含掌性Proline衍生物之介孔SBA-15分子篩的合成與應用

Chiral Proline Derivative Anchored on Mesoporous SBA-15 Silica：Synthesis and Application

蕭麗秀(Li-Hsiu Hsiao)

指導教授 ： 鄭淑芬

國立臺灣大學/理學院/化學研究所/碩士(2006年)

https://doi.org/10.6342/NTU.2006.10452

摘要

本論文主要利用介孔材料的具規則孔洞及高表面積之特性，將掌性觸媒均勻固定到介孔材料的孔壁上，以得到可重複使用的掌性觸媒材料。實驗方法上，在酸性條件下，以EO20PO70EO20 (P123)作為模版試劑，TEOS及CPTMS作為矽源，經由共縮合法 (co-condensation)一步合成或利用後嫁接法製備出含氯丙基的介孔SBA-15分子篩。接著再經過親核取代反應，將氯取代成掌性Proline衍生物(α,α-Diphenyl-L-prolinol)。所得到的觸媒經由X-光粉末繞射、固態核磁共振、元素分析等的鑑定，得知其結構及掌性官能基的含量，並進一步應用在二乙基鋅對苯甲醛的不對稱催化反應上。
在二乙基鋅對苯甲醛的不對稱催化反應方面，結果顯示修飾掌性Proline衍生物的SBA-15，其Proline衍生物的分布及Proline衍生物的含量對於鏡像選擇能力的影響極大，其中含15%氯丙基的SBA-15，由於其所含的鏡像輔助劑的量是最多的，分布也較均勻，所以相較於其他含量的氯丙基，其催化活性最佳，最高可以達到 66% 的鏡像超越值。而改變孔洞內活性位置周圍的親疏水性質，則可以改變反應速率，由實驗結果顯示在活性中心周圍修飾甲基官能基可以加速反應的進行。另外在反應中加入 n-BuLi 則可將鏡像超越值提高至75% e.e.。最後將反應過的材料再生利用，鏡像選擇性與反應速率都能維持一定的水準。

關鍵字

介孔SBA-15 ； Proline衍生物 ； 掌性

並列摘要

Mesoporous SBA-15 silica materials were functionalized with chloropropyl group either through co-condensation of tetraethyl orthosilicate (TEOS) and (3-chloropropyl)-trimethoxysilane (CPTMS) in the presence of triblock copolymer P123 as structure directing agent under acidic condition or by grafting calcined SBA-15 silica with CPTMS. The chloropropyl groups were then converted to chiral proline derivative (α,α-Diphenyl-L-prolinol) through nucleophilic substitution with proline derivative. The resultant materials were characterized by various techniques including X-ray powder diffraction, solid state NMR, elemental analysis to verify the structure and chemical composition. These functionalized materials were applied to asymmetric diethylzinc addition to benzaldehyde as chiral selective catalysts.
The enantioselectivity of 1-phenyl-propanol was found to be markedly dependent on the amount and the distribution of the prolinol groups inside the mesopores. High enantiometric excess 66% e.e. was achieved when 15%Cl-tolu-cata was used as the chiral catalyst. In addition, better enantiometric excess of 75% was obtained if n-BuLi was also added in the reaction. The reaction rate was also influenced by the hydrophobic environment around the active sites and the reaction rate increased when the walls of mesoporous silica were functionalized with methyl groups. Finally, the enantioselectivity and reaction rate were found to retain when the used catalysts were reused.

並列關鍵字

mesoporous SBA-15 ； proline derivative ； chiral

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