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

Acetylene carbonyl compounds ArCCCOR (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: HSO3F, CF3SO3H, HSO3F–SbF5, CF3SO3H–SbF5, HAlBr4) with a wide range of acidity (Ho ∼ −11 to −22). The vinyl cations react with arenes Ar’H with the formation of alkenylation products ArAr’CCHCOR. On the contrary to protic superacids Lewis acids (AlBr3, AlCl3) activate additionally electrophilic center at carbonyl carbon of the compounds ArCCCOR that leads to the formation of substituted indenes in their reactions with arenes.

Graphical abstractAcetylene 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.Figure optionsDownload full-size imageDownload as PowerPoint slide