Functionalized Core–Shell Polystyrene Sphere-Supported Alkaline Imidazolium Ionic Liquid: An Efficient and Recyclable Catalyst for Knoevenagel Condensation

Abstract

A supported alkaline imidazolium ionic liquid catalyst with an ionic liquid shell and polystyrene core was synthesized. The core−shell structure was achieved by swelling polymerization of 4-vinylbenzyl chloride and divinylbenzene around polystyrene particles followed by quaternization reaction with 1-propyl-1H-imidazole and ion exchange. The results obtained from FTIR, SEM, TEM, TGA, DLS, and elemental analysis indicated that the ionic liquid shell was successfully coated on polystyrene spheres. The core−shell catalyst displayed excellent activity and solvent tolerance for Knoevenagel condensation of benzaldehyde with ethyl cyanoacetate because of its good dispersion, low mass-transfer resistance, and good swelling property. Meanwhile, it exhibited superb stability and recyclability, benefitting from the active species being anchored to the highly cross-linked polymer carrier. The catalyst was reused 10 times in water or methanol without significant change in catalytic activity, composition, and microstructure. Moreover, the catalytic performance of the prepared catalyst was weakened by the increased masstransfer resistance with the movement of active sites from the surface to the interior of the carrier.

Organoamine Templated Multifunctional Hybrid Metal Phosphonate Frameworks: Promising Candidates for Tailoring Electrochemical Behaviors and Size-Selective Efficient Heterogeneous Lewis Acid Catalysis

“…The interest toward the Lewis acid-based heterogeneous catalytic reaction has been extensively increasing as it offers several advantages such as simple separation, easy way of functionalization, better recyclability, and eco-friendly nature of the catalyst. 40,42,43 To date, various kinds of heterogeneous catalytic reactions such as cyanosilylation, 44,45 Knoevenagel condensation, 46 Friedel−Crafts alkylation, 47 and the tandem reaction 48 have been explored, but the popular ketalization reaction has rarely been investigated. The ketalization reaction is one of the most fundamental and viable methods for protecting carbonyl groups during several organic transformation reactions and is often catalyzed by the presence of Lewis acids.…”

Understanding the Ingenious Dual Role-Playing of CO2 in One-Pot Pressure-Swing Synthesis of Linear Carbonate

“…Primarily, Fourier transform infrared (FT-IR) spectra of the catalysts are depicted in Figure a, reflecting the successful introduction of functional groups within the polymeric framework. The characteristic peaks of the benzene ring could be clearly observed from the stretching vibration of C–H at 3000–3100 cm –1 and the skeleton vibration of CC at 1600 cm –1 in all samples . The peaks at 1160 cm –1 corresponded to the stretching vibration of C–N + in PIL samples, indicating that imidazolium cations had been successfully quaternized .…”

“…The characteristic peaks of the benzene ring could be clearly observed from the stretching vibration of C−H at 3000−3100 cm −1 and the skeleton vibration of CC at 1600 cm −1 in all samples. 27 The peaks at 1160 cm −1 corresponded to the stretching vibration of C−N + in PIL samples, indicating that imidazolium cations had been successfully quaternized. 28 The C−O stretching vibration peaks of anionic phenolic hydroxyl groups appeared at 1230 cm −1 in P-DAEImPh and P-DAEImOPy (Figure S4).…”

Highly Active Cyclic Zinc(II) Thione Catalyst for C−C and C−N Bond Formation Reactions

“…The classic C−C double bond‐forming reaction such as the Knoevenagel condensation reaction has been extensively employed for the synthesis of fine chemicals for materials and medicinal applications [1–4] . Many synthetic methodologies have been developed using a variety of catalysts, including ionic liquids, [5] organocatalysts, [6] metal‐based catalysts such as Lewis acids, Lewis acid‐base pairs, [7a,b] MOFs, [8] and various nanocatalysts [9] . However, metal‐based catalysts have several limitations due to environmental toxicity, selectivity, sustainability, elevated temperature, longer reaction time, limited substrate scope, and uses of additives.…”