Large-pore mesoporous organosilicas functionalized with trans-(1R,2R)-diaminocyclohexane:: Synthesis, postmodification, and catalysis

Large-pore mesoporous ethane-silicas functionalized with trans-(1R, 2R)-diaminocyclohexane were synthesized in an acidic medium by one-step co-condensation of 1,2-bis(trimethoxysilyl) ethane and N-[(trimethoxysilyl)benzyl]-(-)-(1R,2R)-diaminocyclohexane using triblock copolymer P123 as template. The postmodification of trans-(1R,2R)-diaminocyclohexane in the pore of the mesoporous ethane-silicas was further demonstrated by reaction with p-toluenesulfonyl chloride. The modified material (complexed with [RhCp*Cl-2](2)) exhibits much higher conversion and ee [53% conversion with 68% ee (R)] than the original material [18% conversion with 38% ee ( S)] for the asymmetric transfer hydrogenation of acetophenone under air atmosphere in HCOONa-H2O. Various aromatic ketones can be converted to the corresponding chiral alcohol with moderate to good enantioselectivities [18-81% ee (R)]. The cocondensation method associated with the postmodification method is one of the alternatives for the synthesis of mesoporous materials containing new functionalities.