Synthesis of chiral tridentate oxazolines with thioether and heteroaryl donor groups and their application in the catalysis of asymmetric Michael reactions
J. Christoffers et al., Synthesis of chiral tridentate oxazolines with thioether and heteroaryl donor groups and their application in the catalysis of asymmetric Michael reactions, TETRAHEDRON, 55(17), 1999, pp. 5377-5388
Four chiral amino alcohols 1 derived from the natural a-amino acids L-cyste
ine and L-methionine have been converted with 2-thiophene and 2-pyridine ca
rboxylic 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 crysta
l structure analysis. All ligands have been screened with 13 metal compound
s 8 with regard to the asymmetric catalysis of the Michael reaction of a be
ta-keto ester 6 with methyl vinyl ketone (7) to give an optimal result of 1
9% ee. (C) 1999 Elsevier Science Ltd. All rights reserved.