title: Remarkably stable chiral zirconium complexes for asymmetric Mannich-type reactions.
abstract: Isolable, air-stable, storable, and highly selective chiral zirconium catalysts for asymmetric Mannich-type reactions have been developed. The reactions of imines with silicon enolates proceeded smoothly using 1-10 mol % of the powdered zirconium catalyst to afford the corresponding adducts in high yields with high stereoselectivities. The catalyst could be recovered and reused without significant loss of activity. On the other hand, zirconium single crystals for X-ray analysis were obtained, and the crystals also showed high performance in the asymmetric Mannich-type reactions. Although NMR analyses of these zirconium catalysts showed different structures in dichloromethane, the formation of the same key intermediate from the different catalysts was indicated.
authors.affiliation: Graduate School of Pharmaceutical Sciences, The University of Tokyo, The HFRE Division, ERATO, Japan Science Technology Agency (JST), Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Kowichiro
authors.initials: K
authors.lastname: Saruhashi
authors.forename: Shu
authors.initials: S
authors.lastname: Kobayashi
mesh_terms: D009682:Magnetic Resonance Spectroscopy; D013237:Stereoisomerism; D015040:Zirconium / Q000737:chemistry*
chemical_list: D015040:Zirconium