ORGN 268 |
| We have recently found that acyclic and cyclic alkyl amino (alkyl-C-NHCs) carbenes can be prepared as stable species, providing they feature a tertiary alkyl group in alpha position to the carbene center. The geometric parameters and the carbonyl stretching frequencies of Rh(cod)Cl and Rh(CO)2Cl complexes, respectively, of these new types of carbenes are in the range observed for corresponding NHC complexes. Because of the presence of a tertiary carbon alpha to the carbene center, alkyl-C-NHCs can be constructed to be more bulky, and can have a center of optical purity closer to the carbene center than NHCs. Moreover, alkyl-C-NHCs can contain a rigid or flexible spirocycle adjacent to the carbene center. All of these structural features, which are unique to alkyl-C-NHCs, make these new carbenes promising ligands for transition metal catalysts. |
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Asymmetric Reactions and Syntheses
8:00 AM-12:00 PM, Monday, 14 March 2005 Convention Center -- Room 11A, Oral
Division of Organic Chemistry |