Organocatalyst Derived 4-(Dimethylamino)pyridine for the Kinetic Resolution of Racemates and meso-Compounds
動力學分割 ； Kinetic Resolution
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4-二甲胺基吡啶常作為親核性試劑催化各類反應，近年來，有許多科學家開發出以4-二甲胺基吡啶為架構的掌性催化劑並應用在動力學分割及去對稱化上有不錯的成果。本實驗室以掌性4-二甲胺基吡啶之有機催化劑進行動力學分割反應期望達到良好的產率及鏡像選擇性。 本篇論文結合樟腦架構與4-二甲胺基吡啶設計合成新穎有機催化劑91。首先，以催化劑91進行內消旋二醇去對稱化反應及動態動力學分割氮代內酯反應，可惜的是，並沒有達到預期的結果。接著，嘗試進行動力學分割二級醇的反應。所選用的起始物為2-羥基羧酸酯及乙酸酐(0.8當量)，以甲苯為溶劑並添加催化劑91 (20 mol%)和N, N-二異丙基乙胺在-75 oC下為最佳反應條件，可得到產物的鏡像超越值為16%，回收起始物之鏡像超越值為88%。而起始物及產物的絕對立體組態仍待鑑定。
4-(Dimethylamino)pyridine (DMAP) is one of the most frequently used nucleophilic catalysts. Recently, chiral 4-(dimethyl)aminopyridine derivatives have been extensively used as potent nucleophilic catalysts in kinetic resolution and desymmetrization. We are interested in using chiral 4-(dimethylamino)pyridine derivatived organocatalysts in kinetic resolution to get high chemical yield and enantioselective excess. In addition, the new types of organocatalysts 91 combining camphor and 4-(dimethyl)aminopyridine has also been designed and prepared. First, the new organocatalyst was used as a catalyst for desymmetrization of meso-1,2-diols and dynamic kinetic resolution of azalactones. Unfortunately, our results showed that only rather low enantioselectivity was obtained with this catalyst system. Next, We have also studied the kinetic resolution of secondary alcohols. The reaction was carried out under -75 oC by using the 2-hydroxyalkanoates and acetic anhydride (0.8 equiv) as the starting materials in toluene in the presence of catalyst 91 (20 mol%) and N,N-diisopropylethylamine. The ee value of the 2-acyloxyalkanoates is 16% ee and The ee value of the 2-hydroxyalkanoates can be up to 88% ee. However, the major enantiomer was not determination.
理學院 > 化學系