Preparation of L-Proline Functionalized SBA-15 as Catalysts for Asymmetric Aldol Addition
Date Issued
2010
Date
2010
Author(s)
Yang, Chia-Ming
Abstract
L-Proline is known as an organocatalyst for asymmetric Aldol reaction. For the purpose of easy separation and reuse of the catalyst, L-proline was immobilized onto mesoporous silica to form heterogeneous catalyst through thiol-ene addition using AIBN as the initiator. Cis-4-mercapto-L- proline (SH-proline) was synthesized from trans-4-hydroxy-L-proline. Vinyl group functionalized SBA-15 (briefly termed vinyl-SBA-15) was prepared by co-condensation of tetraethyl orthosili- cate (TEOS) and vinyltrimethoxysilane (VTMS) using P123 copolymer as the pore directing agent in strong acidic environment. 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 L-proline was immobilized. Sulfur K-edge XANES spectra showed the existence of C-S-C bond. 13C CP/MAS solid state NMR showed the existence of proline structure. SEM and TEM images showed the morphologies and mesoporosity didn’t change after poline was immobilized. The SBA-15 immobilized L-proline materials were used as catalysts in the asymmetric Aldol reaction. The pH value of pre-treatment solution, reaction solvent, and temperature were found to affect the chiral selectivity drastically.
Subjects
proline
asymmetric
heterogeneous
SBA-15
Aldol
Type
thesis
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