ORGN 467 |
Asymmetric cyclopropanation of olefins with optically active ruthenium(II) salen complexes
| Jason A. Miller and SonBinh T. Nguyen. Department of Chemistry, Northwestern University, 2145 Sheridan Rd., Evanston, IL 60208 |
Optically pure salen complexes of ruthenium(II) with axial pyridine ligands have been synthesized and characterized. It has been discovered that this is the most versatile asymmetric cyclopropanation system to date. When these ruthenium catalysts were used to cyclopropanate styrene and ethyl diazoacetate (EDA), very high enantiomeric excesses of both cis and trans isomers were produced (>99%). Diastereoselectivity was also exceptional (cis:trans, 1:10.8), while product yield was nearly quantitative. Enantiomeric excess with this catalyst system is among the highest currently reported in the literature. Not only was this system found to cyclopropanate styrene and styrene derivatives, but a host of other olefins were successfully reacted as well, including a range of conjugated, electron-rich, electron-poor, and aliphatic olefins. This cyclopropanation system has also been successfully applied to the synthesis of N-protected beta-amino acid derivatives. Chiral induction studies via catalyst axial ligand substitution are currently underway and mechanistic considerations and activity-related concepts are also being investigated.  |
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Total Synthesis, Asymmetric Reactions and Syntheses, Bioorganic
9:00 AM-11:00 AM, Wednesday, March 31, 2004 Anaheim Convention Center -- Hall C, Poster
Division of Organic Chemistry
The 227th ACS National Meeting, Anaheim, CA, March 28-April 1, 2004
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