title: The more gold--the more enantioselective: cyclohydroaminations of γ-allenyl sulfonamides with mono-, bis-, and trisphospholane gold(I) catalysts.
abstract: A series of chiral mono-, di-, and trinuclear gold(I) complexes have been prepared and used as precatalysts in the asymmetric cyclohydroamination of N-protected γ-allenyl sulfonamides. The stereodirecting ligands were mono-, di-, and tridentate 2,5-diphenylphospholanes, which possessed C(1), C(2), and C(3) symmetry, respectively, thereby rendering the catalytic sites in the di- and trinuclear complexes symmetry equivalent. The C(3)-symmetric trinuclear complex displayed the highest activity and enantioselectivity (up to 95 % ee), whilst its mono- and dinuclear counterparts exhibited considerably lower enantioselectivities and activities. A similar trend was observed in a series of mono-, di-, and trinuclear 2,5-dimethylphospholane gold(I) complexes. Aurophilic interactions were established from the solid-state structures of the trinuclear gold(I) complexes, thereby raising the question as to whether these secondary forces were responsible for the different catalytic behavior observed.
authors.affiliation: Anorganisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany.
authors.forename: Lara-Isabel
authors.initials: LI
authors.lastname: Rodríguez
authors.forename: Torsten
authors.initials: T
authors.lastname: Roth
authors.forename: Julio
authors.initials: J
authors.lastname: Lloret Fillol
authors.forename: Hubert
authors.initials: H
authors.lastname: Wadepohl
authors.forename: Lutz H
authors.initials: LH
authors.lastname: Gade