Dimerization of methylstyrenes by acetyl perchlorate and trifluoromethanesulfonic acid

Abstract

Abstract Ring‐substituted methylstyrenes ( p ‐, m ‐, and o ‐methylstyrenes) in conjunction with acetyl perchlorate (AcClO 4 ) 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 AcClO 4 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 AcClO 4 catalyst. The dimers obtained partly consisted of linear unsaturated codimers.