Aldol Reaction
In the aldol reaction, the diastereoselectivity of the product is often dictated by the geometry of the enolate according to the Zimmerman-Traxler model. The model predicts that the Z enolate will give syn products and that E enolates will give anti products. Chiral Lewis acids allow products that defy the Zimmerman-Traxler model, and allows for control of absolute stereochemistry. Kobayashi and Horibe demonstrated this in the synthesis of dihydroxythioester derivatives, using a tin-based chiral Lewis acid.
The transition structures for reactions with both the R and S catalyst enantiomers are shown below.
Read more about this topic: Chiral Lewis Acid, Applications of CLAs in Asymmetric Synthesis
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