Reduction sodium dithionate

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... 

Further examples of reductions with sodium dithionate are given in References 220-222. The stereoselective syntheses of 1,3- and 1,4-dienes and pheromones are described in Reference 223. 

Redox titrants (mainly in acetic acid) are bromine, iodine monochloride, chlorine dioxide, iodine (for Karl Fischer reagent based on a methanolic solution of iodine and S02 with pyridine, and the alternatives, methyl-Cellosolve instead of methanol, or sodium acetate instead of pyridine (see pp. 204-205), and other oxidants, mostly compounds of metals of high valency such as potassium permanganate, chromic acid, lead(IV) or mercury(II) acetate or cerium(IV) salts reductants include sodium dithionate, pyrocatechol and oxalic acid, and compounds of metals at low valency such as iron(II) perchlorate, tin(II) chloride, vanadyl acetate, arsenic(IV) or titanium(III) chloride and chromium(II) chloride. 

Reduction of A-arylmaleimides with sodium dithionate gives monomeric and dimeric products a mechanism has been proposed. ... 

There is one report of reductive cleavage of the imidazole ring. Treatment of 122 with sodium dithionate in aqueous ammonia yielded amidine 123, which on hydrolysis with acid gave 124. Compound 124 was obtained directly on reduction with sodium dithionate in aqueous ethanolic sodium bicarbonate (83JHC1003). 

Scheme 6.35 Benzoins obtained from the reduction of benzils in the presence of thiourea derivative rac-36 and sodium dithionate.

Figure 11.8 Self-assembled cyclic-D,L-a-peptide nanotubes containing NDI as the core, (a) Reversible reduction of the NDIs with sodium dithionate. (b) Self-assembly of the peptide NDI nanotube after reduction reaction via chemical or electrochemical methods.

Reduction of 5,7-diaminopyrido[3,4-6]pyrazine with NaBH4 gives the 1,2-dihydro derivative whose enantiomers can be separated by reaction with (K)-1 -(1 -naphthyl)ethylisocyanate <89JMC2089, 89JMC2363). Reduction of the iV-oxides with sodium dithionate gives the deoxygenated product <92S1206>. 

The interaction of the free ligand with cobalt(II) perchlorate in the presence of AgC104 as a precipitant in the nitromethane-methanol mixture made it possible to isolate the [Co(diME l,3pnsar-S6)](C104)3 clathrochelate. The reduction of this clathrochelate with sodium dithionate led to the formation of a cobalt (II) complex that readily produced a free sarcophagine [147],... 

Preparation of iV-methylated pyridinium salts via decarboxylation of N-carbomethoxypyridinium cations was reported (94SC(24)1923). Reduction of pyridinium salts without electron withdrawing groups to give 1,4-dihydropyridines was achieved using sodium dithionate (94TL(35)707). 

Literature procedures were employed in the synthesis of 4-amlno-3-hydroxybenzoic acid 1 (9) and 3-amlno-4-hydroxyphenylace-tic acid (10). The propanoic and propenoic compounds were obtained as outlined in Figure 1. In both Isomeric systems, the intermediate hydroxynitrobenzaldehydes were cleanly converted to the cinnamic acid derivatives by Knoevenagel condensation with malonic acid followed by spontaneous decarboxylation. Reduction of the nitro groups with sodium dithionate then gave the alkene... 

Amino[2- C]uracil (301. accessible from ethyl cyanoacetate and [2- C]urea as previously mentioned, is one of the key intermediates in the Traube-type synthesis of labeled uric acid and xanthine, whose methyl homologues are important biologically active natural products. Nitrosation at C5 with nitrous acid and reduction of the nitroso group with sodium dithionate installed the 5-amino group. Heating of the resulting 5,6-[2- C]diaminouracil (441 in formamide or formic acid resulted in the initial formation of the iV-formamide at C5, which cyclized with elimination of water to afford [2- C]xanthine (451 ". (V-methylation with dimethyl sulfate in basic medium under adequate reaction conditions enabled the separate preparation of [2- C]theobromine ... 

Dithionites. Although the free-dithionous acid, H2S2O4, has never been isolated, the salts of the acid, in particular zinc [7779-86-4] and sodium dithionite [7775-14-6] have been prepared and are widely used as industrial reducing agents. The dithionite salts can be prepared by the reaction of sodium formate with sodium hydroxide and sulfur dioxide or by the reduction of sulfites, bisulfites, and sulfur dioxide with metallic substances such as zinc, iron, or zinc or sodium amalgams, or by electrolytic reduction (147). 

The removal of inorganic salts from reaction mixtures afforded by polymeric materials may be simply and effectively accomplished by dialysis,166 178 after decomposition of remaining periodate with ethylene glycol130 131 or butylene glycol. 161 170 Alternatively, the iodate and periodate ions may be removed as such, or after reduction to free iodine. The iodate and periodate ions have been effectively precipitated by means of sodium carbonate plus manganous sulfate,6 or by lead dithionate,191 barium chloride,24 192 193 strontium hydroxide194 202 or barium hydroxide,203 204 lead... 

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