AEI 60 |
| Mechanistic and synthetic endeavors towards the kinetic resolution of racemic 3-methyl-substituted-1-alkenes using C1- and C2-symmetric zirconocene polymerization catalysts will be presented. Specifically, mechanistic studies probing the relative contribution of chain end and enantiomorphic site control as well as inefficient site epimerization were carried out for C1-symmetric catalysts which had previously been shown to effect kinetic resolution with selectivities as high as 15 for 3,4-dimethyl-1-pentene. Results from these studies indicate that inefficient site epimerization does not limit kinetic resolution while chain end control can be an important source of chiral induction generally working cooperatively with enantiomorphic site control. To avoid some of the issues that C1-symmetric catalysts present, enantiopure C2-symmetric zirconocenes were synthesized, and polymerization of 3-substituted-1-alkenes with ((S,S)-1,2-ethylene-bis-indene)ZrCl2 (((S,S)-EBI)ZrCl2) as the precatalyst displayed some kinetic resolution (kS/kR = 1.5 – 4). Initial results indicate that racemization of the zirconocene does not occur during polymerization making synthesis of more sophisticated catalysts based on (EBI)ZrCl2 possible.
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Academic Employment Initiative
8:00 PM-10:00 PM, Monday, August 20, 2007 BCEC -- Exhibit Hall - B2, Sci-Mix
Academic Employment Initiative |
