(R)-(+)-binol-functionalized mesoporous organosilica as a highly efficient pre-chiral catalyst for asymmetric catalysis

(R)-(+)-Binol-functionalized chiral periodic mesoporous organosili-cas (PMOs) with different framework compositions were successfully synthesized by cocondensation of (R)-2,2′-di(methoxymethyl)oxy-6,6'-di(1-propyl- trimethoxysilyl)-1,1'-binaphthyl (BSBi-nol) with 1,2-bis(trimethoxysilyl)ethane (BTME) and tetramethoxysilane (TMOS) using triblock copolymer P123 as a template in acidic solution. The mixture of BTME and BSBinol can result in a highly ordered mesostructure in an acidic medium but the mesoporous materials synthesized using a mixture of TMOS and BSBinol can only be obtained in a weak acidic buffer solution. All the materials are efficient catalysts (coordinated with Ti) for asymmetric addition of diethylzinc to aldehydes. The chiral PMO with ethane and (R)-(+)-Binol in the framework exhibits an enantioselectivity as high as 90 % with a turnover frequency (TOF) of 104 h^-1, which is even higher than the homogeneous (R)-(+)-Binol catalyst (83 % ee with TOF of 96 h^-1) using toluene as solvent under similar conditions. This work demonstrates the positive effect of the rigid pore wall in increasing the enantioselectivity of the chiral PMOs.