STUDY ON THE ENANTIOSELECTIVE OLIGOMERIZATION OF 1-BUTENE BY CHIRAL NON-RACEMIC TI COMPLEXES FIXED ON MGCL2

A number of chiral non-racemic titanium complexes of the type (RO)(2) TiCl2 (R being an enantiomerically pure monosaccharide derivative) wa s incorporated in a MgCl2 matrix by coprecipitation from a non-solvate d n/iso-Bu(2)Mg solution with CCl4. The pre catalysts formed were acti vated with different organoaluminium cocatalysts and used for the olig omerization of 1-butene. In dependence of the cocatalyst and the tempe rature various reaction pathways were observed. In most cases saturate d oligomers were isolated. At -20 degrees C with i-Bu(3)Al(2)OBuCl(2) as cocatalyst 55-65% olefinic oligomers with 50-70% enantiomeric exces s (ee) are formed. If the growing chain is terminated by chain transfe r to the Al cocatalyst, epimerization of the last inserted monomer occ urs, possibly due to a rearrangement which might be favoured by an ago stic interaction. The fixation of TiCl4 to a chiral modified MgCl2 sup port does not lead to enantiomerically enriched oligomers under the sa me reaction conditions.