Chiral mercaptoaryl-oxazolines as ligands in enantioselective copper-catalyzed 1,4-additions of Grignard reagents to enones

A series of chiral enantiomerically pure mercaptoaryl-oxazolines has been synthesized. Copper(I) thiolate complexes derived from these ligands proved to be efficient catalysts for the 1,4-addition of Grignard reagents to cyclic enones. Enantioselectivities increased in the sequence cyclopentenone (16–37% ee) < cyclohexenone (60–72% ee) < cycloheptenone (83–87% ee).