Substituent effect on oligomerization of isoprene catalyzed by ring-substituted (RCp)(2)TiCl2/i-C3H7MgCl system

Using the catalyst system composed of Cp2TiCl2 and i-C3H7MgCl, isoprene can be oligomerized to a mixture of dimers and higher oligomers. The two dimer s 2,6-dimethyl-1, trans-3,6-octatriene and 3,6-dimethyl-1,3,6-octatriene we re characterised by GC-MS; H-1-NMR; C-13-NMR and GC-IR. The effects of reac tion time, molar ratio of catalyst to isoprene, temperature and solvent on the reaction were discussed. After established the appropriate reaction con dition, the substituent effect of a series of alkyl ring-substituted cyclop entadienyl titanium dichlorides on catalystic activity were investigated. A mechanism of the reaction was also proposed. (C) 2000 Elsevier Science B.V . All rights reserved.