Reduction with sodium hydrosulfite

Anthraquinone Vat Dyes. Many of the best vat dyes are derivatives of anthraquinone or related compounds. A relatively simple dye of this class is Vat Yellow 3, which is made by benzoylation of 1,5-diaminoanthraquinone. It is a yellow pigment that is used as such when properly ground and dried. As a vat dye, it usually is supplied as an aqueous paste. Reduction with sodium hydrosulfite in caustic soda solution gives the alkali-soluble anthra-hydroquinone, which has affinity for cellulosic fibers. After application to the fiber, the insoluble dye is re-formed by oxidation, as described earlier under Vat Dyes. ... 

A number of phthalocyanine derivatives can be made by replacing the hydrogen atoms on the benzene rings. Pigment Green 7, mentioned above, is an example. Vat Blue 29 is a partially sulfonated cobalt phthalocyanine. Reduction with sodium hydrosulfite in caustic soda solution converts it to a soluble form that can be applied to textiles and reoxidized... 

The process of immersion, or vat, dyeing is also employed. Here, dye powders are not water soluble and use special functionalizations, such as oxidation, reduction with sodium hydrosulfite and caustic soda at 50-60 °C, and control of pH to create a water-soluble alkali metal salt promote adhesion [13], Once the dye adheres to the substrate, it subsequently becomes exposed to air, re-oxidizes, and achieves the desired hue. 

When bleaching is requited, a reductive bleach with sodium hydrosulfite and sodium metabisulfite is used. Cotton blends may requite a hydrogen peroxide bleach at pH 9.0—9.5 prior to or iastead of the normal reductive bleach. Chlorine-type bleaches which damage elastomeric fibers are avoided. 

Afterscouring of polyester generally includes a reduction clearing with sodium hydrosulfite and alkaH at 60—80°C to remove any dye remaining on... 

Sodium hydrosulfite or sodium dithionate, Na2S204, under alkaline conditions are powerful reducing agents the oxidation potential is +1.12 V. The reduction of -phenylazobenzenesulfonic acid with sodium hydrosulfite in alkaline solutions is first order with respect to -phenylazobenzenesulfonate ion concentration and one-half order with respect to dithionate ion concentration (135). The SO 2 radical ion is a reaction intermediate for the reduction mechanisms. The reaction equation for this reduction is... 

Although it has been reported (138) that decolorization of wastewater containing reactive azo dyes with sodium hydrosulfite is possible only to a limited extent, others have demonstrated good reduction (decolorization). For example, using zinc hydrosulfite for the decolorization of dyed paper stock (139) resulted in color reduction of 98% for azo direct dyes (139). A Japanese patent (140) describes reducing an azo reactive dye such as Reactive Yellow 3 with sodium hydrosulfite into its respective aromatic amines which ate more readily adsorbable on carbon than the dye itself. This report has been confirmed with azo acid, direct, and reactive dyes (22). 

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. 

Garcia et al. has extended the Batcho-Leimgruber procedure to the synthesis of 2-substituted indoles. Treatment of 36 with o-fluorobenzoyl chloride 37, followed by in situ hydrolysis and deformylation gave ketone 38. Reduction of nitroarylketone 38 with sodium hydrosulfite then furnished indole 39. Similarly, bromoacetylation of 36 gave an acylenamine which was converted into the phthalimido derivative 40. Hydrolysis and deformylation gave phthalimidoketone 41 which underwent reductive cyclization to furnish indole 42. 

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]. 

The reductive cleavage of azo compounds is accomplished in good yields by catalytic hydrogenation [740, 747], with sodium hydrosulfite [255] and with 0,0-dialkyl dithiophosphoric acid (yields 23-93%) [748]. 

Synthesis (Krauli (E. Merck), 1925, Juby et al., 1968, Ehrhart and Ruschig 1972) Thebaine is oxidized with hydrogene peroxide to 14-hydroxycodeinone (Bentley 1954, Hauser 1974), which is hydrogenated directly or via its oxime, or its bromination products to oxycodone. The reduction of 14-hydroxycodeinone can also be carried out with sodium hydrosulfite. Alternatively 14-hydroxycodeinone is prepared by oxidation of codeine. 

Sodium hydrosnlfite has been used to reduce 5-bromo and 5,7-dibromoisatin244 as well as 5-methoxy-l-methylisatin57 to the corresponding dioxindole (65). Reduction of 1-benzylisatin with sodium hydrosulfite led to the dioxindole (65, R = H, R = CH2Ph)111,245 and the isatide (66).245 1,7-Trimethyleneisatin110 underwent a similar... 

