Novel diamino and diimino thioethers - Chiral tridentate ligands for asymmetric Michael reactions?

Novel C-2-symmetric enantiopure beta,beta'-diamino thioethers 1 and beta,be ta'-diimino thioethers 2 have been prepared from chiral alpha-amino acids. Nine of these compounds have been screened as ligands, in combination with 13 metal salts, with a view to achieving the enantioselective catalysis of a Michael reaction of a beta-oxo ester with methyl. vinyl ketone resulting in an optimal ee of 17%.