Different reactivities of acetylene carbonyl compounds under the catalysis by Bronsted superacids and Lewis acids

Abstract Acetylene carbonyl compounds ArC CCOR (R = H, Me, Ph) form vinyl cations ArC + CHCOR or ArC + CHC(OH) + R at the protonation in Bronsted and conjugate Bronsted–Lewis superacids (protic superacids: HSO 3 F, CF 3 SO 3 H, HSO 3 F–SbF 5 , CF 3 SO 3 H–SbF 5 , HAlBr 4 ) with a wide range of acidity ( H o  ∼ −11 to −22). The vinyl cations react with arenes Ar’H with the formation of alkenylation products ArAr’C CHCOR. On the contrary to protic superacids Lewis acids (AlBr 3 , AlCl 3 ) activate additionally electrophilic center at carbonyl carbon of the compounds ArC CCOR that leads to the formation of substituted indenes in their reactions with arenes.