SYNTHETIC UTILITY OF 4'-NITROBENZENESULFENANILIDE IN THE FUNCTIONALIZATION OF CARBON-CARBON DOUBLE AND TRIPLE BONDS - ITS USE IN THE BROMOSULFENYLATION OF ALKENES AND ALKYNES

The reaction of 4'-nitrobenzenesulfenanilide (NBSA) with hydrobromic acid, suitably carried out at room temperature in the presence of cyclohexene, trans-hex-3-ene, hex-1-ene and 3,3-dimethylbut-1-ene, results in quantitative isolation of corresponding 2-bromoalkyl phenyl sulfides which occur with trans-stereospecificity and anti-Markovnikov regiospecificity through electrophilic addition of initially-formed benzenesulfenyl bromide to the alkene double bond. Similar reaction in the presence of mono- and di- substituted alkyl- and phenyl-acetylenes generally affords (E)-2-bromovinyl phenyl sulfides in good yields, which become lower with decreasing nucleophilic power of the alkyne employed. However, in the presence of parent acetylene, no virtual formation of the corresponding sulfide adduct occurs, but almost exclusive formation of diphenyl disulfide essentially ascribable to preferred decomposition of the highly unstable benzenesulfenyl bromide intermediate. The present additions of benzenesulfenyl bromide to alkenes and alkynes are believed to involve the initial intermediacy of thiiranium- and thiirenium-like ions, respectively, by analogy with related AdE reactions of sulfenyl chlorides.