Synthetic and Mechanistic Studies into the Kinetic Resolution of α-olefins Using C₁₋ and C₂₋ Symmetric Zirconocene Polymerization Catalysts

Citation

Byers, Jeffery Allen (2007) Synthetic and Mechanistic Studies into the Kinetic Resolution of α-olefins Using C₁₋ and C₂₋ Symmetric Zirconocene Polymerization Catalysts. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/H55G-7C87. https://resolver.caltech.edu/CaltechETD:etd-05162007-152948

Abstract

Mechanistic and synthetic investigations into the kinetic resolution of racemic α-olefins by polymerization catalysis using C₁₋ and C₂₋symmetric zirconocenes are reported. The importance of chain end control as a stereocontrol element was probed with ethylene and propylene copolymerizations catalyzed by the C₁₋symmetric catalyst, {1,2-(SiMe₂)₂(η⁵-3,5-C₅H₁(CHMe₂)₂)(η⁵-4-C₅H₂((S)-CHMeCMe₃)]}ZrCl₂/MAO. Selectivity factors and pentad analysis of racemic α-olefin and propylene polymerizations catalyzed by a similar C₁₋symmetric catalyst, {1,2-(SiMe₂)₂(η⁵-3,5-C₅H₁(CHMe₂)₂)(η⁵-4-C₅H₂((S)-CHEtCMe₃)]}ZrCl₂/MAO, indicate that site epimerization does not limit selectivity during kinetic resolution.

To avoid some of the issues involved with the C₁₋symmetric catalysts, a route to enantiopure C₂₋symmetric zirconocenes was pursued. With the aid of the chiral auxiliary, (R)-N2,N2’-di-p-tolyl-1,1’-binaphtyl-2,2’-diamine, enantiospecefic synthesis of (S,S)-{C₂H₄ -1,2-(1-indene)₂}ZrCl₂ was accomplished and its use for kinetic resolution was investigated. Although synthetically useful selectivities were not observed, it was determined that the C₂₋symmetric catalyst does not racemize during polymerization, which substantiates a more thorough investigation of catalysts based on {C₂H₄ -1,2-(1-indene)₂}ZrCl₂.

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