Double asymmetric induction involves a reaction where two or more existing chiral centers influence the stereochemical outcome. The relationship between these chiral centers (either working cooperatively or antagonistically) can lead to different outcomes, such as enhancing selectivity or creating stereochemical mismatches. The overall stereochemical result depends on the spatial arrangement and interaction between these chiral elements.
An example of double asymmetric induction can be seen in the reaction between a chiral enolate and a chiral electrophile. If both the enolate and the electrophile have pre-existing chiral centers, their interaction can lead to various stereochemical outcomes. A notable case is the reaction between a chiral oxazolidinone auxiliary (Evans’ auxiliary) and a chiral electrophile, such as a chiral aldehyde. The stereochemical outcome depends on whether the chiral centers work in concert to enhance selectivity or oppose each other, potentially leading to reduced stereocontrol or even stereochemical mismatches.