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- Title
Theoretical Studies on the Diastereoselectivity in the Lewis Acid Catalyzed CarbonylEne Reaction: A Fundamental Role of Electrostatic Interaction.
- Authors
Yamanaka, Masahiro; Mikami, Koichi
- Abstract
Lewis acids affect reactivity, selectivity, and mechanism in the carbonyl-ene reaction. The diastereoselectivity in the glyoxylate-ene reaction depends on Lewis acids. While the SnCl4-promoted reaction can be achieved with a high level of anti-selectivity, the use of Al reagents leads to a high syn-selectivity. The origin of the Lewis acid dependency of the diastereoselectivity in the carbonylene reaction of ( E)-but-2-ene with glyoxylate was theoretically studied (HF/6-31G*) from the point of view of differences and similarities between the ene and the Diels-Alder reactions. Though it has been widely accepted that the endo-preference would be less obvious in the ene reaction than in the Diels-Alder reaction, our ab initio molecular studies showed that the electrostatic interaction between carbonyl O-atom lone pair and cationic allylic central C-atom of ene component exists in the Lewis acid-promoted carbonyl-ene reaction to affect the transition-state conformation. It is illustrated that such an electrostatic interaction is essential to control the exo/ endo-selectivity, which provides the diastereoselectivity of the product in the transition state of the Lewis acid promoted carbonylene reaction.
- Publication
Helvetica Chimica Acta, 2002, Vol 85, Issue 12, p4264
- ISSN
0018-019X
- Publication type
Article
- DOI
10.1002/hlca.200290011