(113c) Base Catalysis With Microporous and Mesoporous Nitrogen-Containing Silicas

Nitrogen-containing silicas having microporous or mesoporous structure have recently attracted attentions as a candidate to catalyze base reactions.  We have recently developed a novel series of porous N-containiing silica catalysts for base-catalyzed Knoevenagel condensation, Aldol condensation, Claisen-Schmidt reaction, Morita-Baylis-Hillman reaction, and so on.  The silamino group, Si-NH-Si, in silicate framework was the catalytically active center, and mesoporous silica having more amount of silanol group, Si-OH, showed preferential properties as a host for the silamino group to dope rather than microporous zeolites.  Further modification of the N atom by substituting H into methyl group, resulting in methyl silamino group, Si-N(CH₃)-Si, led us to a more active and selective catalyst for some specific reactions, which could never be catalyzed by conventional solid base catalysts.  In this presentation, the basicity of such newly functionalized group in silicate framework, and the porosity and crystallinity of the host required for some specific reactions would be discussed.