Sulphonyl halides reactions

A few studies are reported which describe the direct oxidation of sulphoxides to sulphonic acids, sulphonyl halides, thiosulphonates and sulphate. These reactions will be considered in this section but it should be noted that they are rarely of synthetic utility. 

An important feature of reactions in solvent mixtures is the effect of substituents in the reactant on the kinetic parameters. As Foon and Hambly (1962) note with reference to the hydrolysis of a series of sulphonyl halides, it is possible to obtain almost any order for the rate constants by selection of the appropriate solvent mixture. The substituent effects also depend on the temperature and, in the case of bimolecular reactions, on the nature of the attacking group, e.g. OH- instead of H20 (Tommila, 1967). 

The reaction with acyl or sulphonyl halides, however, can take two further paths, either ring-contraction to give the isoquinoline A -imide hydrochloride (69) or via dimerization of the short-lived dehydrochlorinated species (68)." ... 

Carboxylic acid anhydrides have been determined via estimation of the water consumed in an analogous reaction but only two examples could be found for a sulphonyl halide, namely p-acetylaminobenzenesulphonyl chloride, where excess water was back-titrated with the Karl Fischer reagent245,246. 

A recent method for determining carboxylic or sulphonyl halides depends on reaction in acetone/water with excess sodium azide. Unconsumed azide is then determined by... 

Sulphonic acids may be made from several different sulphonic acid derivatives. The synthetic utility of these preparative methods is generally limited (perhaps with the exception of the reactions involving sulphonyl halides) since many sulphonic acid derivatives are prepared starting from the sulphonic acid. Some of the more useful procedures are discussed below. 

Sulphonyl halides may be hydrolysed in alkaline or acidic solution, and in boiling water, to give good yields of the parent acid296-303, as shown in equation 60. In addition, a reaction has been reported where a sulphonyl chloride is converted into the corresponding sulphonic acid when the former is dissolved in dimethyl sulphoxide304. The solvent takes part in the reaction as shown in equation 61. 

Sulphonyl halides, most commonly the chlorides, may also be converted into sulphonic acids via a route involving sulphenes. Normally, sulphene is formed by reaction of a sulphonyl chloride, which possesses an a-hydrogen atom, with a tertiary amine as shown in equation 62. There are, however, many other routes by which sulphenes may be formed and these have been reviewed previously305. The intermediate sulphene then reacts with water to give the sulphonic acid. If D20 is used, then a deuterated sulphonic acid is produced306-310, as indicated by equation 63. 

Reaction of sulphonyl halides, that contain an a-hydrogen atom, with tertiary amine bases, under anhydrous conditions, usually occurs via a reactive sulphene intermediate. 

Earlier, it was shown that sulphenes, formed by reaction of sulphonyl halides with a base, reacted with alcohols to give sulphonate esters. These same reactive intermediates have also been used for the formation of sultones, by reaction with carbonyl-containing compounds424-428, as shown in equation 98. If the carbonyl compound contains an a-... 

Sulphonyl halides may be prepared by reaction of some organic compounds with sulphur dioxide in the presence of a halogen or halide ion. Compounds which undergo such reactions include aromatic diazonium salts and some aliphatic species. 

Sulphuryl halides may be used as reagents in the formation of sulphonyl halides from aromatics, alkenes or alkyl halides. The reaction usually proceeds via a radical mechanism, in the presence of a base (which removes HC1 generated in the reaction). If DMF is used as a solvent, yields are often improved534,535. 

Sulphonyl halides are readily prepared by the nitric acid oxidation of sulphenyl halides, which are in turn easily formed by reaction of disulphides with sources of halogens. Thus, alkanesulphenyl chlorides are oxidized to the corresponding sulphonyl chlorides, in high yields301,550-552, as depicted in equation 142. 

Oxidation of sulphides, sulphoxides and sulphones sometimes gives a useful synthetic route to sulphonyl halides. However, it should be noted that such usefulness is relatively rare due to the forcing conditions that are required to break a C—S bond in most instances. Some of the useful reactions are outlined below. 

Sulphones are blessed with high thermal and chemical stability so that oxidation of these species requires extreme, forcing conditions in most cases. However, poly-halogenated sulphones can be oxidized relatively easily to sulphonyl halides and these reactions will be discussed here. 

Sulphonyl halides, other than fluorides, have also been produced by halide exchange. Thus, sulphonyl chlorides may be made from the fluoride by refluxing with aluminium trichloride622,623. Sulphonyl bromides may be prepared from the sulphonyl chloride by reaction with sodium sulphite and base, followed by bromine (equation 158)624... 

Other reactions forming sulphonyl halides from sulphonic acid derivatives include sulphonyl chlorides from esters with PC13647, sulphonyl fluorides from anhydrides with fluoride salts627 and sulphonyl chlorides from trimethylsilyl derivatives of sulphonic acids by reaction with dichloromethyl methyl ether648. 

Sulphonyl halides, attempted reaction with lead thiolate 753 conversion to aromatic thiols 216-220... 

Sulphonyl Halides and Sulphenes.—It is becoming clear that reactions of alkanesulphonyl chlorides in the presence of a tertiary amine are likely to give poor yields of simple sulphonation products, due to the formation of sulphenes (RCHaSOgCl RCH=SOa) and artefacts resulting from them. Electron-withdrawing groups in the substituent facilitate sulphene... 

The most common route to sulphenes, the elimination of hydrogen halide from a sulphonyl halide, has been the subject of a recent mechanistic and kinetic study which led to the conclusion that this reaction most probably proceeds by an El mechanism. Tsuge and Iwanami used this reaction for the generation of benzoylsulphene (130) from benzoylmethane-sulphonyl chloride. The reaction of (130) with a series of anils (131) was found to be somewhat dependent on the presence or absence of triethylamine and very dependent on the nature of R in (131). For R = alkyl, the (4 -I- 2) cycloadduct (132) is the predominant or only product, whereas for R = aryl the (2 + 2) cycloadduct (133) is the reaction product. Similar results were obtained for the reaction of (130) with carbodi-imides. The reaction of (130) with aryl cinnamylideneamines gave Diels-Alder adducts (134). ... 

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