Sulfenyl derivatives

Reactions and reactivity of nucleophiles with thiolsulfonates 137 Nucleophilic substitutions of sulfenyl derivatives general considerations 139 Bimolecular substitution at sulfenyl sulfur stepwise or concerted 140 Reversibility in reactions of nucleophiles with cyclic thiolsulfonates 145 Other reactions of thiolsulfonates 147... 

Sulfenic acids exhibit high nucleophilic reactivity toward sulfenyl derivatives RS—X possessing a readily displaced group X (Kice and Cleveland, 1973a). The product of such a reaction is a thiolsulfinate as shown in (11). Analysis of appropriate kinetic data (Kice and Cleveland, 1973a) shows that, when R = Ph and —X = —Cl, —Br, or —S(n-Bu)2, Jt, is from 4 x 104 to 4 x 105 times faster... 

The reactions of thiosulfonates shown in general form in (167), and which constitute the majority of their chemistry, are, of course, substitution reactions at a dico-ordinate, or sulfenyl, sulfur. Substitutions of this type occur widely and with great frequency in the chemistry of all types of sulfenyl compounds. Because of their extreme importance in the chemistry of both thiolsulfonates and other sulfenyl derivatives, it is appropriate that we now review some of the major features regarding their mechanism that have emerged from the study of such reactions with various sulfenyl derivatives. 

X in PhjCSX on the rate of reaction (174) of the sulfenyl derivatives with either n-butylamine or hydroxide ion. Their results are in Table 9. The order of... 

Sulfenyl chlorides and most of the other sulfenyl derivatives react with alkenes to give generally anti addition products with a high stereoselectivity. Although the mechanism of these reactions is still under study, it is usually accepted that sulfenyl transfer from the carrier to nucleophilic double bonds is consistent with the multistep mechanism reported in equation 907b. 

Simple 1,2-additions to this compound have been observed123131132 also in other sulfenylation reactions, and in other electrophilic additions involving strongly bridged intermediates. Although these results have been interpreted as evidence that additions of sulfenyl halides to symmetrical alkenes do not involve open carbenium ions before the product-determining step, the different behavior observed in the case of 49 suggests123 that close proximity is necessary to have transannular participation of 7r-bonds, at least in additions of sulfenyl derivatives and of some other electrophiles carried out in the presence of efficient nucleophiles. 

Areneselenenyl halides react with double bonds similarly to sulfenyl derivatives 1,2-additions are generally anti stereospecific, in agreement with the involvement of a bridged intermediate [episelenurane (a) and/or seleniranium ions (b)], prior to the product-forming step. 

The reaction between a phosphoramidothioate and N-chlorosulfenylcarbamate described in Figure 2 has been applied to methamidophos. In Figure 2, the reaction was used to derivatize a toxic me thyIcarhamate ester by a non-toxic phosphora-midothioate however, in the case of methamidophos the reaction was used to derivatize a toxic phosphoramidothioate with a nontoxic carbamate moiety. The IJ-alkoxycarbonyl-IJ -alkylamino-sulfenyl derivatives of methamidophos thus prepared, where R... 

The results of a comparative metabolism study of an aryl-sulfenyl derivative of carbofuran [2,2-dimethy1-2,3-dihydro-benzofuranyl-7 -methyl-N-(2-toluenesulfenyl)carbamate] in the house fly and white mouse Indicated the selective action of this compound to be a consequence of different metabolic pathways in insects and mammals (12). The arylsulfenyl group on the carbamate moiety allows the mammal to carry out metabolic reactions leading to less toxic products which are rapidly conjugated, while the toxic parent methylcarbamate is formed in the insect. 

Photolysis of phenacyl sulfides [125] and the base-mediated 1,2 elimination reaction of sulfenyl derivatives [126] are other general methods of preparation of these reactive species. 

Sulfenyl derivatives to protect amines, 251, 377-379 to protect thiols, 303-305 S-Sulfenylthiocarbonate esters, to protect thiols, 303-304 Sulfhydryl groups, see Thiols 4-Sulfobenzyl esters, to protect carboxyl groups, 259-260... 

Other sulfenyl derivatives undergo addition to alkenes in a rraws -stereoselective manner. For example, 2,4-dinitrobenzenesulfenyl thiocyanate, on treatment with (Z)- or ( )-2-butene, affords the 1 1 adducts 816a 2,4-dinitrobenzenesulfenyl acetate reacts with cyclohexene to give tram-91 sb. 

The stereoselective tram addition of sulfenyl halides and other sulfenyl derivatives to alkenes can be rationalized by assuming a bridged thiiranium ion, by analogy with the mechanism proposed for stereoselective halogenation of alkenes. 

Table 4. a-Cyano Sulfenylated Derivatives by Reaction of Alkenes with Dimethyl(methylthio)sulfo-nium Tetrafluoroborale and a Cyanide Nucleophile40... 

Alcohols, including tertiary alcohols, react readily with the reagent. The reagent adds stereospecifically (Irons) to unhindered olefins, for example, to the 2-butenes tetrasubstituted olefins do not react. The reagent can be used for Friedel-Crafts substitution of aromatic compounds, including azulene. The 2,4-dinitrobenzene-sulfenyl derivatives formed are colored solids readily purified by crystallization or chromatography and hence are useful for purposes of identification. 

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