-
[show abstract]
[hide abstract]
ABSTRACT: A Ag-based chiral catalyst promotes efficient and highly enantioselective aldol additions of ketone-derived enolsilanes to alpha-ketoesters in the presence of a readily available amino acid-based ligand and commercially available AgF2. alpha-Ketoester substrates may bear alkyl, alkenyl, and aryl substituents; reactions proceed to >98% conversion to afford the desired tertiary alcohols in 61->98% isolated yield and 60-96% ee. In contrast to previously reported approaches, highest enantioselectivities are observed with sterically demanding substrates, and reactions can be carried out in undistilled solvent, in air with as little as 1 mol % catalyst.
Journal of the American Chemical Society 06/2006; 128(20):6532-3. · 9.91 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Readily available chiral amino acid-based ligands are used in metal-catalyzed additions of alkylzinc reagents to various aromatic and aliphatic imines; the desired amine products are formed efficiently and in high levels of optical purity. In cases where the more Lewis acidic Zr salts afford lower efficiency, Hf-based catalysts deliver significantly higher yields with similar enantioselectivities. Critical structural features of the N-activating groups as well as the optimal chiral ligands are discussed. A mechanistic working model is presented to rationalize the existing data and to serve as a predictive tool.
Advanced Synthesis & Catalysis 02/2005; 347(2‐3):417 - 425. · 6.05 Impact Factor
-
Angewandte Chemie International Edition 10/2003; 42(35):4244-7. · 13.45 Impact Factor
