title: Theoretical (DFT) insights into the mechanism of copper-catalyzed cyclopropanation reactions. Implications for enantioselective catalysis.
abstract: The mechanism of the copper(I)-catalyzed cyclopropanation reaction has been extensively investigated for a medium-size reaction model by means of B3LYP/6-31G(d) calculations. The starting ethylene complex of the N,N'-dimethylmalonaldiimine--copper (I) catalyst undergoes a ligand exchange with methyl diazoacetate to yield a reaction intermediate, which subsequently undergoes nitrogen extrusion to generate a copper--carbene complex. The cyclopropanation step takes place through a direct carbene insertion of the metal--carbene species to yield a catalyst--product complex, which can finally regenerate the starting complex. The stereochemical predictions of a more realistic model (by considering a chiral bis(oxazoline)--copper (I) catalyst) have been rationalized in terms of steric repulsions, showing good agreement with experimental data.
authors.affiliation: Departamento de Química Orgánica, Instituto de Ciencia de Materiales de Aragón, C.S.I.C.-Universidad de Zaragoza, Pedro Cerbuna 12, E-50009 Zaragoza, Spain.
authors.forename: J M
authors.initials: JM
authors.lastname: Fraile
authors.forename: J I
authors.initials: JI
authors.lastname: García
authors.forename: V
authors.initials: V
authors.lastname: Martínez-Merino
authors.forename: J A
authors.initials: JA
authors.lastname: Mayoral
authors.forename: L
authors.initials: L
authors.lastname: Salvatella