Vinyl type cations ArC⁺=CHCOR generated from acetylene ketones ArC⁺ = CCOR in superacids HSO₃F and CF₃SO ₃H react with diverse benzene derivatives to form alkenylation products, E-/Z-isomers of diarylpropenone structures Ar(Ar')C=CHCOR. The alkenylation of aromatic compounds with acetylene ketones in superacids occurs with the primary syn-addition of a hydrogen and an aryl residue to the acetylene bond followed by transformation of the product into anti-isomer under the conditions of the reaction.