Acid, sulphinic

Standard methods of synthesis are illustrated for 3-aminopropane-sulphinic acid, starting from homocystamine.  

Allylic oxidation of alkenes by Se02 can be considered to involve the hydrated form of the reagent, SeO(OH)2, or acetoxy-analogues, depending on the reaction media used, prior addition to the alkene via an ene reaction being followed by a [2,3]sigmatropic shift of the allylseleninic acid 

Preparation.—Steady work over recent years has led to the accumulation of a substantial body of information on the factors determining C—S versus C—O 

Matsui and M. Nagano, Chem. and Pharm. Bull. Japan), 1974, 22, 2123. 

Conversions of sulphonyl chlorides into sulphinic acids have been illustrated in the aromatic series, and an interesting aliphatic case (CI2CHSO2CI + EtgN or pyridine - CI3CSO2H, via Cl2C=S02) has been reported.  

The isolation of 3-sulphinopropionic acid from Pseudomonas fluorescens has been reported and the structure confirmed by synthesis involving cleavage of bis(2-carboxyethyl)sulphone. Cleavage of thiiran 1,1-dioxides with metal halides or metal thiolates gives j8-halogeno- and jS-alkylthio-alkane-sulphinates, respectively. 

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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 ... 

Thiophenols (or aryl mercaptans) are obtained by more vigorous reduction of sulphonyl chlorides (or of sulphinic acids), for example with zinc and dilute sulphuric acid, and are isolated by steam distillation ... 

To prepare the free sulphinic acid, dissolve some of the sodium salt in cold water and cautiously acidify with hydrochloric acid avoid an excess of mineral acid since it dissolves the sulphinic acid to a certain extent. The resulting p-tolueneaulphinic acid is difflcult to dry without partial conversion into the sulphonic acid and thiolsulphonic ester... 

Sulphonic acids, sulphinic acids, sulphuric acids, and sul-phonamides... 

The following classes of sulphur compounds occur in Solubility Groups II, III and VII sulphonic acids and derivatives, ArSO,OR sulphinic acids and derivatives, ArSOOR mercaptans, RSH thiophenols, ArSH sulphides or thioethers, RSR disulphides, RSSR sulphoxides, RR S->0 ... 

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 ... 

Aromatic sulphinic acids are oxidised by potassium permanganate.to sulphonio acids and are reduced by zinc and hydrochloric acid to thiophenols. 

XI XI, 1st 1928 1505-1591 Other Acids. Sulphinic acids Benzenesulphinic acid. 

TMSOTf, 111-12.119,122-3,139 p-Toluene-sulphinic acid, 16 Transannular bromodesilyladon, 15 Transmetallation, 10 Tributytin methoxide, 115 Trichlorosilane, 9,10,58 ( )-l-Trichlorosilylhex-l-ene, 9 Tridcca-l,2-dienc, 69... 

Relatively few reports have been published subsequently on the use of these reagents. Hope and coworkers99 have used sodium in liquid ammonia to cleave the benzyl sulphonyl derivatives of cysteamine, L-cysteine and L-homocysteine to prepare the corresponding sulphinic acids, as in equation (42). 

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. 

Several studies confirm an ortho effect leading to a dominating aryl sulphur bond cleavage. For example, the introduction of a bulky ortho substituent17 will provide the formation of the aliphatic sulphinic acid. A series of cyclic sulphones was studied18,19 at the mercury cathode and the results (see Table 2) appear to be fully in agreement with those expected when considering the preliminary works presented above. 

In a set of volumes on sulphur-containing functional groups, the volume on the sulphonium group appeared in 1981 (in two parts). The present volume deals with sulphones and sulphoxides and further volumes, one on derivatives of sulphinic acids and another on derivatives of sulphenic acids, are now in the course of preparation, with a volume on sulphonic acid derivatives planned for the more distant future. 

The Chemistry of Sulphinic Acids, Esters and Derivatives The Chemistry of Sulphenic Acids, Esters and Derivatives... 

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. ... 

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