Cyanosulfenylation

An alternative route from alkenes to 2-azasulfides reported by the groups of Caserio and Trost involves addition of a thiosulfonium salt, e.g. dimethyl(methylthio)sulfonium tetrafluoroborate (MeSS-Me2+ BF4-), followed by treatment of the resultant thiosulfenylated adduct with an amine or other nitrogen nucleophiles (Schemes 2320 and 24).35 Trost reports that the addition of the thiosulfonium salt can be followed by addition of an oxygen nucleophile, such as acetate, or a carbon nucleophile, such as cyanide, effecting oxosulfenylation and cyanosulfenylation, respectively (Scheme 25).36... 

Cyanosulfenylation is generally conducted by mixing the alkene with 1 in CH3CN followed by addition of finely powdered NaCN at 25°. Addition of dimethyl sulfide sometimes improves the yield. The adducts are all assumed to be trans, but regioselectivity is a more critical question. With monosubstituted alkenes, only anti-Markovnikov addition is observed. Markovnikov adducts are favored by use of the less nucleophilic (CH3)3SiCN. 

Nucleophilic attack on alkenes initiated by dimethyl(methylthio)sulfonium tetrafluoroborate is also a very efficient method for the addition of carbon nucleophiles to unsaturated systems40,41. The results of cyanosulfenylation of alkenes are collected in Table 440. 

The synthesis of a-methylthionitriles in high yield by cyanosulfenylation , i.e. addition of di-methyl(methylthio)sulfonium tetrafluoroborate to alkenes, followed by reaction with a CN donator, e.g. alkali metal cyanide/HBp4 or TMS-CN (equation 15), was recently described by TrostJ ... 

Diisopropyl l-(isopropoxycarbonyl)methylphosphonate undergoes mono- or disulfenylation with phenyl- or cyanosulfenyl chloride in the presence of Al(O/-Pr2)3 in toluene to give the expected phosphonate in 72-81% yields The reaction of sodium diethyl 1 -(ethoxycarbonyl )inethylphos-phonate with phenylthioiosocyanate has also been reported ... 

Trost BM, Shibata T, Martin SJ. Nucleophibc attack of olefins initiated by dimetbyl(metbyltbio)sulfonium fluoroborate (DMTSF). Cyanosulfenylation and oxy and oxosulfenyla-tion. J. Am. Chem. Soc. 1982 104 3228-3230. 

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