The role of metallic modifiers of SBA-15 supports for propyl-amines on activity and selectivity in the Knoevenagel reactions

Current advances in the utility of functionalized SBA mesoporous silica for developing encapsulated nanocatalysts: state of the art

“…One of the most important advances in this eld is developing hybrid systems through functionalization of mesoporous silica materials. [51][52][53][54][55][56] In this context using sulfur, [57][58][59][60][61][62] phosphorous and amine-based functional groups 63,64 has attracted growing attention and resulted in introducing novel hybrid systems [65][66][67][68] with outstanding utilities for catalysis.…”

Nb2O5/SBA-15 catalyzed propanoic acid esterification

“…Nb/SBA-15 has been explored by Calvino-Casilda et al who studied the impact of Zr, Nb and Mo modified SBA-15 in Knoevenagel condensation, along with a series of bifunctional materials based on modified SBA-15 co-functionalized by aminopropyl groups. Nb/SBA-15 co-functionalised with propylamine groups showed the highest activity, which was attributed to a strong interaction between Nb cations and the silica support generating Lewis acidity [26,27]. Nb/SBA-15 has also been prepared in the presence of grafted propylsulfonic acid groups for use in glycerol esterification with acetic acid, in which Nb appeared to improve the stability of sulfonic acid functions, resulting in 66 % glycerol conversion and 35 % selectivity to triacetylglycerol [28,29].…”

An Efficient and Reusable Multifunctional Composite Magnetic Nanocatalyst for Knoevenagel Condensation

“…Even aryl aldehydes bearing strongly electron-withdrawing nitro or carboxy groups reacted readily and efficiently to afford the desired products in excellent yields (SI; Table S2, entries 6 and 7). Note that the reaction rates of ketones were slower than those of aldehydes and that longer reaction times were needed to obtain good to excellent yields (SI; Table S2, entries [11][12][13][14][15][16][17]. It is also interesting to note that the reaction of malononitrile with hexane-2,5-dione (SI; Table S2, entries 14 and 15) gave the dicondensation product 2,5-dimethylhexa-1,5-diene-1,1,6,6-tetracarbonitrile exclusively, whereas pentane-2,4-dione gave the monocondensation product (1-methyl-3-oxobutylidene)malononitrile (Table S2, entry 16).…”

“…In this regard, a number of representative heterogeneous catalysts have been developed for the Knoevenagel condensation, including phosphotungstic acid immobilized on mesoporous graphitic carbon nitride (g-C 3 N 4 ), 4 Ni/SiO 2 , 5 g-C 3 N 4 , 6 aziridine-functionalized multiwalled carbon nanotubes, 7 triethylenetetramine-functionalized polyacryloni-trile fiber, 8 rhodium-platinum nanoparticles supported on thiocarbamide-functionalized graphene oxide, 9 a core-shell silica-layered double hydroxide, 10 ionic liquids, [11][12][13] and others. [14][15][16][17][18] Most of these catalysts are efficient but, nevertheless, suffer from various limitations, such as a relative lack of availability or environmental contamination. Therefore, the development of more-sustainable and more-efficient catalysts for the Knoevenagel condensation continues to be a challenging goal.…”