Reductions with Iron

Ditrophenol, -nitropbenol, C H NOj. Colourless needles m.p. 114 C. Prepared as 2-nitrophenol. Reduction with iron and hydrochloric acid gives 4-aminophenol. 

Method B. Reduction with iron and hydrochloric acid. Place 40 ml. of water and 30 g. of grease-free iron filings (1) in a 750 or 1,000-ml. round-bottomed flask, and 25 g. (21 ml.) of nitrobenzene in a small beaker or conical flask. W arm the former on a water bnth at about 60°. Add... 

In a 500 ml. bolt-head flask, provided with a mechanical stirrer, place 70 ml. of oleum (20 per cent. SO3) and heat it in an oil bath to 70°. By means of a separatory funnel, supported so that the stem is just above the surface of the acid, introduce 41 g. (34 ml.) of nitrobenzene slowly and at such a rate that the temperature of the well-stirred mixture does not rise above 100-105°. When all the nitrobenzene has been introduced, continue the heating at 110-115° for 30 minutes. Remove a test portion and add it to the excess of water. If the odour of nitrobenzene is still apparent, add a further 10 ml. of fuming sulphuric acid, and heat at 110-115° for 15 minutes the reaction mixture should then be free from nitrobenzene. Allow the mixture to cool and pour it with good mechanical stirring on to 200 g. of finely-crushed ice contained in a beaker. AU the nitrobenzenesulphonic acid passes into solution if a little sulphone is present, remove this by filtration. Stir the solution mechanically and add 70 g. of sodium chloride in small portions the sodium salt of m-nitro-benzenesulphonic acid separates as a pasty mass. Continue the stirring for about 30 minutes, allow to stand overnight, filter and press the cake well. The latter will retain sufficient acid to render unnecessary the addition of acid in the subsequent reduction with iron. Spread upon filter paper to dry partially. 

Compounds containing two primary amino groups attached to a benzene ring can be prepared by the reduction of dinitro compounds and of nitroanilines, usually with tin or stannous chloride and hydrochloric acid or with iron and very dilute hydrochloric acid. / ara-diamines may also be obtained by the reduction of aromatic amino-azo compounds (e.g., p-aminodimethylanihne from methyl orange, see Section IV,78). p-Phenylenediamine may also be prepared from p-nitroacetanilide reduction with iron and acid yields p-amino-acetaniUde,.which may be hydrolysed to the diamine. 

Naphthaleneamine. 1-Naphthylamine or a-naphth5iamine/7i5 -i2- can be made from 1-nitronaphthalene by reduction with iron—dilute HCl, or by catalytic hydrogenation it is purified by distillation and the content of 2-naphthylamine can be reduced as low as 8—10 ppm. Electroreduction of 1-nitronaphthalene to 1-naphthylamine using titania—titanium composite electrode has been described (43). Photoinduced reduction of 1-nitronaphthalene on semiconductor (eg, anatase) particles produces 1-naphthylamine in 77% yield (44). 1-Naphthylamine/7J4-J2-. can also be prepared by treating 1-naphthol with NH in the presence of a catalyst at elevated temperature. The sanitary working conditions are improved by gas-phase reaction at... 

The Zinin reduction is also usehil for the reduction of aromatic nitro compounds to amines in the laboratory. It requires no special equipment, as is the case with catalytic hydrogenations, and is milder than reductions with iron and acid. Usually ammonium or alkah sulfides, hydrosulftdes or polysulftdes are used as the reactant with methanol or ethanol as the solvent. 

An early synthesis of pyrido[3,4-6]quinoxalines involved cyclization by strong heating of o-aminoanilinopyridinamine derivatives, e.g. (418) to give (419) (49JCS2540). In a related reaction, o-nitroanilinopyridines (420) were cyclized to pyrido-[2,3-6]- or -[3,4-6]-quinoxa-lines (421) by reduction with iron(II) oxalate, probably via a nitrene intermediate (74JCS(P1)1965). 

On reduction, with iron and acetic acid, nitrobenzene yields aniline. 

Persulphate (peroxydisulphate). Persulphate cannot be determined directly by reduction with iron(II) because the reaction is too slow ... 

Reduction with Iron scrap and hydrochloric acid Is preferred because FeClg formed gets hydrolysed to release hydrochloric acid during the reaction. Thus, only a small amount of hydrochloric acid is required to Initiate the reaction. 

Nitro ester 274 undergoes reduction with iron in acetic acid to afford thieno benzoxazepine 275 (Scheme 59 (1994JHC1053)). An alternative route to 275 by the intramolecular formation of a Qhiene 0 bond has been reported (2002JHC163). 

