In the aldol reaction, the diastereoselectivity of the product is often dictated by the geometry of the enolate. The Zimmerman–Traxler model predicts that the Z enolate will give syn products, and that E enolates will give anti products. Reactions catalyzed by tin-based CLAs allow products to deviate from this pattern.
The transition structures for reactions with both the R and S catalyst enantiomers are: