title: Lithium diisopropylamide-mediated enolization: catalysis by hemilabile ligands.
abstract: Structural, kinetic, and computational studies reveal the mechanistic complexities of a lithium diisopropylamide (LDA)-mediated ester enolization. Hemilabile amino ether MeOCH2CH2NMe2, binding as an eta1 (ether-bound) ligand in the reactant and as an eta2 (chelating) ligand in the transition structure, accelerates the enolization 10,000-fold compared with n-BuOMe. At the onset of the reaction, a dimer-based enolization prevails. As the reaction proceeds, significantly less reactive LDA-enolate mixed dimers appear and divert the reaction through monomer- and mixed dimer-based pathways. The mechanistic and computational investigations lead to a proof-of-principle ligand-catalyzed enolization in which an ancillary ligand allows the catalytic ligand to re-enter the catalytic cycle.
authors.affiliation: Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, USA.
authors.forename: Antonio
authors.initials: A
authors.lastname: Ramirez
authors.forename: Xiufeng
authors.initials: X
authors.lastname: Sun
authors.forename: David B
authors.initials: DB
authors.lastname: Collum
mesh_terms: D002384:Catalysis; D019281:Dimerization; D007700:Kinetics; D008024:Ligands; D011437:Propylamines / Q000737:chemistry*
chemical_list: D008024:Ligands; D011437:Propylamines; C007442:diisopropylamine