Aminated poly(ethylene glycol) methacrylate resins as stable heterogeneous catalysts for the aldol reaction in water

Engineering of polystyrene-supported acid–base catalysts for aldol condensation in water

“…In contrast, the increase in local concentration of the functional groups caused a decline in catalytic activity, likely accounting for the decrease in the number of active sites that might be destroyed by the formation of protonated amines and/or Schiff bases within nanoparticles. 15,25 The highest TOF (1.56 h −1 ) was obtained when PA3 and PC1 were used for the preparation of nanoparticle catalysts, comparable to that of reported silica-supported catalysts and polymer-supported catalysts (Table 2). Taken together, catalytic activity could be easily regulated by using various benzylamine-containing copolymers and catechol-containing copolymers for the preparation of nanoparticle catalysts via the nanoprecipitation technique.…”

“…25 Because a low polarity microenvironment destabilizes protonated amines, and water inhibits the formation of Schiff bases. 15 The coil-globule collapse of polymer chains can efficiently achieve such combination, decreasing the extent of deactivation. In contrast to the precise spatial arrangement of functional groups of enzymes, spatial cooperation between benzylamine and catechol is realized by statistical distributions inside nanoparticles.…”

“…To overcome this limitation, organic support materials, especially polymers, are promising alternatives to silica-based materials for more hydrothermally stable heterogeneous catalysts in aqueous reactions. Amine-functionalized polymers such as polystyrene, 17 poly(ethylene glycol), 15 chitosan, 18 and cellulose nanocrystal 19 have been synthesized and used as catalysts for aldol reaction in aqueous solutions. 20 To promote catalytic performance, neighboring hydroxyl or carboxylic acid groups were integrated into catalysts to achieve cooperative acid–base catalysis.…”

“…Water has been considered as a green solvent for organic reactions because it is nontoxic, uninflammable, cheap, and readily available. 13,14 However, amine-functionalized silica materials are unstable in water because of the hydrolysis of silica under alkaline conditions caused by amine groups, 15,16 limiting their longterm use in aqueous solutions.…”

Critical Assessment of the Thermodynamics in Acidic Resin-Catalyzed Esterifications

“…Cross-linked polymer resins, either unmodified or functionalized with specific groups, are used in a broad range of applications, including, among others, water treatment, chromatography, hydrogen storage, and hydrometallurgy. − Additionally, functionalized resins are increasingly used as high-performance heterogeneous catalysts for organic synthesis reactions, such as (trans)­esterifications, etherifications, dehydrations, aldol reactions, Suzuki–Miyaura cross-couplings, phenol alkylations, and so forth. − It should, however, be noted that these materials exhibit a remarkable phenomenon as compared to other types of heterogeneous catalysts. Namely, when a dry resin is allowed to make contact with a liquid, it tends to swell, that is, a portion of the liquid is sorbed by the resin, resulting in an increase of its volume. ,,− The sorption phenomena occurring during the swelling of a resin can be classified into two categories: (i) absorption of liquid into the resin pores and (ii) adsorption of components onto functional groups.…”