title: Highly enantioselective michael additions of indole to benzylidene malonate using simple bis(oxazoline) ligands: importance of metal/ligand ratio.
abstract: [Structure: see text] Simple bis(oxazoline) ligands, especially azabis(oxazolines), can catalyze the copper-catalyzed addition of indoles to benzylidene malonates in up to >99% ee, provided that excess of chiral ligand is avoided. The paradigm followed in many asymmetric catalyses that an excess of chiral ligand with respect to the metal should improve enantioselectivity because a background reaction by free metal is suppressed, is not applicable here, which might call for revisiting some of the many copper(II)-bis(oxazoline)-catalyzed processes known.
authors.affiliation: Institut für Organische Chemie, Universität Regensburg, Universitätsstr. 31, 93053 Regensburg, Germany.
authors.forename: Ramesh
authors.initials: R
authors.lastname: Rasappan
authors.forename: Markus
authors.initials: M
authors.lastname: Hager
authors.forename: Anja
authors.initials: A
authors.lastname: Gissibl
authors.forename: Oliver
authors.initials: O
authors.lastname: Reiser
mesh_terms: D001597:Benzylidene Compounds / Q000737:chemistry*; D007211:Indoles / Q000737:chemistry*; D008024:Ligands; D008670:Metals / Q000737:chemistry*; D008958:Models, Molecular; D013237:Stereoisomerism; D014961:X-Ray Diffraction
chemical_list: D001597:Benzylidene Compounds; D007211:Indoles; D008024:Ligands; D008670:Metals; C030374:indole