Reduction of quaternary salts of aromatic heterocyclic bases occurs much more readily. Quaternary salts of pyridine are reduced preponderantly to 1,2-dihydro derivatives 408 with sodium amalgam and to 1,4-dihydro derivatives409 with sodium hydrosulfite. Potassium... 

Because of this low oxidation-reduction potential, the number of methods available for reducing ferredoxin is limited. Apart from hydrogen gas, ferredoxin may be reduced with organic reductants, such as pyruvate or hypoxanthine in the presence of the appropriate enzymes. Ferredoxin can be reduced nonenzymically with sodium hydrosulfite (dithionite) (Tagawa and Arnon (99) Fry et al. (45)), potassium borohydride (D Eustachio and Hardy (40)), and formamidine sulfinic acid (Shashoua (90)). It can be reduced also by illuminated chloroplasts (Whatley, Tagawa, and Arnon (114)) and, under these conditions, the reduction of ferredoxin is most complete (Bachofen and Arnon (12)). 

An amino group has been introduced at the 5-position of the thiazolidine-dione nucleus by coupling of the reactive methylene group with benzene-diazonium chloride at 0°-5°, followed by reduction of 102 with sodium hydrosulfite [Eq. (31)].142 The tautomeric structural assignment of 102 has... 

The introduction of amino groups into phenols and ethers can be accomplished by the formation and reductive cleavage of their azo compounds. The diazotizing agent may be prepared from sulfanilic acid, and the reduction can be performed with sodium hydrosulfite. Excellent examples are found in the synthesis of l-amino-2-naphthol (85%) and 4-amino-l-naphthol (75%). ... 

This ring closure takes place readily whenever the carbonyl and amino groups occur in the relative positions shown above. Reduction of o-nitro-phenylacetonitrile by stannous chloride produces indole rather than the corresponding amino aldehyde. The synthesis is most useful for the preparation of indole-2-carboxylic acid by reduction of o-nitrophenyl-pyruvic acid with ferrous sulfate and ammonia or with sodium hydrosulfite. The ethyl ester is obtained by a similar reduction with zinc and acetic acid or by catalytic hydrogenation of ethyl o-nitrophenyl-pyruvate over platinum oxide catalyst. ... 

Reduction of 2-hydroxy-3,6-dimethyl-5-phenylazopyrazine (8) with sodium hydrosulfite (dithionite) gave 2-amino-5-hydroxy-3,6-dimethylpyrazine (872), and vigorous reduction of the disodium salt of 2-(p-sulfophenylazo)-3-methyI-5-hydroxypyrazine with stannous chloride and hydrochloric acid gave 2-amino-5-hydroxy-3-methylpyrazine (434). 2-Hydroxy-5,6-diphenyl-3-phenylazopyrazine in methanol was reduced with hydrogen over Raney nickel to 2-amino-3-hydroxy-5,6-... 

Prelab Exercise Write balanced equations for the reduction of Orange II to aminonaphthol with sodium hydrosulfite and for the oxidation of aminonaphthol to 1,2-naphthoquinone using ferric chloride. 

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

Oxycodone. 4,S-Epoxy-14-hydroxy-3-methoxy-17-melhylmorphinan-6-one dihydrohydroxycodeinone 14-hydroxydihydrocodeinone Dihydrone. C,aHaN04 mol wt 315.36. C 68.55%, H 6.71%, N 4.44%, O 20.29%. Prepn by catalytic reduction of hydroxycodeinone, its oxime, or its bromination products or by reduction of hydroxycodeinone with sodium hydrosulfite. Bibliography Small. Lutz,... 

There are several methodologies for the preparation of 3-aminopyridine-2-thione 47a (64JOC2652, 54JCS4516) (Scheme 28), among them the reduction of the corresponding chloro-derivative 54 with sodium hydrosulfite or Fe/CaCl2-... 

The resolution of an a-2,4-dichlorophenoxypropionic acid ester shown in Scheme 2.72 proceeded with very low selectivity when Candida rugosa lipase was used in its native form (E = 1.5). Reductive alkylation of the s-amino groups of lysine residues using pyridoxal phosphate led to only a small improvement. However, when tyrosine residues were nitrated with tetranitromethane, the lipase proved to be highly specific (E = 33). Reduction of the modified nitro-tyrosine lipase with sodium hydrosulfite (which transforms the nitro into an amino group) slightly enhanced the selectivity even further (E = 37). 

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