Hybrid Inorganic‐Organic Materials Carrying Tertiary Amine and Thiourea Residues Tethered on Mesoporous Silica Nanoparticles: Synthesis, Characterization, and Co‐Operative Catalysis

Abstract

Mesoporous silica nanoparticles carrying different loadings of tertiary amine and thiourea residues (residues ratios 53/47, 68/32, and 22/78, respectively) were synthesized by the co-condensation method and fully characterized by CP MAS NMR, powder XRD, SEM, BET, BJH and FT-IR techniques. These materials were tested as bifunctional catalysts in the conjugate addition of acetylacetone to 2-nitrostyrene, a reaction that under solvent-free conditions occurred in quantitative yield. By carrying out several experiments with the bifunctional catalysts featuring different molar ratios of active sites, and with different combinations of monofunctional supported and non-supported catalyst, the co-operativity of the tertiary amine and thiourea residues in catalyzing the reaction was demonstrated. The use of the bifunctional catalyst was extended to the addition of acetylacetone to an activated imine. Catalyst recycling for a total of three reaction cycles was demonstrated without significant erosion of activity.

Recyclable organocatalysts based on hybrid silicas

“…95,96 Later on, inspired by the structure of the Takemoto catalyst, Puglisi et al designed a catalytic material containing bis(trifluoromethyl)phenylthiourea and tertiary amine functions, that were shown to work hand-in hand during the catalytic Michael addition of acetylacetone on nitrostyrene. 97 Randomly-distributed independent functions can also be implemented through click reactions from a single parent material. 98,99 This approach was recently developed by the group of Studer, with the synthesis of materials featuring both azide and alkene, or azide and alkoxyamine functions.…”

Adsorptive removal of dihydrogenphosphate ion from aqueous solutions using mono, di- and tri-ammonium-functionalized SBA-15

“…Therefore, organic functional groups such as amine, thiol, carboxylic, alkyl chloride, and aromatic have been incorporated into the structure of mesoporous material via post-synthesis grafting or co-condensation. Among all these organic functional groups, several investigations were dedicated to surface modification of different mesoporous silicas using aminoalkoxysilanes for their application in catalysis [2,[6][7][8] as well as environmental pollution control [9][10][11][12][13][14][15][16]. In this regard, different amino-functional groups including mono-, di-and tri-amines proved to be potent adsorbents for heavy metal cations such as mercury, lead, cobalt, copper and zinc cations from water [9,[17][18][19], organic molecules [20,21] as well as CO 2 from gaseous emissions [22][23][24].…”

Comparison of Different Polymer‐ and Silica‐Supported 9‐Amino‐9‐deoxy‐epi‐quinines as Recyclable Organocatalysts

“…[22] However,n oi mprovements were obtained (Table 4). [22] However,n oi mprovements were obtained (Table 4).…”

“…In an attempt to circumventt he problem of the diminished chemicaly ields, catalyst PS-QNc was dried under vacuum at 80 8Cb efore use, to eliminate possible impurities trapped in the porous structure. [22] However,n oi mprovements were obtained (Table 4).…”