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

Acetylene carbonyl compounds react with arenes in Bronsted and conjugate Bronsted–Lewis superacids leading to aromatic alkenylation products. Under the catalysis by Lewis acids the reactions of the acetylene compounds with arenes result in the formation of substituted indenes. ▪ 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 3F, CF 3SO 3H, HSO 3F–SbF 5, CF 3SO 3H–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.