"以(1R,2R)-反式-1,2-二胺基環己烷衍生物官能基化介孔材料SBA-15催化不對稱Aldol反應之應用"

Abstract

本篇論文將具有掌性選擇之(1R,2R)-trans-1,2-diaminocyclohexane固定在介孔材料SBA-15上而製備出一級-三級胺以及二級-三級胺兩種掌性選擇催化劑，以NMR、XRD、氮氣吸脫附、熱重分析等方式鑑定，並應用於不對稱Aldol反應。本實驗中，利用對硝基苯甲醛與環己酮作為反應物進行不對稱Aldol反應，比較兩種掌性選擇催化劑之活性，並與勻相觸媒比較。本研究亦探討不同取代基之苯甲醛衍生物在兩種觸媒上進行Aldol反應的差異與可能的反應過渡態。 本研究發現以對硝基苯甲醛與環己酮作為反應物的不對稱Aldol反應之中，SBA-15固定化之一級-三級胺觸媒可以在有水的環境下得到高達96%的轉化率以及很高的反式產物(anti-isomers)立體選擇性，遠超過二級-三級胺的50%轉化率。因此本論文主要以SBA-15固定化之一級-三級胺觸媒來進行反應物之間各種不同參數的探討，包含了利用數種質子與非質子溶劑測試最佳反應溶劑、作為溶劑的水量多寡對催化表現造成的影響、在各種不同溶劑中添加三氟乙酸帶來的高選擇性、一級-三級胺在無水的環境下若以微量的三氟乙酸做為添加劑會將立體選擇性逆轉，本逆轉現象也以重複回收使用觸媒驗證 在本研究的最後，我們也利用許多帶有不同程度之推、拉電子基與大小取代基之苯甲醛衍生物對Aldol反應過渡態的影響與其最後產生的產物分布進行探討，推論出取代基之位置、大小與推拉電子特性對一級-三級胺觸媒催化表現之影響；同時也將觸媒用在不同種酮類上推廣觸媒的應用範圍。

In this work, (1R,2R)-trans-1,2-diaminocyclohexane was grafted on mesoporous SBA-15 through either thio-ene addition or by substitution to generate a enantio-selective primary-tertiary or secondary-tertiary amine catalyst, respectively. These chiral selective catalysts were characterized by NMR, X-ray diffraction, N2 adsorption-desorption isotherm, and thermogravimetric analysis. These two enantio-selective catalysts were tested in asymmetric aldol reaction with p-nitrobenzaldehyde and cyclohexanone. The catalytic activities were also compared with the homogeneous one. The effect of using benzaldehyde derivatives with different substituents in the aldol reactions was examined and the possible transition states were also proposed. The experimental results demonstrated that a higher conversion up to 96% and higher stereo-selectivities were obtained in the presence of water over immobilized primary-tertiary amine catalyst than the 50% conversion over the secondary-tertiary amine catalyst. Hence, the primary-tertiary amine catalyst was the focus in this thesis for studying the effect of different parameters, including the protic and aprotic solvents, amount of water used as the solvent, and acid additives, alternation of stereo-selecticity with catalytic TFA under neat condition. The phenomenon of alternation was also examined by recycling test. In the last part, the effect of various substituents on benzaldehyde of different electron-withdrawing/donating strengths and sizes on the transition state and distribution of products in catalytic asymmetric aldol reaction over SBA-15 immobilized primary-tertiary amine catalyst are discussed. Different ketones as another reactant were also investigated to extend the application of this catalyst.