A Simple Modification Creates a Great Difference: New Solid-Base Catalyst Using Methylated N-Substituted SBA-15

Abstract

A simple modification, methylation of the nitrogen-substituted mesoporous silica SBA-15, enhances the basicity of a solid-base catalyst. The methyl group donates an electron to the nitrogen atom in the silica framework. This catalyst accelerates Knoevenagel condensation using benzaldehyde and diethyl malonate, which conventional solid-base catalysts reported to date cannot do. This report demonstrates a possible new type of base catalyst using nitrogen-substituted mesoporous silica materials.

Design and fabrication of mesoporous heterogeneous basic catalysts

“…Under the catalysis of the optimum material, the conversion achieved 96% with 100% selectivity of 1,1-dicyanophenylethylene after reaction at 60 1C for 3 h. 157 This activity was higher than that of the typical solid base MgO, which showed the conversion of about 70% under the same conditions. 172 These results clearly reveal that the basicity of nitridated mesoporous silica can be improved by methylation. Over a catalyst with strong basicity, the Michael addition reaction of malononitrile with the double bond of 1,1-dicyanophenylethylene can proceed.…”

“…Nitridated MCM-48 were active catalysts for the Knoevenagel reactions between benzaldehyde and malononitrile. 172 The methyl group donates an electron to the nitrogen atom in silica frameworks, and thus enhances the basicity of nitridated SBA-15. Michael addition reaction is known to need stronger basic sites than Knoevenagel condensation.…”

MCM-41-Accelerated PWA Catalysis of Friedel-Crafts Reaction of Indoles and Isatins

“…And with the amount of catalyst reduced from 0.0050 g to 0.0030 g, the yield of the reaction was significantly decreased (Table 1, entries (16) and (17)). However, the amount of solvent obviously influenced the formation of the 3,3-di(indolyl)indolin-2-one and the best outcome was obtained with 0.3 mL THF at 0.1 mmol scale of isatin (Table 1, entry (18)). To our delight, the reaction time was slightly decreased to 2.5 h and could also successfully deliver the desired product in excellent yield up to 99% (Table 1, entry (19)).…”

“…In the last few years, ordered mesoporous siliceous material supporting catalysts have been paid much attention because of their high surface areas, large pores, and ordered arrangement of structures [18]. Phosphotungstic acid (PWA) supported on heterogeneous materials has been widely used for Friedel-Crafts reaction [19,20].…”

Hydrophobic Mesoporous Poly(ionic liquid)s towards Highly Efficient and Contamination‐Resistant Solid‐Base Catalysts

“…[22] Mesoporous solid bases are profitable because their high surface areas and large pore openings accelerate mass transfer by allowing bulky substrates to access the active sites. There have been numerous mesopo-rous solid basic catalysts appear in literatures, such as mesoporous magnesium oxide, [23] alkali ion exchanged hierarchical zeolites, [24] modified mesoporous silica, [25][26][27] mesoporous poly-(benzimidazole), and graphitic carbon nitride. [28,29] However, application of those currently available mesoporous solid bases faces with the conflict of activity and stability, that is, the more robust of the active sites, the higher the catalytic performance, but the easier poisoning of basic sites by moisture and/or CO 2 .…”