Antimony is obtained from its ores, stibnite, 86283 or tetrahedrite, 3Cu2S 86283. The metal is recovered from high-grade stibnite by reduction with iron ... 

Potassium bromate, KBrOs, is less soluble than the bromide. Thus, most potassium bromate may be removed by filtration. Remaining bromate can be converted to bromide by reduction with iron. After filtering iron from the solution, potassium bromide is obtained by evaporation and crystallizaton. 

Schnur and co-workers " summarized typical reactions that can be performed on functional groups of substituted 2,4-oxazolidinediones without ring opening. These reactions include reduction with iron-acetic acid, chlorosulfonation, nucleophilic displacements of aromatic fluorides, and acid hydrolysis with HCl/formic acid. Nonetheless, there are examples of useful ring cleavage reactions involving 2,4-oxazolidinediones. 

According to a statement of Oldham [53] nitrocellulose can be denitrated by reduction with iron or an iron-zinc mixture in an acetic acid solution. 

Aniline may be made (I) hy Ihe reduction, with iron or tin in HOI, of nitrobenzene, and (2) by the amination of chlorobenzene by healing with ammonia to a high temperature corresponding to a pressure of over 200 atmospheres in the presence of a catalyst (a mixture of cuprous chloride and oxide). Aniline is the end-point of reduction of most mono-nitrogen substituted benzene nuclei, as nitrosobenzene, beta-phenylhydroxylamine. azoxybenzene, azobenzene, hydrazobenzene. Aniline is detected by the violet coloration produced by a small amount of sodium hypochlorite. 

Diaminotoluene has been prepared from 2,4-dinitro-toluene by reduction with iron and acetic acid,2 and by electrolytic reduction 3 from 4-nitro-o-toluidine by reduction with tin and hydrochloric acid 4 and from 2,4-dinitrobenzoyl chloride with tin and hydrochloric acid. ... 

As an alternative to this procedure, the amino group of 160 can be generated from the corresponding nitro derivative prepared from 158 and 159 by reduction with iron. Palladium-mediated cyclization of 160 produced the desired dibenzoxazepine 161 (Scheme 24) <2003JOC644>. Tandem reduction/reductive animation <2004JHC963> and reduction/lactamization <2006JHC1031> procedures were also described. 

The reaction of nitro compound 337 with /-butyloxycarbonic anhydride in the presence of DMAP resulted in 2-nitro-benzenesulfonamide 338, which upon reduction with iron in AcOH gave 339 (Scheme 70). The latter when refluxed with 2,5-dimethoxytetrahydrofuran in AcOH afforded pyrrole sulfonamide 340 in good yield along with the fused 1,2,5-thiadiazepines 103 and 104, as a side product. Subsequently, 340 upon reaction with triphosgene afforded 103 and 104. 

Ethylation of 352 followed by reduction with iron and subsequent hydrolysis afforded the amino acid 355, which underwent intramolecular cyclization catalyzed by iV-(3-dimethylaminopropyl)-./V -ethylcarbodiimide hydrochloride-iV,./V-dimethylaminopyridine complex to give 1,2,5-thiadiazepine 356 (Scheme 73). Similar methodology was employed to obtain the thiadiazepine 357 using (CH3)2C=CCHCH2Br for alkylation <2002JHC81>. 

The former is prepared (Expt 6.15) by the reaction of cyclopentadiene with iron(n) chloride in the presence of diethylamine. Iron(n) chloride is prepared in situ from iron(m) chloride in tetrahydrofuran by reduction with iron metal. This preparation is one of the simplest for ferrocene, although not of general application for substituted ferrocenes. The acetylation of ferrocene in a Friedel-Crafts manner to yield the monoacetyl derivative is described in Expt 6.122. 

Other metal-acid reducing systems may be used reduction with iron and hydrochloric acid is employed on the technical scale for the manufacture of aniline. 

Reduction with iron in hydrochloric acid is one of the most common methods for converting nitroarenes to arylamines. 

Walther obtained the first direct dyes by self-condensation of 4-nitrotoluene-2-sulfonic acid. So-called Sun Yellow is a mixture of different components, depending on the concentration of sodium hydroxide, the temperature, and the duration of the reaction. Oxidation of the intermediate dye and subsequent reduction with iron and hydrochloric acid gives 4,4 diaminostilbene-2,2 -disulfonic acid, which is used for fluorescent whitening agents and azo dyes. The shades are mostly yellow to red. The structure of Direct Yellow 11, 40000 [65150-80-3] (13 is one of the main components) probably contains a mixture of stilbene, azo, and/or azoxy groups. 

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