Facile Synthesis of Hybrid Core-Shell Nanospheres for the Asymmetric Transfer Hydrogenation of Aromatic Ketones

The polymer-inorganic hybrid core-shell nanospheres with N-(para-toluenesulfonyl)-1,2-diphenylethylenediamine in the core and the poly(methyl acrylate) (PMA) polymer in the shell were prepared by using a sol-gel process. The surface properties of solid catalysts were modified by controlling PMA and the cetyltrimethylammonium bromide surfactant in the shell. The water contact angle results suggest that the presence of PMA and cetyltrimethylammonium bromide in the shell increases the surface hydrophobicity. In the Rh-catalyzed transfer hydrogenation of aromatic ketones in aqueous HCOONa, the solid catalyst with higher surface hydrophobicity demonstrates higher activity, which suggests that suitable surface properties increase the reaction rate by increasing the diffusion rates of hydrophobic substrates. Furthermore, this heterogeneous catalyst can be reused conveniently without loss of ee values.