樟腦分子衍生物之硼氮氧環化物之製備及在酮類化合物還原反應之應用

Preparation of Camphor-Derived Oxazaborolidines and the Application to Reduction of Ketones

沈建宏(Chien-Hung Shen)

指導教授 ： 徐基東

朝陽科技大學/理工學院/應用化學系/碩士(2009年)

摘要

為了得到高效率與高立體選擇性的硼烷掌性輔助劑 (Oxazaboro- lidines)，以便用於酮類化合物的還原反應，我們使用便宜且容易取得的天然物樟腦分子為起始物，合成新型的Oxazaborolidines。首先，我們以製備了以樟腦分子為架構的醛基[2.2.1]雙環三級醇化合物。接著，此三級醇化合物與一級胺分子反應產生擴環之[3.2.1]雙環胺基酮衍生物。
然後，此胺基酮衍生物分子內的酮基被還原為醇基而形成進行還原反應成[3.2.1]雙環胺基醇產物，即1,2-胺基醇衍生物。之後，再使此一胺基醇衍生物與硼烷或硼酸烷反應，生成[3.2.1]雙環氮氧硼狀產物(Oxazaborolidines)。最後，這些Oxazaborolidines 當作具有鏡像選擇功能之還原反應催化劑，應用在不對稱酮類分子的還原反應，此還原反應的產物即是具立體中心之二級醇化合物。而在最佳的實驗狀況（10 mol% catalyst, THF, r.t）下，二級醇產物之產率可達到90 %，且鏡像超越值（
% ee）達到99 ％ 以上。

關鍵字

樟腦 ； 不對稱還原反應 ； 硼氮氧環化物

並列摘要

In order to obtain an excellent and cheaper chiral ligand for borane
reduction, we have synthesized some new oxazaborolidines, starting from camphor, which is an inexpensive and readily available natural product. At first, the camphor-derived formyl [2.2.1]bicyclic carbinol was prepared. Then, the reaction of the bicyclic carbinol with some primary amines provided regio-specific [3.2.1]bicyclic amino ketones. Treatment of bicyclic amino ketones with sodium borohydride produced stereospecific [3.2.1]bicyclic amino alcohol. The separate reactions of boroxine and borane with [3.2.1]bicyclic amino alcohol, then, afforded new oxazaborolidines, which were immediately used as chiral auxiliaries for the asymmetric reduction of some prochiral ketones to give stereospecific secondary alcohols. The secondary alcohols were obtained in 85 ~ 97 % yield with >99 % ee under the best reduction conditions.

並列關鍵字

oxazaborolidine ； camphor

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