Readily accessible mesoporous silica nanoparticles supported chiral urea‐amine bifunctional catalysts for enantioselective reactions

Abstract

The main objective of this study is to develop readily accessible and recyclable solid catalysts for enantioselective reactions. To achieve this, magnetic MCM‐41 and non‐magnetic SBA‐15 mesoporous supports were prepared, then mesoporous silica supported chiral urea‐amine bifunctional catalysts were synthesized by grafting of chiral urea‐amine ligand onto SBA‐15 and magnetic MCM‐41. The magnetic and non‐magnetic supports and so‐prepared solid catalysts were characterized by using different methods such as N2 sorption measurements, Fourier transform infrared spectroscopy (FT‐IR), field emission scanning electron microscope‐energy dispersive X‐ray analysis (FESEM‐EDX), X‐ray diffraction (XRD), and thermogravimetric analysis (TGA). Results showed that (1R, 2R) or (1S, 2S)‐1,2‐diphenylethane‐1,2‐diamine was successively immobilized onto magnetic MCM‐41 and SBA‐15 pores. The heterogeneous chiral solid catalysts and their homogenous counterparts exhibited high activities both enantioselective transfer hydrogenation reaction (up to 99% conversion and 65% ee) and enantioselective Michael reaction (up to 98% conversion and 26% ee). Moreover, the SBA‐15 supported solid catalysts were separated from the reaction mixture by simple filtration, whereas the magnetic MCM‐41 supported solid catalysts were separated by simple magnetic decantation and reused in three consecutive catalytic experiments.

pH responsive curcumin released from urea-amine group functionalized mesoporous organosilica nanoparticles

“…The urea-amine ligand 1 and reference material MCM-41 were synthesized by following the method given in the literature [ 27 , 28 ]. Cetyltrimethylammonium bromide (CTAB), tetraethylortosilicate (TEOS), curcumin, and all the other materials were purchased from commercial suppliers (Merck or Sigma-Aldrich).…”

Application of chiral recyclable catalysts in asymmetric catalysis

“…These catalysts, referred to as 38 (7 mol%) (Scheme 38). 127 demonstrated remarkable activity in transfer hydrogenation (achieving a yields of up to 99% and an ee of 65%) and enantioselective Michael reaction (achieving a yields of up to 98% and an ee of 26%). The solid catalyst loaded on SBA-15 ( 38c / 38d ) can be easily separated by filtration, while the solid catalyst loaded on magnetic MCM-41 ( 38e / 38f ) can be separated and reused for up to 3 cycles through simple magnetic precipitation.…”

Study on the relationship of catalytic activities and o‐Ps annihilation properties of supported palladium species chelated by different functional groups

“…Mesoporous materials have been widely studied and applied in catalysis for their unique long-range ordered hexagonal symmetric channel structure and large surface area. [26][27][28][29][30] Herein, by reacting with APS and then nine substituted aromatic aldehydes, MCM materials were chemically modified with nine functional groups as the supports of Pd 2+ cations. The functional groups on the MCM-41 were confirmed by FT-IR spectra (Figures 1, S1, and S2).…”