Sulphenyl halides oxidation

The photostimulated reactions of thiolate anions with 2-halo-2 -nitropropane derivatives yield both oc-nitrosulphides via an S l pathway and disulphides (equation 71a)282 284. In contrast with the case of the oxidative dimerisation products of the mono-enolates, the disulphides are formed via an ionic mechanism nucleophilic attack by the thiolate anion on the a-halogen and subsequent reaction of a second thiolate with the sulphenyl halide. As expected for such a process, disulphide formation is favoured (and thus a-nitrosulphide formation is disfavoured) the more nucleophilic the thiolate (i.e. derived from a less acidic thiol) and the easier the abstraction of the halo-substituent (i.e. I > Br > Cl). Use of the protic solvent methanol instead of the usual dipolar aprotic solvents for the reaction of equation 71a is detrimental to the yield of the S l substitution products exclusively disulphides are formed285 (equation 71b). Methanol solvation probably retards the dissociation of the radical anion intermediate in the SRN reaction, into radical and anion, and hence retards the chain reaction relative to the ionic reaction. The non-nucleophilic methylsulphinate ion gives only an S l reaction product with 2-bromo-2-nitropropane286. 

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. 

A general synthesis of 2-substituted l,2-benzisothiazolin-3-ones from 2-mer-captobenzoic acid involves esterification, halogenation to the sulphenyl halide, conversion into the sulphenamide, and cyclization with a strong base. The synthesis of 3-oxo-3/f-l,2-benzisothiazole 1-oxides by the action of hydrazoic acid on 2-sulphinylbenzoic acids has been extended (see Vol. 2, p. 579). 2-SuI-phinylbenzamides (48) react with hydrazoic acid in polyphosphoric acid to give 3-imino-3//-l,2-benzisothiazole 1-oxides (49) together with the related 5 functional derivatives of (49), and an unusual alkaline ring-scission to (50), were also described. ... 

Several papers report on the nucleophilic reactivity of dithiocarbamate ions towards alkyl halides, 1,2-dibromoalkyl compounds, alkyl and aryl chloroformates, chloroacetic acid, chloroacetates, 3-halo-genophthalides, sulphenyl chlorides, sultones, and trialkylam-monium compounds. Examples of a similar reactivity of dithiocarbazate anions have also appeared. " A series of papers deal with addition or addition-elimination reactions of dithiocarbamate - or dithiocarbazate anions with w-nitrostyrene, 2-thioxo-, 2-oxo-, and 2-imino-5-methoxycarbonylmethylidene-4-thiazolidones, dimethyl acetylenedicar-boxylate, and NN -dialkyl phenylpropiolamidines. S-Monoalkylated N-cyanodithioimidocarbonates (492) underwent oxidative ring-closure to give 3-halogeno-l,2,4-thiadiazole sulphides (493) on treatment with halogenating agents. ... 

---