Study On Diesterification And Amidation Catalyzed By Deep Eutectic Solvents

Diester and amide compounds are very important fine chemicals and have been widely used in drug synthesis and fine chemical intermediates.The traditional synthesis methods of diesters and amides are accompanied by the discharge of waste acid and the use of a large number of organic solvents.It is of great significance to develop new green synthesis methods.As a recyclable,non-toxic,biodegradable,cheap and easily available green solvent,DESs has achieved good results in addition reactions,multi-component reactions,condensation reactions,coupling reactions and various other reactions.However,the application of DESs in diesterification and amidation reactions is rarely reported.Therefore,this paper used DESs as catalyst and solvent to carry out the synthesis of diesters and amides,respectively.In this paper,Br?nsted acid DESs,Lewis acid DESs and alkaline DESs were synthesized,and the effect of Br?nsted acid DESs and Lewis acid DESs on the diesterification reaction was studied.The diester products will be automatically separated from the reaction system of DESs in the reaction process,by adjusting the ratio of acid and alcohol,taking advantage of the difference of solubility of single ester product and diester product in DESs,and promoting the reaction to move forward.The maximum yield of diester product was up to 95%.The optimal condition was as follows: Ch Cl/PTSA(1:2)as DESs(0.2 equiv,)at 90 ℃ for 6 h.After substrate expansion,the reaction was suitable for most of the binary carboxylic acids,with high yield of primary alcohols(over 95%),medium yield of secondary alcohols(about70%),and no reaction of tertiary alcohols.DESs remained highly active after 8 cycles.In addition,the amidation reaction of carboxylic acids with urea was also studied in DESs The optimal condition was as follows: imidazole/urea(1:1)as DESs(1 equiv,)at120 ℃ for 18 h.The amidation reaction of aliphatic carboxylic acids proceed smoothly to afford desired products in good yields.However,the reaction of aromatic carboxylic acids gave amidation products in moderate yields.The yield remained above 80% yield after 5 cycles.