Sulphinic acids reactions

One method of preparing sulphlnic acids has already been described (diazo reaction. Section IV,65). Reduction of a sulphonyl chloride with zinc powder and water affords the zinc salt of the sulphinic acid, converted by sodium carbonate to the sodium salt (in which form it is conveniently isolated), and by hydrochloric acid into the somewhat unstable sulphinic acid, for example ... 

Sulphinic acids. Aromatic sulphinic acids are found in Solubility Group II. They may be detected by dissolving in cold concentrated sulphuric acid and adding one drop of phenetole or anisole when a blue colour is produced (Smiles s test), due to the formation of a para-substituted aromatic sulphoxide. Thus the reaction with benzenesulphinic acid is ... 

As has been mentioned in an earlier section, aqueous chlorination of sulphoxides leads to sulphones. If excess reagents are used, sulphonyl chlorides may be formed directly from sulphoxides in good yields (equation 75)89,90,193. In order for this reaction to be synthetically useful, the sulphoxide used should be symmetrical. The product is presumably formed in a stepwise manner via the sulphinyl chloride [RS(0)C1] and the sulphinic acid [RS(0)0H]. In the case of chloromethyl dichloromethyl sulphoxide, the only sulphonyl chloride formed is chloromethanesulphonyl chloride (equation 76) and this may be readily separated from the other products by distillation90,193. Similarly, oxidation of dichloromethyl methyl sulphoxide and methyl trichloromethyl sulphoxide with chlorine in aqueous acetic acid leads to the formation of methanesulphonyl chloride in 75% and 86% yields respectively. Other species are also produced but these are much more volatile and thus easily removed (equations 77 and 78). In the absence of acetic acid the yields are somewhat reduced. 

D. Reaction of Organometallic Compounds with Sulphinic Acid Derivatives 258... 

The first reductive kinetic resolution of racemic sulphoxides was reported by Balenovic and Bregant. They found that L-cysteine reacted with racemic sulphoxides to produce a mixture of L-cystine, sulphide and non-reduced optically active starting sulphoxide (equation 147). Mikojajczyk and Para reported that the reaction of optically active phosphonothioic acid 268 with racemic sulphoxides used in a 1 2 ratio gave the non-reduced optically active sulphoxides, however, with a low optical purity (equation 148). It is interesting to note that a clear relationship was found between the chirality of the reducing P-thioacid 268 and the recovered sulphoxide. Partial asymmetric reduction of racemic sulphoxides also occurs when a complex of LiAlH with chiral alcohols , as well as a mixture of formamidine sulphinic acid with chiral amines, are used as chiral reducing systems. ... 

Backvall and Juntunen and Fuchs and Braish have developed ( )-2-phenylsuphonyl-1,3-dienes prepared under Julia conditions as versatile synthones for a variety of organic transformations103. These dienes undergo facile Diels-Alder reaction and subsequent 1,4-elimination of sulphinic acid by base to generate a new diene (equation 62)103a. An elegant extension of this method is to use chiral sulfinylmaleate which, on Diels-Alder... 

When photolysis (> 290 nm) was carried out in Z-butanol, the identified products were purine, hypoxanthine and purine-6-sulphonic acid. Again, reaction occurred only in the presence of oxygen. The sulphonic acid was thought to arise from the sulphinic acid, but this intermediate could not be detected [150]. 

S-Nitrososulphinates can be made by treating sulphinic acids with N2O4 at about —20 °C in ether (equation 32)76. Use of nitrous acid on alkyl nitrites leads to the formation of the corresponding hydroxylamines (equation 33) in a reaction where it is believed that the first formed nitrososulphinate nitrosates another molecule of the reactant sulphinic acid77. 

The kinetics of the nitrosation of benzenesulphinic acid have been determined79. The reaction is very rapid and requires stopped-flow techniques. This makes benzenesulphinic acid an excellent trap for free nitrous acid, on par with the more well-known hydrazoic acid and hydrazinium ion80. In mildly acid solution reaction occurs via the sulphinic acid molecule and also the sulphinate ion. As expected, the latter is the more reactive and reaction takes place at the diffusion limit. All evidence points to the fact that the first nitrosation by NO+ is the rate-limiting step. 

The same group have used the enzyme combination employed in the aspartate deracemization cited above to deracemize 2-naphthylalanine, hut have made use of an interesting innovation introduced by Helaine et al to pull over the poised equilibrium of the transamination reaction. Cysteine sulphinic acid was used as the amino donor in the transamination. The oxoacid product spontaneously decomposes in to pyruvic acid and SO2 (Scheme 3). 

