Dimerization of methylstyrenes by acetyl perchlorate and trifluoromethanesulfonic acid

Abstract

AbstractRing‐substituted methylstyrenes (p‐, m‐, and o‐methylstyrenes) in conjunction with acetyl perchlorate (AcClO4) or trifluoromethanesulfonic acid as catalysts gave their linear unsaturated dimer in high yield in benzene at temperatures from 50 to 70°C. In particular, the yield of o‐methylstyrene dimer was as high as 90% in the AcClO4 catalysis at 50°C. The dimer yield depended on solvent and catalyst. The terminal structures of the dimers and higher oligomers were analyzed by NMR spectroscopy. Oligomers with a cyclic terminal structure increased in the products at higher temperature. The dimer yield was improved by codimerizing p‐methylstyrene with less reactive m‐methylstyrene or styrene with AcClO4 catalyst. The dimers obtained partly consisted of linear unsaturated codimers.