formation of the quinone part was used also for the preparation of some benzo[h]naphtho[2,3-d]furan-6,l 1-diones [brasanquinones (137)] (03CB2199,03CB2202 08CB2373 09JCS398 70JIC567) or analogous systems (78CJC517). 

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