隨著環保意識的高漲，以具有揮發性低、不易燃及回收容易等特性的“綠色溶劑”－離子熔液取代傳統有毒、揮發性高的有機溶劑是必然的趨勢。近年來，室溫離子熔液已被廣泛應用於合成反應中，並且已經可以達到與在一般有機溶劑中進行反應的同等效果甚至更佳。費希爾Indole反應是少數進行分子內環合的反應之一，目前廣泛被應用來製備生物鹼及天然物，但其反應條件較劇烈，且所使用的催化劑量大、回收不易等問題增加了費希爾Indole反應應用的困難度。
本篇論文使用EMI-BF4-ZnCl2和EMIC-ZnCl2兩種對空氣與水穩定的室溫離子熔液作為費希爾Indole反應的溶劑暨催化劑，並探討催化劑量、反應溫度、反應時間及產率的關係。我們成功地在此兩種離子熔液中合成出Indole化合物，且可利用萃取的方式將產物取出，離子熔液可回收重複使用至少四次，而產率並無減少的現象，以此證明，費希爾Indole反應亦可利用EMI-BF4-ZnCl2及EMIC-ZnCl2兩種“綠色溶劑”作為反應環境。

In the search of cleaner technologies for chemical synthetic alternative to toxic, volatile organic solvents is a particularly important goal. Room-temperature ionic liquids which are nonvolatile, inflammable, and have good solvation power, have attracted a lot of recent attention as a “green solvent”. Fischer indole synthesis has been one of the few heterocyclic synthesis studied in great detail. This is due to its versatility and broad applicability in the synthesis of a number of biologically active natural and synthetic products. However, Fischer indole synthesis almost proceeded at high temperature and needed a very large amount of catalysts which are environmentally unfriendly, hazardous or difficult to handle.
In this study, we report the Fischer indole synthesis in EMI-BF4-ZnCl2 and EMIC-ZnCl2 ionic liquids which air- and moisture-stable ionic liquids. We found that ionic liquid can be used in Fischer indole reactions successfully, and the ionic liquids can be reused at least four times with no noticeable drop in activity or yield and the products are simply removed from the reaction mixture by extraction.

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