Synthesis of chiral tridentate oxazolines with thioether and heteroaryl donor groups and their application in the catalysis of asymmetric Michael reactions
Four chiral amino alcohols 1 derived from the natural α-amino acids L-cysteine and L-methionine have been converted with 2-thiophene and 2-pyridine carboxylic acid derivatives 2 to give eight tridentate oxazoline ligands 3a-d and 4a-d with a heteroaryl and a thioether donor function. In one case the coordination geometry at copper(II) was established by X-ray single crystal structure analysis. All