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 m2 g−1, pore volumes of 0.219–0.498 cc g−1 and average pore sizes of 11.7–41.5 Å. 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.