Preparation of L-Prolinamide Functionalized Mesoporous SBA-15 as Catalysts for Asymmetric Aldol Addition
Date Issued
2012
Date
2012
Author(s)
Chien, Chieh
Abstract
Prolinamide, prepared from proline and aromatic amine, has been found to be an efficient organocatalyst for asymmetric aldol reaction, which is a key carbon–carbon bond-forming reaction in nature and in the repertoire of the synthetic chemist. For the purpose of easy separation from the reaction mixture and reuses of the catalyst, prolinamide organocatalysts were immobilized on mesoporous silica by covalent bonding.
In the present study, thiol group functionalized SBA-15 ( SH-SBA-15 ) was prepared by one-pot co-condensation of tetraethyl orthosilicate ( TEOS ) and (3-mercartopropyl)trimethoxysilane ( MPTMS ) using P123 copolymer as surfactant in strong acidic environment. 4-O-allyl-hydroxyprolinamide prepared from trans-4-hydroxy-L-proline was modified with allyl group then linked with thiol groups by thiol-ene addition using Azobisisobutyronitrule ( AIBN ) as an initiator. Small-angle XRD patterns showed that the materials contained well-ordered mesopores arranged in 2-D hexagonal arrays. N2 sorption data showed their surface area, pore volume, and pore diameter decreased after prolinamide was immobilized. 29Si MAS NMR spectra confirmed that the organic silane is incorporated as a part of the silica wall structure. Sulfur K-edge XANES spectra showed the existence of C-S-C bond. 13C CP-MAS NMR spectra confirmed the existence of prolinamide structure. SEM and TEM images showed the morphology and mesoporosity did not change after prolinamide immobilization.
The immobilized catalysts were highly efficient in the asymmetric aldol reactions. The effects of solvents and different ketones reacting with 4-nitrobenzaldehyde were examined. The effect of mesostructure on the molecular diffusion during the heterogeneous catalytic reaction was studied.
Subjects
Prolinamide functionalization
Asymmetric aldol reaction
mesoporous silica.
Type
thesis
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