620594-45-8Relevant academic research and scientific papers
Employing the structural diversity of nature: Development of modular dipeptide-analogue ligands for ruthenium-catalyzed enantioselective transfer hydrogenation of ketones
Pastor, Isidro M.,Vaestilae, Patrik,Adolfsson, Hans
, p. 4031 - 4045 (2007/10/03)
A library of novel dipeptideanalogue ligands based on the combination of tert-butoxycarbonyl(N-Boc)-protected a-amino acids and chiral vicinal amino alcohols were prepared. These highly modular ligands were combined with [{RuCl2(p-cymene)}2 and the resulting metal complexes were screened as catalysts for the enantioselective reduction of acetophenone under transfer hydrogenation conditions using 2-propanol as the hydrogen donor. Excellent enantioselectivity of 1-phenylethanol (up to 98% ee) was achieved with several of the novel catalysts. Although most of the ligands contained two stereocenters, it was demonstrated that the absolute configuration of the product alcohol was determined by the configuration of the amino acid part of the ligand. Employing ligands based on L-amino acids generated S-configured products, and catalysts based on Damino acids favored the formation of the R-configured alcohol. The combination N-Boc-L-alanine and (R)-phenylglycinol (Boc-L-Ab) or its enantiomer (N-Boc-D-alanine and (S)-phenylglycinol, Boc-D-Aa) proved to be the best ligands for the reduction process. Transfer hydrogenation of a number of aryl alkyl ketones were evaluated and excellent enantioselectivity, up to 96 % ee, was obtained.
Novel highly modular C2-symmetric oxazoline ligands - Application in titanium-catalyzed diethylzinc additions to aldehydes
Pastor, Isidro M,Adolfsson, Hans
, p. 1743 - 1746 (2007/10/03)
Novel C2-symmetric tetradentate bis-oxazoline ligands were efficiently prepared from α-amino acids, 1,2-amino alcohols and 1,2- or 1,3-diacids. The ligands were employed in the titanium-catalyzed addition of diethylzinc to benzaldehyde, and depending on conditions used, moderate to high enantioselectivities of the formed 1-phenylpropanol were obtained.
