Abstract
3-Methoxyestra-1,3,5(10)-trien-16-one (6) was converted to the corresponding fulvene (7). Methyllithium was added and the resulting (16α-methylestratrienyl)cyclopentadiene 8 separated by chromatography. Deprotonation gave the (16α-methylestratrienyl-C5H4)Li reagent 9 that was added to 0.5 molar equivalents of ZrCl4(THF)2 to yield bis[-(3-methoxy-16α-methylestra-1,3,5(10)-trien-16ß-yl)cyclopentadienyl]-zirconium dichloride (10, 45%). Complex 10 was activated by treatment with an excess of methylalumoxane. The resulting homogeneous Ziegler-type catalyst was employed for stereo-selective propene polymerization. In the temperature range of -50 to -10°C partly isotactic polypropylene was obtained. A detailed analysis has revealed that stereocontrol is effected by a combination of enantiomorphic site and chain-end control. Compounds 7 and 10 were characterized by X-ray diffraction.
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