title: A designer axially chiral amino sulfonamide as an efficient organocatalyst for direct asymmetric anti-selective Mannich reactions and syn-selective cross-aldol reactions.
abstract: A direct asymmetric Mannich reaction using a novel axially chiral amino sulfonamide (S)-3 that is highly anti- and enantioselective has been developed. For instance, in the presence of a catalytic amount of (S)-3, the reactions between aldehydes and alpha-imino esters proceeded smoothly to give anti Mannich products with a significantly higher anti/syn ratio and enantioselectivity than previously possible. By utilizing N-Boc-protected aromatic imines instead of alpha-imino esters, the synthetically useful Boc protecting group and various aromatic or heteroaromatic substituents were installed into the anti Mannich products and consequently the substrate scope of the anti-selective Mannich reaction and the synthetic utility of the anti Mannich products have been expanded. The axially chiral amino sulfonamide (S)-3 has also been successfully applied to asymmetric direct cross-aldol reaction between two different aldehydes. The catalyst (S)-3 has the advantage of giving mainly syn products, whereas proline shows the opposite anti selectivity.
authors.affiliation: Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8502, Japan.
authors.forename: Taichi
authors.initials: T
authors.lastname: Kano
authors.forename: Yukako
authors.initials: Y
authors.lastname: Yamaguchi
authors.forename: Keiji
authors.initials: K
authors.lastname: Maruoka