n→π* Interactions Engender Chirality in Carbonyl Groups

An n→π* interaction stems from the delocalization of the electron pair (n) of a donor group into the antibonding orbital (π*) of a carbonyl group. Crystallographic analyses of five pairs of diastereoisomers demonstrate that an n→π* interaction can induce chirality in an otherwise planar, prochiral carbonyl group. Thus, a subtle delocalization of electrons can have stereochemical consequences.