Synthesis of polymer microspheres functionalized with chiral ligand by precipitation polymerization and their application to asymmetric transfer hydrogenation

Abstract

Monodisperse, crosslinked poly(divinylbenzene) and poly(methacrylic acid-co-ethylene glycol dimethacrylate) microspheres with (1R,2R)-N1-toluenesulfonyl-1,2-diphenylethylene-1,2-diamine ((R,R)-TsDPEN) moiety were successfully prepared by precipitation polymerization. Introduction site of the (R,R)-TsDPEN moiety into the polymer microspheres could be controlled by changing the order of addition of the corresponding monomers. The functionalized polymer microspheres were applied to asymmetric transfer hydrogenation of ketone and imine. Polymer microsphere-supported chiral catalysts showed good reactivity and enantioselectivity in the catalytic asymmetric transfer hydrogenations. Chiral secondary alcohol was quantitatively obtained with 94% ee in the asymmetric transfer hydrogenation of acetophenone in water. We also found that introduction site of the chiral catalyst and hydrophobicity of the microspheres, as well as degree of the crosslinking, affected the yield and enantioselectivity of chiral product in this reaction. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3340–3349, 2010