Recyclable Merrifield resin-supported thiourea organocatalysts derived from l-proline for direct asymmetric aldol reaction

Nanoparticle Based on Poly(Ionic Liquid) as an Efficient Solid Immobilization Catalyst for Aldol Reaction and Multicomponent Reaction in Water

An environmentally friendly nanoparticle-supported catalyst was successfully prepared via in situ ionic complexation between imidazolium-based polymer ionic liquid (PIL) and poly(l-prolinamide-co-MAA). The physical and chemical properties of the obtained nanoparticles were characterized by TEM, FTIR, XPS, and static water contact angle experiments. The surface properties of the nanoparticle were found to significantly affect the catalytic performance. The nanoparticle with PIL outer facilitated the adsorption of reaction substrate in it. As a result, the catalytic system catalyzed the asymmetric Aldol reaction and multicomponent reaction in pure water efficiently. The catalytic system was able to be reused and recycled five times, and with no discernible loss in catalytic activity and enantioselectivity. These findings suggest that nanoparticles based on PIL may provide a new approach for preparing high performance supported catalysts for organic reactions in water. This technology also addresses issues associated with mass transfer in pure water reactions.

Supported bifunctional thioureas as recoverable and reusable catalysts for enantioselective nitro-Michael reactions

The catalytic activity of different supported bifunctional thioureas on sulfonylpolystyrene resins has been studied in the nitro-Michael addition of different nucleophiles to trans-β-nitrostyrene derivatives. The activity of the catalysts depends on the length of the tether linking the chiral thiourea to the polymer. The best results were obtained with the thiourea derived from (L)-valine and 1,6-hexanediamine. The catalysts can be used in only 2 mol % loading, and reused for at least four cycles in neat conditions. The ball milling promoted additions also worked very well.

Aminoalkylated Merrifield Resins Reticulated by Tris-(2-chloroethyl) Phosphate for Cadmium, Copper, and Iron (II) Extraction

We aimed to synthesize novel substituted polymers bearing functional groups to chelate heavy metals during depollution applications. Three polyamine functionalized Merrifield resins were prepared via ethylenediamine (EDA), diethylenetriamine (DETA), and triethylenetetramine (TETA) modifications named, respectively, MR-EDA, MR-DETA, and MR-TETA. The aminoalkylated polymers were subsequently reticulated by tris-(2-chloroethyl) phosphate (TCEP) to obtain new polymeric resins called, respectively, MR-EDA-TCEP, MR-DETA-TCEP, and MR-TETA-TCEP. The obtained resins were characterized via attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), elemental analysis (EA), and thermogravimetric (TGA), thermodynamic (DTA), and differential thermogravimetric (DTG) analysis. The synthesized resins were then assayed to evaluate their efficiency to extract metallic ions such as Cd2+, Cu2+, and Fe2+from aqueous solutions.

A novel poly(N-isopropyl-acrylamine-co-l-proline) catalyst for aldol reaction: synthesis, catalytic performance and recyclability

A novel homogeneous copolymer catalyst, poly(N-isopropyl-acrylamine-co-l-proline), possesses excellent activity and stereoselectivities. Even after ten cycles, the catalytic activity and stereoselectivities remained almost unchanged. The circular dichroism spectra of the copolymer catalyst are apparently different from the corresponding monomer.

The smallest organocatalyst in highly enantioselective direct aldol reaction in wet solvent-free conditions

The catalytic efficacy of the smallest organocatalyst, l-proline hydrazide, prepared from a cheaply available natural amino acid, such as l-proline, was studied for the direct asymmetric aldol reaction of various ketones with aromatic aldehydes at room temperature in the presence of several acid additives.

An efficient solvent-free synthesis of 2-hydroxy-2-(trifluoromethyl)-2H-chromenes using silica-immobilized L-proline

An efficient synthesis of 2-hydroxy-2-(trifluoromethyl)-2H-chromene-3-carboxylates was carried out under solvent-free conditions in an oven or microwave oven via the Knoevenagel condensation of salicylaldehydes with ethyl trifluoroacetoacetate followed by intramolecular cyclization in the presence of silica-immobilized L-proline. The structures of the title compounds were characterized by IR, ¹H-NMR, ¹³C-NMR, HRMS and X-ray single crystal diffraction. The improved method described herein is economical, easily-operated and environmentally friendly. Furthermore, the catalyst can be recovered conveniently and reused without obvious loss of activity.