Sodium sulfide nitro compounds

Zinin Reduction. The method of reducing aromatic nitro compounds with divalent sulfur is known as the Zinin reduction (57). This reaction can be carried out in a basic media using sulfides, polysulfides, or hydrosulfides as the reducing agent. These reactions can be represented as follows when the counter ion is sodium ... 

This compound can be converted to l,5-diamino-4,8-dihydroxyanthraquiaone by reduction of nitro groups with sodium sulfide. 

Tertiary nitro compounds are converted into the cortespooding thiols by the reacdon with sodium sulfide and snlfnr fSj in DMSO followed by the redncdon with Al-Hg. fEq. 7.12. Secondary and primary nitro compounds do not give thiols in these reacdons instead, a complex set of product is formed. 

Another method involves treatment with Lawesson s reagent (see 16-10). When epoxides are substrates, the products are 3-hydroxy thiols. Tertiary nitro compounds give thiols (RNO2 RSH) when treated with sulfur and sodium sulfide, followed by amalgamated aluminum. 

Electrochemically generated nickel is very selective for the reduction of aromatic nitro compounds into anilines, in which alkenyl, alkynyl, halo, cyano, formyl, and benzyloxy groups are not affected.84 Sodium sulfide has been used for the selective reduction of aromatic nitro group in the presence of aliphatic nitro groups (Eq. 6.44).85... 

Let us now consider the conversion of nitro compounds into mercaptanes. Nitro compounds were treated with a mixture of sodium sulfide with sulfur and after that, they were reduced with aluminum amalgam (Kornblum and Widmer 1978) (Scheme 5.8). 

The first stage of the synthesis involves the interaction of a nitro compound with sodium sulfide. When used alone, sodium sulfide is only slightly effective The reactions proceed slowly and the yields of mercaptanes are small. If elemental sulfur is added, the conversion accelerates markedly and the yield increases to 75-80%. The promoting effect of elemental sulfur can be easily explained by the radical-chain mechanism. The reaction starts with one-electron transfer from the nucleophile to the nitro compound further conversions resemble other chain ion-radical substitutions. 

In contrast, reaction of allylic nitro compounds 4 with sodium benzenethiolate in HMPT leads to rearranged allylic sulfides 5.2... 

Sulfur Dyes. These dyes arc synthesized by heating aromatic amines, phenols, or nitro compounds with sulfur or. more usually, alkali polysullides. Sulfur dyes are used for dyeing cellulosic fibers. They are insoluble in water and are reduced to ihe water-soluble leuco form for application to the substrate by using sodium sulfide solulion, The sulfur dye proper is then formed within the fiber pores by atmospheric oxidation. Sulfur dyes constitule an important class of dye lor producing cost-effective tertiary shades, especially black, on cellulosic fibers. 

Iron is not a suitable reducing agent for use when only one of several nitro groups present is to be reduced, or when a nitro compound is to be reduced without altering azo groups which are present. These partial reductions are usually carried out technically with hydrogen sulfide in the form of sodium sulfide (NaaS) or sodium hydrosulfide (NaSH). This reduction method is not limited to partial reductions it frequently finds use in the anthraquinone series for reducing... 

Other reducing agents such as sodium hydrosulfite (sodium dithion-ite, Na,S204) and sodium sulfide have also been used. For example, the latter reduces one of the nitro groups in polynitro compounds selectively 1,3-dinitrobenzene gives 3-nitroaniline in this way (Scheme 7.7). Tin(II) chloride reduces nitro groups selectively in the presence of carbonyl groups under acidic conditions. 

Partial reduction of aromatic polynitro compounds leads to nitro amines. The most successful reagents are the alkali metal or ammonium sulfides in aqueous alcoholIn some instances, sodium bicarbonate combined with sodium sulfide gives better results because of the formation of sodium hydrosulfide, which is believed to be the main reducing agent. Also, aqueous methanol is preferred to aqueous ethanol. Nitro compounds that are sparingly soluble in alcohol solutions may be reduced by hydrogen sulfide in pyridine solution. ... 

The reduction of nitro compounds should initially produce nitroso compounds. This area has not been systematically explored because the nitroso group can be more easily introduced by alternative methods such as direct nitrosation, condensation and oxidative procedures. - In fact, there have been few instances in which nitroso compounds have been isolated as intermediates in reductions of nitro compounds. For example, it was initially believed that w-trifluoromethylnitrobenzene produced the corresponding nitroso compound upon reduction, but subsequently the product was shown to be w-trifluoromethylazox-ybenzene. - Low yields of an intramolecular dimeric, nitroso compound, benzo[c]cinnoline dioxide (1), can be obtained by reducing 2,2 -dinitrobiphenyl with zinc or sodium sulfide (equation I). - ... 

Interest in an old reducing agent, sodium sulfide, was renewed when it was discovered that its reactivity toward nitro groups was sensitive to water. In the absence of water, the aromatic nitro group in (28) can be reduced selectively to (29), without reduction of the aliphatic nitro group, but compounds such as (30), which contain a tertiary aliphatic nitro group eliminate the nitro moiety to yield styrene derivatives (31 Scheme 5). A unique application of the sulfide reduction involves the preparation of isomerically pure substituted aromatic nitro compounds and anilines. ... 

Applications The Karl Fischer reagent can be applied directly to the determination of water in a variety of organic compoimds, including saturated or unsaturated hydrocarbons, alcohols, halides, acids, acid anhydrides, esters, ethers, amines, amides, nitroso and nitro compounds, sulfides, hydroperoxides, and dialkyl peroxides. The use of sodium tartrate dihydrate for standardization of the response of the Karl Fischer reagent has been shown to lead to a small error because of occlusion of about 2% (relative) water in the crystal structure. 

Sodium perborate, NaBOa dlljO (mp 60 °C dec), is used for oxidations of primary aromatic amines to azo compounds [795] or nitro compounds [194] and of sulfides to sulfoxides and sulfones [794]. This reagent does not affect alcohols and only slightly affects alkenes [794]. 

Manufacture of many important amino intermediates used for dyes and other purposes is usually by conversion or replacement of a substituent. For example, as already mentioned, in substituted nitro compounds, the nitro groups may be reduced with iron/hydrochloric acid, hydrogen and catalyst, or zinc in aqueous alkali. Partial reductions can be brought about with sodium sulfide. Amino groups may be introduced by replacing halogens in the aromatic ring. Another approach to amination is by attack on a substituted aromatic compound with ammonia or amines. Thus, for example, direct amination of p-chloronitrobenzene (15a) in the presence of a copper catalyst affords p-nitroaniline (15b) in almost quantitative yield l,4-dichloro-2-nitrobenzene (16) is converted in a similar way to 4-chloro-2-nitroaniline (17). Reactions of ammonia with carboxylic acids or anhydrides are carried out on an industrial scale. 

---