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  • 學位論文

環丙烯衍生物之歧化反應: 聚合物自我修復反應機構之發現

Metathesis of Cyclopropene Derivatives: Discovering Self-Healing Mechanism in Polymer Synthesis

指導教授 : 陸天堯

摘要


含有張力之環狀分子,如降冰片烯及環丁烯之衍生物,已廣泛的作為開環歧化反應之研究對象。然而,環丙烯及其衍生物則相對地較少被研究。過去本實驗室成功地利用了降冰片烯及環丁烯之衍生物合成出相對應高度規則的單股高分子及梯番。其中我們發現了苯胺基團是得到高度規則結構的必要條件,依循此規則,我們設計並且合成了包含苯胺基團的環丙烯衍生物,並用其作為後續研究的對象。 費雪碳烯一直以來被認為擁有較低的反應性,而其對於環丙烯衍生物的開環交叉複分解反應的實驗顯示出即使擁有較低的反應性,費雪碳烯仍然能夠催化這類的反應,並且得到目標產物乙烯基及烷氧基取代乙烯基之雙烯高達85%的產率。其中,沒有任何的寡聚物或是聚合物被觀測到,這樣的結果能夠透過前緣分子軌域的分析去了解其成因。這是由於苯胺基團會對分子軌域的係數分布以及能量高低造成擾動,進而影響到整個反應的化學選擇性。 另一方面,環丙烯衍生物的開環岐化聚合反應也在本篇論文裡面被探討。當聚合反應由第一代格拉布催化劑催化時,會產生線型的高分子。此外,該線型高分子之雙鍵皆為反式,這樣的結果可以由我們首先提出的「自我修復」反應機制去解釋。其中,所有的順式雙鍵皆會透過分子內關環岐化反應而移出高分子骨架。而當反應由第二代格拉布催化劑催化時,不同於先前所述,我們會得到分子量高出預期的環狀聚合物。其中,在核磁共振光譜中無法觀測到任何的末端基團吸收峰,且其他的訊號皆為尖銳且對稱的吸收峰,顯示出其高度對稱且環狀的結構。 由於二維高分子的獨特性質,這類的高分子在近年來受到高度的重視,然而對於這樣的高分子,目前現有的合成手段仍相當有限。雙環丙烯衍生物在進行開環岐化聚合反應之後所產生的高分子能夠在石墨的表面上排成接近1000平方奈米的大小。而在其中,兩種不同的形態能在平面上被看到,其中一種是條狀的形式,而另一種是交錯的形式。這樣的聚合反應能夠在相對不嚴苛的反應條件下進行,而這樣的策略很有可能能夠作為一種合成新的二維高分子的一種手段。

並列摘要


In contrast to many cyclic strain olefins such as norbornene and cyclobutene, studies on metathesis of cyclopropene are relatively less extensive. In line with previous work in our laboratory, following the same design concept, monomers with N-aryl pendant and azaspiro[2.3]hex-1-ene was designed and synthesized. Fischer type carbenes have been considered as relatively less reactive carbenes compared with ruthenium alkylidenes, but they can still trigger metathesis reactions. The ring opening cross metathesis (ROCM) reactions of cyclopropene derivatives catalyzed by Fischer type carbenes were accomplished. Despite the lower reactivity, the reaction proceeded well, giving desired alkoxy-substituted ring opened products in up to 85% yield. The presence of aniline moiety would perturb the HOMO/LUMO energy levels and the coefficients of molecular orbitals, which played a crucial role in the chemoselectivity of ROCM. ROMPs of azaspiro[2.3]hexene derivatives catalyzed by Grubbs’ first and second generation catalyst were examined. Linear polycyclopropenes with exclusive E-configuration was achieved by using Grubbs’ first generation catalyst. The predominant E-double bonds were rationalized by the unprecedented ‘self-healing’ mechanism, which would remove Z-double bonds from polymer backbones. In addition, cyclic polymers with high Mn were obtained when Grubbs’ second generation catalyst was employed. The absence of end groups and the very sharp singlet absorptions strongly indicated the cyclic architecture. Lastly, 2D polymers have received a great deal of attention recently due to their potential applications, but the synthetic methods for 2D polymers are still limited. The ROMP of bis(cyclopropene) derivatives were briefly investigated. The resultant polymers revealed regular lateral alignments on graphite surface with areas up to 1000 nm2, in which two kinds of morphologies including stipe-like and zig-zag patterns were observed. The polymerization was performed in solution phase and ambient conditions, which may serve as a promising strategy for synthesis of 2D polymers.

參考文獻


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34. Unpublished results performed by professor Yu-Ying Lai.

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