Sulphenyl sulphonates

Unsymmetrical thiosulphinates and thiosulphonates are both oxidized by potassium superoxide in pyridine in the presence of 18-crown-6 ether to produce sulphinic and sulphonic acids and a disulphide, under mild conditions (equation 84)200,201. Sulphinic and sulphonic acids were produced from both the R and R substituents whilst the disulphide was derived only from the sulphenyl side of the reactant. Thus, the reaction mixture contained five products, making the reaction not synthetically useful. Pyrolysis of thiosulphinates also produces mixtures of products, one being the thiosulphonate again this is not a synthetically useful reaction202. 

Bridged cations have been indicated as intermediates of the addition of bromine to dialkylacetylenes on the basis of the exclusive trans mode of the reactions. Bridged cations are in each case likely to be formed in the addition of sulphenyl derivatives to alkyl- as well as to arylacetylenes. The retention of trans configuration and the anchimeric assistance effects observed in SNl-type reactions of j8-arylthiovinyl sulphonates indicate that the bridged geometry is always favoured over a linear one. 

Electrophilic Addition.— The use of electrophilic fluorinating agents has been reviewed. A review on organoselenium chemistry includes data on the addition of PhSeBr to steroidal olefins. An improved procedure for chloro-sulphenylation was exemplified by treatment of 5a-cholest-2-ene with thio-phenol and iV-chlorosuccinimide. The resultant adduct (35) was readily converted into the unsaturated aryl sulphone (36). Bromine fluoride is conveniently... 

Adducts of cis-l,4-polybutadiene with benzene- and toluene-4-sulphenyl chlorides can be oxidized quantitatively by 3-chloroperbenzoic acid in a second-stage modification to yield novel sulphone thermoplastics. The fully saturated polymers of structure (3) yielded sulphone products (Scheme 4) with improved thermal stability and higher glass transition temperatures (T, but the oxidation products of partially saturated polymers were very unstable thermally and discoloured on exposure to light. The radical-induced addition of mercaptans... 

Books published recently include several that are wholly devoted to organosulphur compoundsand others " in which specific chapters are relevant to the coverage in this chapter. Reviews have appeared that deal with applications of organosulphur compounds in synthesis " (including uses of yff-keto-sulphides, vinyl sulphones, and vinyl sulphides ) and the synthesis of organosulphur compounds,sulphenyl compounds, indolethiols, allenic sulphides and sulphenamides, organosilyl sulphides, selenides, and tellurides, optically active... 

Preparation.—An important addition to methods for the reduction of sulphonyl compounds to sulphenyl analogues, i.e. the direct reduction of sulphonic acids to thiols using trifluoroacetic anhydride and Bu iN+has been reported. A mixture of thiol and the corresponding trifluorothiolacetate is obtained this, on hydrolysis. 

The conversion of thiols to various sulphenyl derivatives has been utilized as a means of thiol protection as well as, in many cases, a route to disulphides. Sulphenyl derivatives considered in this section include S-sulphonates, sulphenyl iodides, symmetrical and unsymmetrical disulphides (as used for protection) and certain heavy-metal derivatives. A summary of the chemistry of certain sulphenyl derivatives appeared earlier [159]. 

With Acids, Bases. The S-sulphonates appear to be relatively stable in the pH range 1-9 [160] although they are readily decomposed in O.lN-sodium hydroxide. According to Swan, S-sulphonates are relatively stable to N- or 6N-hydrochloric acid and are converted to thiol with hot dilute acid. These studies indicate that S-sulphonates are somewhat more stable than unsymmetrical disulphides and considerably more stable than the sulphenyl iodides or thiocyanates. 

The formation of unsymmetrical disulphides by the reaction of S-sulphonates with thiols is analogous to a number of other sulphenyl derivatives. In general terms the reaction may be represented as shown in eq. 7.14. A number of intermediates in addition to the sulphenyl iodides [92], sulphenyl thiocyanates [108] and sulphenyl sulfonates [175] have been utilized to advantage in the synthesis of unsymmetrical disulphides. These include the monodisulphide dioxides (RSO2—), studied in detail by Field and his colleagues [178], the disulphide monoxides (RSO—) [178, 179] and more recently the S-monothiocar-bonates (ROCS--) [180] and sulphenamides [186]. 

Benzo- and Dibenzo-1,4-dithiins.—An improved synthesis of benzo-l,4-dithiin and -oxathiin is based on a novel intramolecular sulphenylation of the thiol-sulphonates PhY(CHa)2SSOaMe (Y = S or O) in the presence of aluminium chloride. Phenyl-lithium reacts with bromobenzene and carbon disulphide to give 2,3-diphenyl-l,4-benzodithiin via a benzyne intermediate. ... 

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