| Autor: |
Andrey, Olivier, Alexakis, Alexandre, Tomassini, Axel, Bernardinelli, Gerald |
| Zdroj: |
Advanced Synthesis & Catalysis; August 2004, Vol. 346 p1147-1168, 22p |
| Abstrakt: |
The direct Michael addition of aldehydes and ketones to nitroolefins, catalyzed by N-i-Pr-2,2′-bipyrrolidine, is described. The desired 1,4-adducts are obtained in excellent yields with enantioselectivities up to 95% ee and dr up to 95 : 5 of the syn aldehyde addition product. An unexpected inversion of diastereoselectivity was observed for the addition of α-hydroxy ketones to β-arylnitroolefins with enantioselectivities up to 98% ee. The formation of an internal hydrogen bond between the OH group of the α-hydroxy ketone and the tertiary nitrogen of the catalyst leads to the formation of a rigid cis enamine intermediate that accounts for the inversion of the expected diastereoselectivity and the very high ees. |
| Databáze: |
Supplemental Index |
| Externí odkaz: |
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