"(1R,2R)-反式-1,2-二胺基環己烷衍生物官能基固定於介 孔材料SBA-15之特性分析及不對稱催化反應應用"

Abstract

近些日子，不對稱有機催化成為合成有機不對稱分子的一個嶄新方法。在西元2000年，L-脯氨酸在不對稱羥醛反應的發展與崛起，緊接著，原本用於不對稱配基之架橋的(1R,2R)-反式-1,2-二胺基環己烷，其衍生物在於不對稱有機催化劑上的應用，也開始著手進行調查。不過，在有機催化上，有機催化劑的不易合成，與其較低的催化活性，以及與不對稱產物分離困難等課題，仍急需被克服。藉此，此論文的主要目的即針對(1R,2R)-反式-1,2-二胺基環己烷及其衍生物固定於介孔材料SBA-15為主軸，以此系統探討介孔材料對於有機不對稱催化反應之影響，並更進一步克服及達成與產物分離步驟簡單和催化劑重複使用的理想。 在(1R,2R)-反式-1,2-二胺基環己烷之衍生物，一級-三級二胺基環己烷固定於SBA-15方面，我們發現到藉由孔壁表面的矽羥基影響，當以強酸為助催化劑時，環己酮對4-硝基苯甲醛的不對稱羥醛反應會產生與固定前完全相反的位向選擇，再以具氫建且環境保護的水為溶劑時，可以降低孔壁表面矽羥基的影響，進而達到不需要酸為助催化劑，即可催化此不對稱羥醛反應。 在含有(1R,2R)-反式-1,2-二胺基環己烷之尿素衍生物固定在SBA-15方面研究，我們發現到以有機鹼為助催化劑時，對於不對稱Michael加成反應有良好的催化活性，更進一步，利用改變反應物取代基的立體障礙，達到良好的位向選擇。

The main purpose of this thesis is to optimize the structure of hybrid mesoporous silica, SBA-15, containing (1R,2R)-trans-1,2-diaminocyclohexane-fragments on their surface in order to develop efficient organocatalytic solid materials. For the synthesis of such materials, some improvement of the sol-gel and post-functionalization techniques will be required.The main results of this dissertation can be summarized as follows. In the main part I, the entirely different catalytic results were discovered after immobilizing primary-tertiary chiral diamine in SBA-15 for the direct asymmetric aldol reaction of cyclohexanone with aryl aldehyde. Besides, water was found to be a suitable reaction medium for these reactions with relatively low amounts of supported diamine catalysts and in the absence of the acid co-catalyst. Moreover, (1R,2R)-trans-1,2-diaminocyclohexane-hexanedioic acid-SBA-15 has been demonstrated to catalyze the asymmetric aldol reaction of cycloketone and isatin efficiently in MeOH-H2O. The corresponding products were obtained in good conversion (up to 99%) with high enantioselectivity (up to 93% ee). In the main part II, the chiral ureas derived from (1R,2R)-trans-1,2-diaminocyclohexane were prepared and immobilizedon SBA-15. It was found to be highly effective heterogeneous catalysts for the conjugate addition of isobutyraldehyde to nitrostyrene with base co-catalyst. The base additives are essential for good efficiencies in this transformation. In addition, chiral primary amine urea-SBA-15 catalysts were successfully applied to promote Michael addition of isobutyraldehyde to maleimide. The N-aryl maleimide provided Michael adducts in excellent enantioselectivity (up to 90% ee) with 10 mol % catalyst.