Spherical siliceous mesocellular foam (MCF) was synthesized by simple modification of the conventional method and partially surface-modified with trimethylsilyl (TMS) groups prior to the immobilization of chiral bisoxazoline (box). Following the ligand immobilization, the support was postcapped with TMS groups by vapor-phase grafing. This two-step modification of siliceous MCF support led to superior catalyst enantioselectivity. The resulting MCF-immobilized box-Cu(I) catalyst provided 95% ee for trans isomer and 92% ee for cis isomer, and 80% yield for the asymmetric cyclopropanation of styrene. It was also successfully recycled 12 times without losing any enantioselectivity and reactivity. The partial TMS precapping of MCF represents an effective means of preparing a suitable silica support for immobilizing a wide variety of chiral box ligands and nitrogen-containing ligands. This approach can be applied to achieve well-dispersed chiral ligands without strong interactions with the silica surface, so that excellent enantioselectivity, reactivity and recyclability can be attained.

It is also found that flexibility of linker group, precapping, catalyst loading amount, and postcapping are very important factors to be duely considered to get an excellent heterogeneous catalyst in the case of immobilization of chiral azabox. The optimal MCF-supported azabox-Cu(I) catalyst offered as high enantioselectivity and yield as the homogeneous counterpart, and excellent recyclability. This study demonstrated that silica-supported catalysts could achieve comparable enantioselectivity and yield as their homogeneous counterparts through proper design. In addition, the heterogenized catalyst with the optimal ligand loading density could attain superior chemoselectivity in a short reaction time with increased productivity. The optimal heterogenized catalyst was successfully applied to a circulating flow-type packed bed reactor, while retaining the attractive enantioselectivity, yield and recyclability. The circulating flow-type reactor was more suitable than the conventional continuous flow reactor for gas-generating processes, such as the cyclopropanation reaction.