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  • 學位論文

四組份合成之有機鏻鹽在替代兩雜環耦合反應之應用 新型全碳 1,3-偶極體前驅物 3-Homoacyl Coumarin 用於鏡像選擇性 (3+2) 協同環化反應合成 Herbertenolide 衍生物之應用

Four-component Synthesis of Phosphonium Salts: Application toward an Alternative Approach to Cross-coupling for the Synthesis of bis-Heteroarenes 3-Homoacyl Coumarins as a Class of All-Carbon 1,3-Dipole Precursor: An Enantioselective Concerted (3+2) Cycloaddition towards Herbertenolide Derivatives

指導教授 : 林文偉

摘要


第一章 四組份合成之有機鏻鹽在替代兩雜環耦合反應之應用 近年來,有機磷化物已被大量的使用在工業及實驗室之中,其中有機鏻鹽亦是重要的磷化物之一。有機鏻鹽的獨特性質讓其不只可以作為離子液體或是相轉移催化劑來輔助反應進行,更常見的是作為Wittig 反應的重要試劑。敝實驗室長期著墨在發展 Wittig 反應,直至目前為止已開發出兩類有機鏻鹽 Wittig 試劑的合成策略用以經由分子內 Wittig 反應合成不同的雜環分子。我們期望可以探索出新穎的可純化之穩定鏻鹽的合成策略,並利用此有機鏻鹽進行分子內 Wittig 反應來合成不同於以往的雜環分子。 在本章節中,我們成功的開發了一種四組份反應合成一系列可單離的穩定有機鏻鹽,並可藉由不同的組合路徑來達到相同的目標產物。其反應可由芳香環與2-雜原子取代苯甲醛或雜環取代醛在酸性條件下與有機膦試劑來進行合成。此經過設計的有機鏻鹽成亦功的經由敝實驗室的主要合成策略進行分子內 Wittig 反應,並得以高產率得到傳統需利用交叉耦合反應來合成的多種雙聯雜環(例如indole-benzofuran/indole-benzothiophen/indole-indole/pyrrole-benzofuran/thiophene-benzofuran),提供給欲合成此類產物的對象一種替代合成方案。 第二章 新型全碳 1,3-偶極體前驅物 3-Homoacyl Coumarin 用於鏡像選擇性 (3+2) 協同環化反應合成 Herbertenolide 衍生物之應用 地錢所分離出的天然物中,倍半萜烯 Herbertane 這類具有獨特生物活性的物質(例如抗菌或促進神經組織增生等性質)已經吸引許多科學家去對其進行研究。而其天然物或衍生物的合成亦為其重要議題之一,目前已有數個 herbertenolide 或其差向異構物的全合成以及其衍生物合成或其主要架構 tetrahydrocyclopenta[c]chromen-4-ones 的合成方法學研究被報導出來。然而,目前的策略遇到的困難是所需合成步驟較多或是所合成的物質取代基有限,使得合成的產物廣度受限,進而使得此類天然物的研究進展受到限制。因此,我們期望可以研發一類有效的合成方法學來進行 herbertenolide 衍生物的合成,特別是由環化反應來建構其環戊烷主架構的策略。 在各種類型的環化反應策略中,1,3-偶極環化反應被認為是建構環的強力策略之一。目前可利用多元的1,3-偶極試劑來建構多種含雜原子之環狀化合物,例如pyrrolidine或isoxazolidine。但當想要以此策略合成全為碳原子組成之環,例如 cyclopentane 時,卻鮮少有適當的全碳 1,3-偶極試劑可以被拿來運用,大多數的1,3-偶極試劑都是含有雜原子的。因此我們希望可以開發出新型的全碳1,3-偶極試劑,並運用其進行 (3+2) 環化反應策略建構出以 cyclopentane 為核心的herbertenolide 衍生物。 在這本章中,我們提出對全碳1,3-偶極試劑的歸納與描述,並提出3-homoacylcoumarin作為一種新型的全碳1,3-偶極試劑前驅物。我們成功的利用此試劑與 indandione alkylidenes 在掌性有機催化劑的催化下進行立體選擇性的 (3+2) 合環反應來得到高鏡像選擇性且高產率的 herbertenolide 衍生物。除此之外,我們也做了詳細的機構探討並發現此反應共有兩個反應路徑同時進行,其中具有高立體選擇性的協同反應路徑相對速度極慢的逐步反應路徑來說主導了反應的進行。

並列摘要


CHAPTER- I Four-component Synthesis of Phosphonium Salts: Application toward an Alternative Approach to Cross-coupling for the Synthesis of bis-Heteroarenes Since almost a century, organophosphorus compounds are extensively used industrially as well as in synthetic organic laboratories. In particular, organophosphonium salts have a wide range of applications, especially for being as an important synthetic reagent for the Wittig reaction. During the development of the synthesis of different heterocycles via intramolecular Wittig reaction in our lab, we attempted to explore alternative methods for the generation of stable and isolable phosphonium salts that could further be employed in Wittig-type reactions for the synthesis of heteroarenes. In this chapter, a series of stable phosphonium salts have been synthesized via a novel four-component reaction of an arene nucleophile with 2-heteroatom substituted benzaldehyde or heteroaryl carboxaldehyde and phosphine in presence of an acid mediator. The phosphonium salts thus obtained were utilized for the synthesis of a variety of bis-heteroarenes, providing an efficient alternative method to the classical cross-coupling strategies. CHAPTER- II 3-Homoacyl Coumarins as a Class of All-Carbon 1,3-Dipole Precursor: An Enantioselective Concerted (3+2) Cycloaddition towards Herbertenolide Derivatives The significant biological properties of liverworts natural product herbertane sesquiterpenes catch the attention of scientists to discover the synthesis of them, such as hebertenolides. Several total synthesis and methodologies were developed toward the synthesis of hebertenolides or its main skeleton tetrahydrocyclopenta[c]chromen-4-ones. However, the steps for the synthesis or low substituent complexity of the resulting products restricted the discovery of this natural product. Thus, we expect to investigate an efficient methodology for the synthesis of herbertenolides derivatives, especially from a cycloaddition manner to construct the cyclopentane ring. Among the exploration of cycloaddition reactions, the applications of 1,3-dipoles have been considered as one of the powerful strategies for the ring construction. However, the construction of cyclopentane ring is relied on the contribution of all-carbon 1,3-dipoles which are scarcely reported to undergo cycloadditions when compared to the heteroatom-containing ones. In this chapter, we report a new type of all-carbon 1,3-dipole precursor, 3-homoacylcoumarin, which was employed for the stereoselective (3+2) cycloaddition with indanedione alkylidenes to generate a series of enantiopure herbertenolide derivatives in excellent yields. The structure is constructed of coumarin/spiro-indanedione fused cyclopentanes bearing four contiguous stereogenic centers. Moreover, the detailed mechanistic investigation revealed there are two reaction pathways progressed simultaneously, that a highly efficient stereoselective concerted route dominated the extremely slow stepwise pathway.

參考文獻


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