title: Highly diastereoselective mannich-type reactions of chiral N-acylhydrazones.
abstract: The Lewis acid-mediated addition of silyl enolates to easily accessible homochiral N-acylhydrazones derived from 3-amino-2-oxazolidinones proceeded in yields up to 71% and diastereomeric ratios of 99:1. In most cases, optimal reaction conditions entailed the simple use of ZnCl(2) in acetonitrile at room temperature. Hydrazones derived from phenyl-, isopropyl-, and benzyl-substituted 2-oxazolidinones were examined in the reaction in terms of yield and diastereoselectivity. The facile SmI(2)-mediated N-N bond cleavage of the formed hydrazines was demonstrated yielding a beta-amino acid derivative. Hence, the overall reaction sequence constitutes an efficient asymmetric Mannich-type reaction. The sense of diastereoselectivity was explained by a preferential attack on the less shielded Si face of the chiral hydrazones and confirmed by means of X-ray crystallography.
authors.affiliation: Department of Chemistry, University of Aarhus, Langelandsgade 140, 8000 Aarhus C, Denmark.
authors.forename: Mikkel F
authors.initials: MF
authors.lastname: Jacobsen
authors.forename: Liviu
authors.initials: L
authors.lastname: Ionita
authors.forename: Troels
authors.initials: T
authors.lastname: Skrydstrup
mesh_terms: D000596:Amino Acids / Q000138:chemical synthesis*; D018360:Crystallography, X-Ray; D006834:Hydrazines / Q000737:chemistry*; D007202:Indicators and Reagents; D009682:Magnetic Resonance Spectroscopy; D008352:Mannich Bases / Q000737:chemistry*; D015394:Molecular Structure; D013237:Stereoisomerism
chemical_list: D000596:Amino Acids; D006834:Hydrazines; D007202:Indicators and Reagents; D008352:Mannich Bases