Highly active hybrid mesoporous silica-supported base organocatalysts for C-C bond formation

[EN] New base hybrid catalysts, based on silyl-derivatives of molecules carrying amino, diamino, pyrrolidine, pyrazolium and imidazolium functionalities have been successfully achieved through post synthetic grafting onto M41S-type support. Different characterization techniques were implemented to study the characteristics of the materials, such as elemental analysis, solid state MAS NMR and FTIR spectroscopies, X-ray diffraction (XRD), thermogravimetric and differential thermal analyses (TGA-DTA) and textural properties through N-2 physisorption analysis. The catalytic activity and recyclability of these compounds as base catalysts was demonstrated for C-C bond forming reactions such as Knoevenagel condensations and Michael additions rationalizing the differences observed as function of the reaction mechanisms. An enamine mechanism was proposed for Knoevenagel condensations and an enolate mechanism for Michael additions. The authors are grateful for financial support from the Spanish Government by MAT2017-82288-C2-1-P and Severo Ochoa Excellence ProgramSEV-2016-0683. The authors thank the MULTY2HYCAT (EUHorizon 2020 funded project under grant agreement no. 720783). A. E. acknowledges "La Caixa" foundation for PhD scholarship. Erigoni, A.; Hernández Soto, MC.; Rey Garcia, F.; Segarra-Almela, MDLC.; Díaz Morales, UM. (2020). Highly active hybrid mesoporous silica-supported base organocatalysts for C-C bond formation. Catalysis Today. 345:227-236. https://doi.org/10.1016/j.cattod.2019.09.041 Díaz, U., Brunel, D., & Corma, A. (2013). Catalysis using multifunctional organosiliceous hybrid materials. Chemical Society Reviews, 42(9), 4083. doi:10.1039/c2cs35385g Férey, G. (2008). Hybrid porous solids: past, present, future. Chem. Soc. Rev., 37(1), 191-214. doi:10.1039/b618320b Loy, D. A., & Shea, K. J. (1995). Bridged Polysilsesquioxanes. Highly Porous Hybrid Organic-Inorganic Materials. Chemical Reviews, 95(5), 1431-1442. doi:10.1021/cr00037a013 Hoffmann, F., Cornelius, M., Morell, J., & Fröba, M. (2006). Silica-Based Mesoporous Organic–Inorganic Hybrid Materials. Angewandte Chemie International Edition, 45(20), 3216-3251. doi:10.1002/anie.200503075 Wight, A. P., & Davis, M. E. (2002). Design and Preparation of Organic−Inorganic Hybrid Catalysts. Chemical Reviews, 102(10), 3589-3614. doi:10.1021/cr010334m Vallé, K., Belleville, P., Pereira, F., & Sanchez, C. (2006). Hierarchically structured transparent hybrid membranes by in situ growth of mesostructured organ