Asymmetric Cyclopropanation Catalyzed by MCF-Supported Bisoxazoline-Cu(I)

Significance

Reaction of siliceous mesocellular foams (MCF) 1 with hexamethyldisilazane (HMDS) gave partially TMS-modified MCF 2. Reaction of 2 with trimethoxysilane-modified bisoxazoline (BOX) 3 afforded partially TMS-modified MCF-supported BOX 4, which was treated with HMDS again to provide the MCF-supported BOX 5. Complexation of 5 with CuOTf proceeded smoothly in THF to give the MCF-supported BOX-Cu(I) catalyst. This catalyst showed high catalytic activity and enantio­selectivity in the asymmetric cyclopropanation of styrene (80% yield, trans/cis = 65:35, 95% ee for trans isomer and 92% ee for cis isomer). The catalyst can be recycled 12 times without significant loss of reactivity and enantioselectivity.