Vinyl type cations generated in superacid HSO₃F by the protonation of the triple bond of acetylene compounds efficiently react with arylammonium ions and N-arylacetamides yielding alkenylation products of the aromatic rings in the given amino derivatives. The regio-and stereoselectivity of electrophilic aromatic substitution was investigated involving vinyl type cations and arylammonium ions or N-arylacetamides in HSO₃F.