| Abstract: | The oligomerization of isoprene with modified ZIEGLER catalysts was studied. Dimers of isoprene were obtained in 70–90% yield using combined catalysts of diethylaluminum chloride, dimethyl sulfoxide, and a titanium(IV) compound, such as titanium di-(p-toluenesulfonate) dichloride and N-vinylpyrrolidone or alkylene carbonate complexes of titanium tetrachloride. Two isomeric dimers, produced in approximately equal molar ratio, were found as the main product accompanied by small amounts of a third dimer and of trimers. Each dimer was separated by means of preparative gas chromatography and subjected to analyses. The two predominant compounds were identified as 2.4-dimethyl-4-ethenyl-1-cyclohexene and 2.7-dimethyl-1.3.6-octatriene, respectively. Possible mechanisms are discussed in relation to the oligomerization of butadiene on the basis of the product analysis. |
