利用有機磷試劑經由分子內 Wittig 反應合成三取代呋喃化合物及其在 α,β-不飽和亞胺化合物上之反應性探討
Abstract
本論文分成兩大主題,第一主題為三取代基呋喃化合物之合成,以及第二主題是利用α,β-不飽和亞胺經由有機磷試劑在高溫環境下反應之探討:
具有多取代基的呋喃化合物在有機合成中佔有很重要的角色,因此本實驗室在去年開發出一種新穎的合成方法製備具有四取代基之呋喃化合物;而現在本實驗室延續此合成方法並做適當的修飾,開發出合成具有三取代基的呋喃化合物。反應先將三丁基磷與醯氯62加到反應瓶中,之後再將起始物76作為Michael addition的受體加入反應瓶,最後再加入三乙基胺,在室溫下反應10分鐘到40小時,可得到具有三個取代基之呋喃化合物79,產率在24-93%之間。我們推測合成路徑為三丁基磷先對化合物76先進行Michael addition反應,形成兩性離子中間化合物77,接著醯氯62與中間體77進行醯化反應後,形成的中間化合物81進行去質子化反應,生成的化合物78經過分子內Witting反應,即可得到呋喃化合物79。
我們也試著利用類似的方法開發多取代的吡咯化合物;首先利用四氯化鈦試劑與胺試劑及我們現有的酮試劑進行縮和反應,先合成出目標起始物亞胺試劑,接著依序加入目標磷試劑、醯氯試劑62以及三乙基胺進行反應,然而可惜反應效率不如我們預期的理想;之後使用化合物163b於高溫下進行反應十九個小時,意外拿到產物165ba。我們也有試著針對產物165ba的合成進行一連串的最佳化篩選,然而可惜最後發現反應過程中的中間體似乎不太穩定,導致合成165ba時所得到最佳產率並不具有再現性,而我們也試著推測其合成路徑,首先由三丁基磷先對起始物163b進行1,4-addition,接著再進行N-acylation成中間產物171,之後由鹼試劑去質子化後進行acyl substitution將化合物重排成中間產物173,接著電子重排脫去磷試劑就可得到中間產物174,接著進行去質子化、電子重排後再進行1,2-addition以及質子化就可得到中間化合物177,最後再進行互變異構化就可得到目標產物165ba。
The dissertation is divided into two parts : synthesis of trisubstituted furans (part I) and investigation of the reaction of the α,β-unsaturated imines and alkyl phosphine reagents (part II). Part I: Multi-substituted furans have important application in organic synthesis. A facile preparation of trisubstituted furans stating from the Michael acceptors 76, tributylphosphine, triethylamine and acyl chlorides 62, is realized according to our protocol. Various highly functional furans can be prepared in very mild condition (rt) within 10 min to 40 h in moderate to high yields (24-93%). The reaction mechanism is proposed to undergo the Michael reaction of Bu3P and 76 followed by acylation with 62, deprotonation of the corresponding intermediate 81, and finally an intramolecular Wittig reaction of 79. We also try to apply the similiar concept (the key step: Intramolecular Wittig reaction) in the synthesis of multi-substituted pyrroles. The reaction of the α,β-unsaturated imine (163b) to react with Bu3P, PhCOCl, and Et3N takes place at 80 oC for 19 h, leading to the unexpected product 165ba. The result of 165ba is not reproducible, probably due to the instability of the reaction intermediate. The reaction mechanism is proposed to undergo the 1,4-addition reaction of Bu3P toward 163b followed by acylation with 62, deprotonation of the corresponding intermediate 171, and then acyl substitution to furnish the intermediate 173. The elimination of Bu3P from the intermediate 173 proceeds to provide the intermediate 174, which then undergoes deprotonation, electronic-rearrangement, 1,2-addition, and protonation to give the intermediate 177ba. Finally, 165ba is afforded via the tautomerization of 177ba.
The dissertation is divided into two parts : synthesis of trisubstituted furans (part I) and investigation of the reaction of the α,β-unsaturated imines and alkyl phosphine reagents (part II). Part I: Multi-substituted furans have important application in organic synthesis. A facile preparation of trisubstituted furans stating from the Michael acceptors 76, tributylphosphine, triethylamine and acyl chlorides 62, is realized according to our protocol. Various highly functional furans can be prepared in very mild condition (rt) within 10 min to 40 h in moderate to high yields (24-93%). The reaction mechanism is proposed to undergo the Michael reaction of Bu3P and 76 followed by acylation with 62, deprotonation of the corresponding intermediate 81, and finally an intramolecular Wittig reaction of 79. We also try to apply the similiar concept (the key step: Intramolecular Wittig reaction) in the synthesis of multi-substituted pyrroles. The reaction of the α,β-unsaturated imine (163b) to react with Bu3P, PhCOCl, and Et3N takes place at 80 oC for 19 h, leading to the unexpected product 165ba. The result of 165ba is not reproducible, probably due to the instability of the reaction intermediate. The reaction mechanism is proposed to undergo the 1,4-addition reaction of Bu3P toward 163b followed by acylation with 62, deprotonation of the corresponding intermediate 171, and then acyl substitution to furnish the intermediate 173. The elimination of Bu3P from the intermediate 173 proceeds to provide the intermediate 174, which then undergoes deprotonation, electronic-rearrangement, 1,2-addition, and protonation to give the intermediate 177ba. Finally, 165ba is afforded via the tautomerization of 177ba.
Description
Keywords
有機磷試劑, Wittig 反應, 三取代呋喃化合物, α, β-不飽和亞胺化合物