Synthesis and characterization of mesoporous zirconium phosphonates: A novel supported cinchona alkaloid catalysts in asymmetric catalysis

In this paper, cinchonidine (CD) with the different arm lengths (n = 2-6) was covalently immobolized onto the backbone of zirconium phosphonate to afford a series of mesoporous zirconium phosphonates (4a-e) for the first time. It was found that zirconium phosphonates (4a-e) were conglomerated with the globular aggregates with the diameters of about 100-150 nm and possessed the surface areas of 20.8-36.2 m(2) g(-1), pore volumes of 0.219-0.498 cc g(-1) and average pore sizes of 11.7-41.5 angstrom. The TEM' images of 4a-e in organic solvent showed that these materials were easily swollen into the filiform structure with the length about several micrometers and thickness about 30-50 nm. In the field of the asymmetric catalysis, the preliminarily enantioselective addition of diethylzinc to various aldehydes catalyzed by 4a-e (35-62%e.e. in the 68-92% yield) was carried out and can be reused ten times without loss in the yield and enantiomeric excess. (C) 2009 Elsevier B.V. All rights reserved.