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

Abstract

Aldol reaction in water can effectively limit the formation of Schiff bases that deactivate active amine sites. To date, regulation of cooperative behaviors and morphologies of polymer-supported acid-base catalysts remains...

Colloidal polystyrene-supported cooperative imidazolidinone/thiourea catalysts for efficient aldol reaction and substrate-selective Knoevenagel condensation in water

“…Their average sizes determined by TEM ranged from ∼35 nm to ∼60 nm in diameter, and the sizes determined by DLS were significantly larger likely due to hydration, swelling, or/and aggregations of these nanoparticles in aqueous media. These findings are consistent with previous results, 28,36,37 indicating that nanoprecipitation is a powerful technique for the formation of colloidal polymer-supported molecular catalysts with controllable sizes and distributions. 29…”

“…2) were synthesized via the condensation (Scheme S6, ESI †) of 3,5-bis(trifluoromethyl)phenyl isothiocyanate with aminecontaining polystyrenes that were prepared and characterized in a previously reported work. 28 The successful preparation of PT1-4 was confirmed by 1 H NMR analysis (Fig. S9-S12, ESI †).…”

“…Recently, our groups developed a controllable approach for the preparation of polystyrene-supported acid–base catalysts. 28 Catechol-containing polystyrene and benzylamine-containing polystyrene were used as acid and base components for the formation of colloidal polystyrene in water by nanoprecipitation, 29 in which process the collapse of the hydrophobic polystyrene chains not only brought the acid and base in close proximity but also built hydrophobic microenvironments. 30 However, mutual deactivation between acid and base, the oxidation of catechol groups, and the poisoning of benzylamine groups through the formation of Schiff bases caused a significant loss of catalytic components, leading to moderate activities and recycling performance in the aldol reaction of 4-nitrobenzaldehyde with acetone in water.…”

“…Taken together, colloidal polystyrene-supported imidazolidinone/thiourea catalysts can more efficiently catalyze the aldol reaction in water compared to cooperative acid–base catalysts. 24,28…”

Recent advances in mixing-induced nanoprecipitation: from creating complex nanostructures to emerging applications beyond biomedicine

“…Similarly, PS-supported acid-base catalysts were prepared through nanoprecipitation to create a hydrophobic microenvironment and enable cooperativity between functional groups. 123 Taken together, nanoprecipitation allows easy access to a wide range of polymer-supported cooperative catalysis with superior catalytic performance. Fig.…”