New chiral ferrocenyl amidophosphine ligand for remarkable improvement of enantioselectivities in copper-catalyzed addition of diethylzinc to N-sulfonylimines

(S)-N-Ferrocenoyl-2-[(diphenylphosphino)methyl]-pyrrolidine 3 was conveniently prepared from commercially available l-proline and ferrocenecarboxylic acid. In the presence of a catalytic amount of chiral ligand 3 (4 mol %) and Cu(OTf)2 (3 mol %), the asymmetric addition of diethylzinc to N-sulfonylimines was achieved in 57–99% yield with up to 88% ee.