ORGN 22 |
| Li Deng, Shi Kai Tian, and Ran Hong. Department of Chemistry, Brandeis University, 415 South Street, Waltham, MA 02454-9110 |
| The development of broadly applicable and practical catalytic approaches for the enantioselective creation of quaternary stereocenters remains a highly desirable yet challenging goal. In this Communication, we describe a highly enantioselective cyanosilylation of acetal ketones (α, α-dialkoxy ketones) catalyzed by modified cinchona alkaloids. This reaction is the first highly enantioselective cyanosilylation of ketones catalyzed by an organic chiral Lewis base and is found to be highly efficient with acetal ketones bearing a broad range of alkyl, aryl, alkenyl, and alkynyl substituents. This new catalytic asymmetric reaction, coupled with the versatility of the acetal functionality, provides a broadly useful synthetic method for chiral building blocks bearing quaternary stereocenters. Acetal ketones, readily accessible but previously unexplored in asymmetric synthesis, demonstrate unusual reactivity and selectivity toward the nucleophilic cyanosilylation, thereby suggesting that they may be interesting substrates for other catalytic enantioselective reactions. |
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Asymmetric Reactions and Syntheses
8:00 AM-12:00 PM, Sunday, August 22, 2004 Pennsylvania Convention Center -- 201A, Oral
Division of Organic Chemistry |