ORGN 928 |
| We wish to present two recent studies describing the catalytic asymmetric alpha-vinylation and alpha-alkynylation of enolates, respectively. The allylic and propargylic stereocenters resulting from these unprecedented processes are not easily constructed by other means and may thus provide interesting starting points for stereoselective synthesis. Importantly, the alkynylation enables the formal addition of an ethynyl-unit to the carbonyl compound through strategic removal of a suitable activating group (EWG). We will outline the design of a highly enantioselective Phase-Transfer Catalyst (PTC) based on the cheap and readily accessible Cinchona alkaloid scaffold for these processes and furthermore demonstrate that this new catalyst is in fact very general for the enantioselective alpha-functionalization of cyclic 1,3-dicarbonyl compounds. Finally, we will demonstrate the use of this methodology in complex molecule synthesis and show that it may provide the chemist with a retrosynthetic advantage when constructing structures traditionally accessed through Michael-type reactions.
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Asymmetric Reactions and Syntheses
8:00 AM-12:00 PM, Thursday, August 23, 2007 BCEC -- 253A, Oral
Division of Organic Chemistry |
