title: Mechanism of amination of β-keto esters by azadicarboxylates catalyzed by an axially chiral guanidine: acyclic keto esters react through an E enolate.
abstract: The mechanism of the reaction between di-tert-butyl azadicarboxylate and 1,3-dicarbonyl compounds catalyzed by an axially chiral guanidine is investigated by density functional theory methods. The results show that the catalyst acts simultaneously as a Brønsted base and an acid catalyst, and the mechanism is similar to that of the related BINOP organocatalysts. Surprisingly, cyclic and acyclic β-keto esters yield opposite enantiomers; the calculations demonstrate that this is a consequence of the preferred enolate geometry in the transition structures. Literature evidence suggests that other organocatalytic reactions show similar behavior.
authors.affiliation: Chemical Engineering Department, Facultad de Ciencias Químicas, Plaza de los Caídos 1-5, Salamanca E37004, Spain. lsimon@usal.es
authors.forename: Luis
authors.initials: L
authors.lastname: Simón
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Goodman