Asymmetric Strecker reaction of N-benzlhydrylimines utilising new tropos biphenyldiol-based ligands

The synthesis of a library of N-arenesulfonyl-1,3-oxazolidinyl- substituted biphenyldiols is presented. A set of two central intermediates together with easily accessible N-arenesulfonylamino alcohols furnish a broad variety of 1,3-oxazolidines. These are applied as chiral tropos ligands in a titanium-mediated Strecker-type reaction of N-benzhydrylimines. A correlation between the ee values in the product and the diastereomeric ratio concerning the chiral axis of the ligand is made. Those substituents in the ligand which proved to lead to a higher preference for one diastereomeric conformer of the chiral axis in related compounds now provide the most selective ligands. Two privileged ligands are identified that afford superior results in 8 of 13 screenings. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008.