The oligomerization of isoprene with modified ziegler catalysts

Abstract

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.