The direct reaction of [TCO4] in ethanolic solution with dppe and oxalic acid produces the red Tc" complex [Tc(ox)(dppe)2] (552). Attempts to prepare similar complexes with succinic acid, phthalic acid, or salicylic acid failed, or the complexes were stable in solution only. " Similarly, cationic complexes of Tc" are produced by reaction of the versatile precursor [TcO(OH)(dppe)2] (204) with various dithiocarbamates, which produces several complexes of general formula [Tc(dtc)(dppe)2] (553). For this reaction the reductant formamidine sulphinic acid (510) was required in an alkaline solution. The X-ray crystal structure of [Tc(S2CNMe2)(dppe)2] (554) shows a distorted octahedral geometry. Cyclic voltammetry reveals a reversible reduction wave Tc"/Tc couple at —0.53 V, and a reversible oxidation at +0.3 V for the Tc" /Tc" couple. The same compound (554) was also prepared from the thiourea precursor [TcO(tmtu)4] + (91).The reaction of this precursor in dmf in the presence of dppe produced a mixture of brown [TcO(dtc)(tmtu)2] and the Tc" complex (553). The first compound is probably an intermediate... 

Retinol Derivatives. Aryl sulphones have been used in two new syntheses in the vitamin A series. Reaction of /8-cyclocitryl phenyl sulphone (102) with the bromo-compound (103) gives the intermediate sulphone (104), which on base-catalysed elimination affords methyl retinoate (98). Alternatively retinol (99) has been prepared in high yield by condensation of the C15 bromide (105) with the C5 hydroxy-sulphone (106), followed by elimination of sulphinic acid. The syntheses... 

The yields in the Gattermann reaction, however (e.g. o-bromotoluene, Expt 6.74), are usually not as high as those obtained by the Sandmeyer method. Copper powder is also employed in the preparation of sulphinic acids (e.g. benzenesul-phinic acid, Expt 6.75) which are obtained when a solution of a diazonium sulphate is saturated with sulphur dioxide and decomposed by the addition of copper powder. 

These compounds are suggested if sulphur is present. If nitrogen is also present the compound may be an aminosulphonic acid. The infrared spectrum will show absorption at 3400-3200 cm -1 (OH str.) and 1150 and 1050 cm-1 (S=0 str. in a sulphonic add) or at 1090cm-1 (S=0 str. in a sulphinic acid). For derivative preparations for sulphonic acids see Section 9.6.26, p. 1284. The presence of an aromatic sulphinic add may be further confirmed by dissolving in cold concentrated sulphuric add and adding one drop of phenetole or anisole when a blue colour is produced (Smiles s test), due to formation of a para-substituted aromatic sulphoxide. The reaction is ... 

According then to these reactions the formula of the benzene sulphinic acid is exactly analogous to that of benzene sulphonic acid, i.e.,... 

We have then two constitutions for sulphinic acid and its salts, each one of which is proven by definite reactions. 

Some methods of preparing derivatives of the type RHgX haA e already been dealt Avith in describing the reactions of the tyj e R2Hg. In the case of benzene and toluene the mercuration may be carried out directly, using mercuric acetate. If the operation is performed in the presence of alcohol, benzene may be converted to phenylmercuric acetate at 100° C., but the process takes about fifty-five hours to obtain an 80 per cent, yield. When toluene is refluxed Avith mercuric acetate, ortho- and para- ring-substituted compounds are produced. Another method is to treat the aryl sulphinic acids or their sodium salts Avith mercuric chloride, when the folloAving reaction occurs —... 

Methyl-, benzyl- and toluene-sulphonamide react with aromatic diazonium compounds to give isolable triazenes which decompose in the presence of alkali with the formation of the corresponding aromatic azide and the alkyl- or aryl-sulphinic acid salt . This sequence (equation 123), known as the Dutt-Wormall reaction, is mechanisti-... 

SO. REACTION REDUCTION OP A SULPHONCHLORIDE TO A SULPHINIC ACID OR TO A THIOPHENOL... 

Reactivity is not limited to direct addition to the phenoxyl ring structure, and reactions with thiols, amines and olefmic compounds have been reported. Both HOBr and HOCl can elicit oxidation of cysteine residues, where oxidation of the thiol moiety to a sulphinic acid is associated with activation of the latent form of matrix metalloproteinase-7 [111]. Higher doses of HOCl cause inactivation of the enzyme through site-specific modification of tryptophan and the adjacent glycine to yield an unknown product that lacks four mass units [112]. 

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