Base catalysis via amine-functionalized mesoporous silicas with various structural phases

Abstract

Abstract Chloropropyl functionalized mesoporous silicas with various structural phases such as hexagonal p6mm, cubic Ia3d, and cubic Im3m have been synthesized from the co-condensation of sodium metasilicate and 3-chloropropyltrimethoxysilane (CPTS) in a P123 or F127/HCl/H2O system. The mesostructural phase of the mesoporous silicas was closely related with the amount of CPTS in the initial synthesis gels when P123 was used as the structure directing agent. On the other hand, the amount of CPTS did not alter the mesostructure of the materials when F127 was used as the structure directing agent. The tetraalkyl quaternary ammonium hydroxide functionalized mesoporous silica catalysts were prepared from the obtained chloropropyl-functionalized mesoporous silicas. Over these catalysts we conducted Claisen-Schmidt condensation of benzaldehyde and 2'-hydroxyacetophenone and subsequent Michael addition to give a pharmaceutically important flavanone compound. The catalyst with Ia3d phase showed higher catalytic activity which was supposed due to the favorable diffusion and mass transfer of substrate molecules into the bicontinuous cubic interwoven pore structure than other cubic and hexagonal structures.