ORGN 23 |
| Catalytic tandem asymmetric reactions constitute a powerful strategy for the asymmetric construction of non-adjacent stereocenters in acyclic molecules directly from achiral precursors. In this talk, we present a highly enantioselective and diastereoselective addition of trisubstituted carbon donors to 2-chloroacrylonitrile catalyzed by bifunctional cinchona alkaloid catalysts. The reactions of a variety of sterically and electronically different Michael donors could provide the 1,4-adducts in 4:1-25:1 dr and up to 99% ee. This represents the first asymmetric tandem conjugate addition-protonation with efficient catalytic control of two non-adjacent stereocenters. As demonstrated in a concise and highly stereoselective formal total synthesis of (-)-manzacidin A in this talk, this asymmetric tandem reaction establishes a new and versatile catalytic approach for the enantioselective and diastereoselective creation of 1,3-tertiary-quaternary stereocenters. |
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Asymmetric Reactions and Syntheses
8:00 AM-12:20 PM, Sunday, 10 September 2006 Moscone Center -- Room 131, Oral
Division of Organic Chemistry |