Wittig reaction之應用：呋喃香豆素及具有呋喃取代香豆素分子之合成
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2011
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本論文主要在探討經由分子內 Wittig reaction 來合成呋喃香豆素以及具有呋喃取代之香豆素分子。呋喃香豆素為香豆素眾多衍生物中重要的一群，其廣泛的藥學活性、光化學以及光物理性質吸引了許多科學家的高度注意。值得一提的是，目前對於呋喃并於吡喃酮之結構異構物 furo[3,4-c]coumarin 的合成研究報導較少。於是我們藉由使用三丁基磷對香豆素衍生物48進行共軛加成，接著加入醯氯試劑50進行醯化反應，最後利用三乙基胺做為鹼試劑進行去質子化以產生 phosphorus ylide 作為中間體來進行分子內 Wittig reaction 進而合成呋喃香豆素52。
此外，我們也將相似的合成條件應用至 coumarin-chalcone 的混成物56及63以探討三丁基磷進行共軛加成的化學選擇性；在大部分的例子中，我們僅獲得了具呋喃取代之香豆素分子57和64的結果顯示其選擇性極佳。我們也針對呋喃分子57進行光物理性質（吸收及螢光）的測量，並對其紅位移現象以及量子產率加以描述。
The article mainly focuses on the synthesis of highly functionalized furo[3,4-c]coumarins and coumarins bearing furan moieties via intramolecular Wittig reaction. As an important class of coumarin derivatives, furocomarins have attracted much attention to scientists because of their broadly pharmalogical, photochemical, and photophysical properties. It is noteworthy that the study on a general synthetic method for furo[3,4-c]coumarins which is one of constitutional isomers if the furan fuses on the pyrone has seldomly been reported. According to our protocol, highly functionalized furo[3,4-c]coumarins 52 can be prepared via the Michael addition of Bu3P toward substituted coumarin derivatives 48, acylation by acyl chlorides 50, deprotonation by Et3N, and finally intramolecular Wittig reaction using phosphorus ylide as presumable intermediates. In addition, the coumarin-chalcone hybrids 56 and 63 were investigated to understand the chemoselectivity of the Michael addition of Bu3P under our reaction condition. The results demonstrate that the chemoselectivity is excellent in mostcases, and coumarins bearing furan moieties 57 and 64 were furnished as the only products (no formation of their isomers). The photophysical properties (UV absorption and fluorescence) measurement of 6-bromo-3-(2-furyl)-coumarins 57 were carried out, and their redshift phenomena and quantum yields were also described.
The article mainly focuses on the synthesis of highly functionalized furo[3,4-c]coumarins and coumarins bearing furan moieties via intramolecular Wittig reaction. As an important class of coumarin derivatives, furocomarins have attracted much attention to scientists because of their broadly pharmalogical, photochemical, and photophysical properties. It is noteworthy that the study on a general synthetic method for furo[3,4-c]coumarins which is one of constitutional isomers if the furan fuses on the pyrone has seldomly been reported. According to our protocol, highly functionalized furo[3,4-c]coumarins 52 can be prepared via the Michael addition of Bu3P toward substituted coumarin derivatives 48, acylation by acyl chlorides 50, deprotonation by Et3N, and finally intramolecular Wittig reaction using phosphorus ylide as presumable intermediates. In addition, the coumarin-chalcone hybrids 56 and 63 were investigated to understand the chemoselectivity of the Michael addition of Bu3P under our reaction condition. The results demonstrate that the chemoselectivity is excellent in mostcases, and coumarins bearing furan moieties 57 and 64 were furnished as the only products (no formation of their isomers). The photophysical properties (UV absorption and fluorescence) measurement of 6-bromo-3-(2-furyl)-coumarins 57 were carried out, and their redshift phenomena and quantum yields were also described.
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呋喃香豆素, 共軛加成, 香豆素, Wittig reaction, furocoumarin