Sodium sulphite, reductions with

As shown in equation 2, the lithium enolate oxidation with O2, followed by sodium sulphite reduction, has been applied with success to oxidation of the enolate derived from 1 the nature of the reducing agent has been decisive for the direct preparation of the hepatoprotective agent Clausenamide (2). As a matter of fact, 2 forms when the treatment with O2 is done in the presence of triethyl phosphite as reducing agent, whereas sodium sulphite reduction affords compound 3. It has been postulated that the transformation 1 —3 occurs through the intermediacy of the peroxide 4. 

It is prepared commercially by treating benzene diazonium chloride with sodium sulphite and then reducing the mixture with zinc dust and ethanoic acid. It can also be prepared by reduction of benzene diazonium chloride with SnCl. ... 

Benzenediazonium chloride reacts in solution with sodium sulphite to give benzenediazonium sodium sulphonate, which when treated with sulphurous acid undergoes reduction to phenylhydrazine sodium sulphonate. The latter readily hydrolyses in the presence of concentrated hydrochloric acid to give... 

Nitrophenylhydrazine may be similarly prepared from p-nitroplienyl-diazonium chloride by reduction with sodium or ammonium sulphite ... 

The carbanions take up 02 and these take up protons to give hydroperoxides in good yields. But because they are explosive in nature, they are not usually isolated and on reduction with sodium sulphite on trialkyl phosphite give alcohols. Alcohols can also be prepared via hydroperoxy molybdenum complexes and alkyl boranes. These reactions are summarized as follows ... 

Amino-l,2,4-triazole was alkylated with 4-nitrobenzyl bromide by simply refluxing the mixture in isopropanol to give SO in excellent yield. The aminotriazole SO was deaminated with NaNOa in aqueous HCI and the nitro group was reduced with ammonium formate catalyzed by 10% Pd/C to deliver 47 in an improved yield over the route shown in Scheme 17. Diazotization of 47, reduction of the diazonium salt with sodium sulphite and Fischer indolization of the resulting hydrazine with 4-( /, /-dimethylamino)butanol dimethyl acetal was performed in a single step to afford rizatriptan (4) in 45% yield. 

This seems to suggest that the sulphur unit is S2. This unit is capable of uniting with hydrogen sulphide to form the trisulphide, H2S3 but sodium sulphite can only combine with one atom of sulphur to yield thiosulphate. The catalytic activity of the hydrogen sulphide would thus appear to be due to its ability to absorb a whole sulphur unit, Sa, and subsequently to give up, on reduction, each atom of sulphur separately, thus ... 

In cold aqueous solution, sodium orthoarsenate reacts with sodium hydrosulphite to form sodium arsenohydrosulphite,6 NagAs(S204)3, a creamy white granular powder. In the presence of sodium sulphite this compound decomposes, forming sodium arsenothiosulphate, an unstable intermediate product, and finally arsenious sulphide.7 If the reduction by sodium hydrosulphite takes place in the presence of hydrochloric acid, some arsenic subsulphide, As3S, is also precipitated,8 and this product is also obtained when the orthoarsenate in aqueous solution is treated with phosphorus trichloride and the mixture saturated with sulphur dioxide.9... 

Notes. (1) The reduction may also be effected with an alkaline solution of sodium sulphite prepared from 8.4 g of sodium metabisulphite and 7.0 g of sodium hydroxide pellets in 90 ml of water. The reaction is probably ... 

General procedure for the reduction of N-chlorosulphonyl /3-lactams with sodium sulphite. A solution of N-chlorosulphonyl /1-lactam dissolved in ether is added slowly to a stirred mixture of about two parts of 25 per cent aqueous sodium sulphite and one part of ether. The aqueous phase is kept slightly basic by addition of 10 per cent potassium hydroxide solution as the reduction proceeds. The reaction course could easily be followed by t.l.c. in which the product has a considerably smaller RF value than the starting material. At the end of the reaction (usually less than 15 minutes) the ether layer is separated and dried and evaporated. The products are of greater than 95 per cent purity as determined by p.m.r. spectroscopy. The reaction may be carried out at 25 °C or at 0°C. 

Isobutyraldehyde is another reagent that has been applied to condensation with amino acids [261 ]. The reaction of methyl ester hydrochlorides of amino acids with isobutyraldehyde and sodium hydrogen sulphite proceeds in a solution of sodium carbonate according to Scheme 5.23. The azomethines produced were chromatographed either as such or as N.-alkyl esters after reduction with zinc powder in methanolic hydrogen chloride. N-Isobutylidene methyl esters of most of amino acids, except His, Arg, Trp,... 

The reagent is sometimes employed by adding sodium sulphite Na2S03 to the acidified solution to be reduced. Some reductions with SO2- are as follows ... 

Physical (including thermochemical and explosive) properties Chemical properties of 2,4,6-trinitrotoluene Reaction with sodium sulphite Oxidation of 2,4,6-trinitrotoluene Reduction of 2,4,6-trinitrotoluene Melhylation of 2,4,6-trinitrotoluene... 

Tlie reduction of vinyl azides with sodium sulphite followed by hydrolysis can lead to ketones [71). 

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