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 a cid, suitably carried out at room temperature in the presence of cyclo hexene, trans-hex-3-ene, hex-1-ene and 3,3-dimethylbut-1-ene, results in quantitative isolation of corresponding 2-bromoalkyl phenyl sulfide s which occur with trans-stereospecificity and anti-Markovnikov regios pecificity through electrophilic addition of initially-formed benzenes ulfenyl bromide to the alkene double bond. Similar reaction in the pre sence of mono- and di- substituted alkyl- and phenyl-acetylenes genera lly affords (E)-2-bromovinyl phenyl sulfides in good yields, which bec ome lower with decreasing nucleophilic power of the alkyne employed. H owever, in the presence of parent acetylene, no virtual formation of t he corresponding sulfide adduct occurs, but almost exclusive formation of diphenyl disulfide essentially ascribable to preferred decompositi on of the highly unstable benzenesulfenyl bromide intermediate. The pr esent additions of benzenesulfenyl bromide to alkenes and alkynes are believed to involve the initial intermediacy of thiiranium- and thiire nium-like ions, respectively, by analogy with related AdE reactions of sulfenyl chlorides.