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Study on the enantioselective oligomerization of 1‐butene by chiral non‐racemic Ti complexes fixed on MgCl 2
Author(s) -
Fuhrmann Hans,
Kortus Karin,
Fuhrmann Christa
Publication year - 1996
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.1996.021971129
Subject(s) - chemistry , monomer , polymer chemistry , enantioselective synthesis , polymerization , enantiomer , enantiomeric excess , medicinal chemistry , catalysis , stereochemistry , organic chemistry , polymer
Abstract A number of chiral non‐racemic titanium complexes of the type (R * O) 2 TiCl 2 (R * being an enantiomerically pure monosaccharide derivative) was incorporated in a MgCl 2 matrix by coprecipitation from a non‐solvated n/iso‐Bu 2 Mg solution with CCl 4 . The precatalysts formed were activated with different organoaluminium cocatalysts and used for the oligomerization of 1‐butene. In dependence of the cocatalyst and the temperature various reaction pathways were observed. In most cases saturated oligomers were isolated. At −20°C with i ‐Bu 3 Al 2 OBuCl 2 as cocatalyst 55–65% olefinic oligomers with 50–70% enantiomeric excess (ee) are formed. If the growing chain is terminated by chain transfer to the Al cocatalyst, epimerization of the last inserted monomer occurs, possibly due to a rearrangement which might be favoured by an agostic interaction. The fixation of TiCl 4 to a chiral modified MgCl 2 support does not lead to enantiomerically enriched oligomers under the same reaction conditions.