製備L-prolinamide官能基化的介孔SBA-15及其在不對稱Aldol加成反應的應用

Proline 及其衍生物 prolinamide 已被大量應用在不對稱 aldol 加成反應。在有機合成中，aldol 反應是生成碳-碳鍵最重要的方法之一，而不對稱的 aldol 反應是建構複雜的掌性醇體系結構的最有效的方法之一，其高選擇性在有機合成中已被大量應用在藥物及天然物的製備。異相觸媒具有容易從產物中分離、可以重複使用等優點。本研究將 prolinamide 的結構修飾成帶有 allyloxy 官能基，與帶有 thiol 官能基的介孔洞材料 SBA-15 ( SH-SBA-15 )，利用 AIBN 作為起始劑，進行 thiol-ene 自由基加成反應而可將 prolinamide 結構固定在介孔洞材料表面上，達到將 prolinamide 異相化的目的。有機光驅化合物 allyloxy-N-Boc-prolinamide 由 trans-4-hydroxy-L-proline 經一系列修飾而得；含硫醇官能基的介孔洞材料 SBA-15 乃由三區塊共聚物 ( P123 ) 作為模板試劑，將 tetraethyl orthosilicate (TEOS)、(3-mercartopropyl)trimethoxysilane ( MPTMS ) 在酸性環境下進行水解與共縮合反應，合成出具有不同外觀及不同孔道長度之含硫醇基的介孔洞材料 SBA-15。其 XRD 顯示孔洞具有良好排列的二維六角堆積結構。氮氣吸脫附恆溫曲線圖顯示材料的 BET 比表面積、孔洞體積、與孔徑在 allyloxy-prolinamide 鍵結在 SBA-15 材料表面上後有下降趨勢，顯示有機物存在孔洞中；硫的 K-edge 光譜圖顯示材料有 C-S-C 鍵的存在，顯示 allyloxy-prolinamide 與 SH-SBA-15 是以共價鍵鍵結；SEM 與 TEM 圖顯示材料的外觀與孔洞性不隨 prolinamide 的引入而改變。將含有 prolinamide 結構的 SBA-15 介孔洞材料觸媒應用在不對稱 aldol 加成反應，並藉由改變介孔洞材料其孔道長度、孔洞大小、催化反應溶劑、反應物的比例以及反應溫度等探討其觸媒反應活性。

關鍵字

介孔材料；不對稱合成

並列摘要

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.

並列關鍵字

Prolinamide functionalization ； Asymmetric aldol reaction ； mesoporous silica.

參考文獻

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製備L-prolinamide官能基化的介孔SBA-15及其在不對稱Aldol加成反應的應用

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