title: Comparing various chiral dirhodium tetracarboxylates in the dirhodium method.
abstract: Three enantiopure dirhodium tetracarboxylates are compared in their NMR properties to differentiate chiral ligands of various kinds (dirhodium method). The complex with four (S)-2-methoxy-2-(1-naphthyl) propionate (MalphaNP) residues (Rh2) is slightly better for strong donors than the complex with four Mosher acid anions (Rh1), but it is inferior for weak donors. On the other hand, the dirhodium tetracarboxylate complex with four (S)-N-phthaloyl-(S)-tert.-leucinate residues (Rh3) is generally more effective than Rh1. These results are explained by the estimated conformational behavior of the substituents within the equatorial acid residues and the anisotropy (ring-current) effect of aryl groups.
authors.affiliation: Institute of Organic Chemistry, Leibniz University Hannover, Hannover, Germany.
authors.forename: Jens T
authors.initials: JT
authors.lastname: Mattiza
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Harada
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Kuwahara
authors.forename: Zahid
authors.initials: Z
authors.lastname: Hassan
authors.forename: Helmut
authors.initials: H
authors.lastname: Duddeck