The Application Of Cholinium-based Ionic Liquids In The Catalytic Synthesis Of Indole Derivatives

The traditional chemical industry which was first pollution and control after it had destroyed theenvironment seriously. The idea of green chemistry which want to control and eliminate pollutions at thevery beginning using the chemical principles attracted widely attention since it is proposed at the end of thelast century. Green chemistry is a new stage in the development of chemistry for mankind, which isbelieved to be able to solve pollution problems in the chemical industry and achieve sustainable economicand social development. Ionic liquids and their utilization have become an important research area of greenchemistry. Ionic liquids are novel solvent, catalysts and soft materials with non-volatile, wide liquid range,strong solubility, good thermal stability, adjustable structure and many other advantages, and have shownvarious applications under the background of green chemistry.As a part of the National Natural Science Foundation of China(NO.21373079), a series ofcholine-based ionic liquids are designed and synthesized, and their utilization in the catalytic synthesis ofdifferent indole derivatives were investigated. The details are given as follow:1. Choline chloride(ChCl) and its deep eutectic mixtrures with ethylene glycol is found to be able tocatalyze Friedel–Crafts alkylation reactions of indole with benzaldehyde for the synthesis of bis(indolyl)methane. Choline chloride as a catalyst can well catalyz electrophilic substitution reaction of benzaldehydeand indoles for synthesis of bis(indolyl)methane. This catalytic system has wide substrates tolarance, mildreaction conditions and the catalyst can be recovered and recycled for at least five times without activitydecrease. In addition, the catalytic mechanism is also proposed based on the capture and identification ofthe intermediate products.2. The catalytic performance of different choline based ionic liquids on the "one-pot" reaction amongbenzaldehyde, indole, and malononitrile under solvent-free conditions is investigated. It is found that basicionic liquids have good catalytic activity, and [DMEA][Ac] has the highest catalytic activity. The effect ofthe amount of catalyst and reaction temperature on reaction are also studied, and under the optimizedreaction conditions, the substrate tolerance is discussed. This catalytic system benefit from good catalyticactivity, wide substrates tolarance, and mild reaction conditions. 3. The catalytic performance of choline based ionic liquids for the Mannich reaction amongbenzaldehyde, indole and pyrrolidine is investigated. It is found that the cheap and feasible choline chlorideis effective in promoting such reactions. This catalytic system has broad substrate tolarance, and the acidsensitive groups can be well kept. In addition, this catalyst has good biocompatibility and can be easilyrecycled.4. The different catalytic performances of a series of basic ionic liquids for three-component “one-pot”reaction of benzaldehyde, indole and4-hydroxycoumarin are investigated. The aqueous solution of cholinehydroxyl is found to be effective in promoting such reactions, and the target compounds exhibit goodresponses to the pH variations of the solution.