Organic–inorganic hybrid catalysts based on ordered porous structures for Michael reaction

Two types of organic–inorganic hybrid base catalysts are prepared for the Michael reaction. Organic-functionalized molecular sieves (OFMSs), particularly “amine-immobilized porous silicates”, are designed based on a common idea of immobilizing active catalytic sites on silicate surface. Silicate-organic composite materials (SOCMs), such as “ordered porous silicate-quaternary ammonium composite materials”, are the precursors of ordered porous silicates obtained during the synthesis. The OFMSs are effective when the supports have large pore volume and/or surface area and the reaction is carried out in polar solvents ethanol and DMF. However, the activity of the OFMSs is considerably low in a non-polar solvent such as benzene. In contrast, the SOCMs are remarkably active in benzene. The organic cation-MCM-41 composite is more active than the composite of an organic cation and a microporous silicate such as zeolite beta and ZSM-12. In the SOCM catalysts, (SiO)3SiO−(+NR4) moieties located at the accessible sites are considered to play some important roles. The active species are absent in the liquid phase after the reaction. The recycle of the catalyst was possible without significant loss of activity when the substrates are enough reactive.

Silicate-organic composite material (SOCM), such as MCM-41-cetyltrimethylammonium composite material, was found to be an effective base catalyst for the Michael reaction of chalcone derivative with malonic ester, whereas aminopropyl-grafted MCM-41 was less active in a non-polar solvent. Figure optionsDownload as PowerPoint slide