Large-pore mesoporous ethane-silicas as efficient heterogeneous asymmetric catalysts

Add time:09/06/2019    Source:sciencedirect.com

Large-pore mesoporous ethane-silicas with trans-(1R,2R)-diaminocyclohexane protruding in the channel were synthesized by one-step condensation of 1,2-bis(trimethoxysilyl)ethane and N-[(triethoxysilyl)propyl]-(-)-(1R,2R)-diaminocyclohexane in acidic medium using P123 as template. Mesoporous materials are used as catalysts for the asymmetric transfer hydrogenation (ATH) of acetophenone after complexing [Rh(cod)Cl]2. The catalyst with SBA-15 type mesostructure exhibits higher activity, compared to the catalyst with MCM-41 type mesostructure. The post-decoration of trans-(1R,2R)-diaminocyclohexane in the pore of SBA-15 type mesoporous material was further demonstrated by reacting with p-toluenesulfonyl chloride. The modified material (complexed with [RuCl2(p-cymene)]2) gives an enhanced 66% ee (R) for the ATH of acetophenone under air atmosphere in HCOONa-H2O, while only 2% ee (S) is observed on the original material under identical reaction conditions.

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