Study Of Bio-based DES As Reaction Media For Aromatic Nucleophilic Fluorination And Esterification Of Alkyl Halides With Carboxylic Acids (Salts)

It is an important work to seek non-toxic media to replace the traditional organic solvents in the concept of green chemistry.Ionic liguids(ILs) have attracted considerable attention for its recyclability and low emission,however,their widespread application are limited by complicated preparation,high cost,toxicological and low bio-degradability.Deep eutectic solvent(DES),especially bio-based DES are now rapidly emerging as new green solvent in the current literature. Besides the advantages of ILs, DES also have other great virtue like facile preparation,low price,non-toxic and biodegradable. This article study the application of bio-based DES as reaction media for aromatic nucleophilic fluorination and esterification of carboxylic acids (salts) with alkyl halides. We wish to extend and enrich the application scope of bio-based DES as green reaction media.The first chapter investigates bio-based DES(choline chloride:urea) as reaction media for aromatic nucleophilic fluorination of halogenated aromatics with KF.Based on the study of kinds of DES,ratio, reaction temperature etc on the product yields we find the best reaction conditions as follows:choline chloride:urea(1:2), DMSO as solvent, KF(5 equiv), reaction temperature(160℃). On such basis,the aromatic nucleophilic fluorination of a series of 18 halogenated aromatics with KF are conducted. Besides a few of them are affected by steric effect of ortho-substituent, most fluorinated aromatics with strong electron-withdrawing group can be obtained in the yields of 80～100%.These results show that bio-based DES(choline chloride:urea) can replace ILs totally as reaction media for aromatic nucleophilic fluorination of halogenated aromatics with KF, and this method could be popularized with the advantage of economic and environmental.The second chapter investigates bio-based DES(choline chloride:urea) as reaction media for alkyl halides with carboxylic acids (salts).Based on study of the effect of influencing factor on the reaction,we find alkyl halides, carboxylic acids and sodium hydroxide can be reacted in one-pot under the participation of DES(choline chloride:urea).The esterification of a series of 17 carboxylic acids with benzyl chloride are conducted. After one hour, carboxylic ester can be obtained in high yield of above 95% under temperature of 90℃.Furthermore, when we replace sodium hydroxide with triethylamine,the reaction can be conducted under temperature of 60 ℃. The esterification of a series of 20 carboxylic acids with alkyl halides are conducted with high yields of above 95% and DES can be recycled 5 times.This method offers marked improvements in the terms of cheap and available materials,moderate reaction conditions,high isolated yields, security,simple operation and recyclability of solvent.