Dinitronaphthalenes, reduction

The first information (37JGU739 67CB2164) about the synthesis of 1,2-dihydrobenzo[crf]indazole by reduction of 1,8-dinitronaphthalene or naphtho[equilibrium with 1,3- and l,5-dihydrobenzo[c[Pg.43]

It was known for long time that the 1,5- and 1,8-dinitronaphthalenes react under the action of concentrated sulphuric acid to yield naphthazarine - a valuable compound for dyeing [30], The mechanism of the formation of this compound (based on experiments of Dimroth and Ruck [18a]) probably consists in the transformation of the nitro compounds to quinone-oximes and the reduction of one of the nitro groups by hydroxylamine split off the oxime ... 

Dinitronaphthalene (62) could be expected to undergo ring closure on reduction, but suitable conditions have not yet been found ... 

Several dinitronaphthalenes have been investigated polarographically [158,159]. The first wave is usually a four-electron reduction. The 1,2- and 1,4-dinitronaphthalenes behave like o and / -dinitrobenzenes, whereas 2,3-dinitronaphthalene does not exhibit a conjugation effect similar to that of (9-dinitrobenzene. Nitro groups in c -positions are reduced in preference to those in y3-positions. 

Dinitronaphthalene could be expected from the coulometric data [110] to undergo ring closure on reduction, but suitable conditions have not been found yet. The diamine [111] and 8-amino-5-hydroxy-l,4-naphthoquinone-1-imine [112] have been reported as products. 

Ward and coworkers have carried out a rather comprehensive study of the reduction of dinitrobenzenes and dinitronaphthalenes with alkali sulfides. They have found that the following general reactions predominate ... 

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