Sodium hydrosulfite nitroso compounds

The only practical method of preparing 1,4-aminonaphthol is from a-naphthol through an azo dye, the nitroso compound not being readily available. The majority of investigators have reduced technical Orange I with stannous chloride Mi.is.is.ir.is by the procedures discussed above, and benzeneazo-a-naphthol has been reduced by the same reagent. In order to make possible the use of crude, technical a-naphthol a method has been developed for the preparation of the benzeneazo compound, its separation from the isomeric dye coming from the d-naphthol present as well as from any disazo compound by extraction with alkali, and the reduction of the azo compound in alkaline solution with sodium hydrosulfite. The process, however, is tedious and yields an impure product. 

Caution This procedure should be conducted in a good hood. The slurry is stirred while being heated on a steam bath, and solid sodium hydrosulfite is added until the red color of the nitroso compound is completely bleached (Note 5). Then an additional 30 g. of sodium hydrosulfite is added the light tan suspension is stirred with heating for 15 minutes more and is then allowed to cool. The dense diaminouracil bisulfite is filtered from the cooled solution, washed well with water, and partially dried. 

Tertiary and aromatic nitroso compounds are not readily accessible consequently not many reductions have been tried. Nitrosobenzene was converted to azobenzene by lithium aluminum hydride (yield 69%) [592], and o-nitrosobiphenyl to carbazole, probably via a hydroxylamino intermediate, by treatment with triphenylphosphine or triethyl phosphite (yields 69% and 76%, respectively) [298]. Nitrosothymol was transformed to amino-thymol with ammonium sulfide (yield 73-80%) [245], and a-nitroso-/J-naphthol to a-amino-/J-naphthol with sodium hydrosulfite (yield 66-74%) [255]. 

N-Nitroso compounds. Overberger and co-workers found that reduction of N-nilrosodibenzylamine with sodium hydrosulfite is attended with liberation of nitrogen... 

Morel and Sisley (316, 319) suggested that after the nitroso compound is formed it is reduced to an NHj group and then diazotized to the diazo compound. They also found that reduction of a diazonium salt of tyrosine with sodium hydrosulfite resulted in the compound 3-amino tyrosine, instead of the corresponding hydroxy compotmd indicated by Philpot and Small (8). 

Certain nitro compounds in place of reduction to the azo stage under the conditions of the above experiment, form only the light-colored azo y compounds. In some instances the azoxy derivative will be only sparingly soluble in 75 per cent alcohol, and if so may be used as a derivative. Compounds that dissolve in dilute alkali and which possess groups such as nitro, nitroso, azo, etc., are very readily reduced to the corresponding amino compounds by means of sodium hydrosulfite (Na SiO ) in aqueous solution. 

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